Name: assessment of dictyostelium discoideum response to acute mechanical stimulation
Uploaded: 2017-11-09T12:30:00.000+00:00
Duration: 10 min 40 s
Description: Watch this Scientific Journal Video about Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation at JoVE.com

This work was supported by National Institutes of Health grant R35 GM118177 to PND.

<ol>
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The authors have nothing to disclose.

The methods described here offer a convenient way to assess both population and individual cell behavior in response to shear flow. Importantly, while previous studies analyzed localization of leading and lagging edge markers during migration, the current approach allows investigation of immediate effects by applying the shear flow acutely. Using this method we demonstrated that, in fact, the initial response of cells to shear flow does not require cell migration. Instead, the rapid and transient response to the initial ...

Migration of eukaryotic cells is biased by diverse chemical and physical cues in the environment, including gradients of soluble or substrate-bound chemoattractants, variable stiffness of the substrates, electric fields, or shear flow. Although there have been many advances in our understanding of the molecular mechanisms driving chemotaxis, less is known about other types of directed migration and how these diverse signals are integrated at the cellular level to produce a unified migratory response.
Directed migration toward an increasing concentration of a chemoattractant involves three behavioral components: motility, directional sensing, and polarity1. Motility refers to random movement of cells achieved by pseudopod protrusion. Directional sensing is the ability of a cell to detect the source of a chemoattractant, which can occur even in immobilized cells. Polarity refers to the more stable asymmetrical distribution of intracellular components between the leading and lagging edge of a cell, which leads to increased persistence in movement.
Cellular response to a chemoattractant depends on the activity of four conceptually defined regulatory networks: receptor/ G protein, signal transduction, actin cytoskeleton, and polarity1. Chemoattractant binding to the G protein-coupled receptor transmits the signal via heterotrimeric G proteins &#945; and &#946;&#947; to the downstream signal transduction network, which amplifies the directional signal. Multiple pathways within the signal transduction network act in parallel and feed into the actin cytoskeleton network to bias actin polymerization, and consequent pseudopod protrusion, in the direction of the gradient. Among important regulators of chemotaxis are Ras GTPase, TorC2, phosphoinositide 3-kinase (PI3K), phosphatase and tensin homolog (PTEN), and guanylyl cyclase. Feedback mechanisms within the signal transduction network and between the signal transduction and actin cytoskeleton networks further amplify the response. Finally, the poorly defined polarity network receives input from the actin cytoskeleton, and further biases the signal transduction network to promote persistent migration in the direction of the gradient.
Much of our mechanistic understanding of chemotaxis was made possible because of the development of fluorescently-tagged biosensors for various components of the regulatory networks. Many chemotaxis regulators have an asymmetrical distribution either of the regulatory molecule itself or its activity. For example, biosensors that recognize activated versions of small GTPases Ras and Rap1 &#8211; Ras-binding domains of Raf1 (referred to as RBD here) and RalGDS, respectively &#8211; localize to the leading edge of a chemotaxing cell2,3. Similarly, PI3K and its product phosphatidylinositol (3,4,5)-trisphosphate (PIP3), recognized by a pleckstrin homology (PH) domain, also show localization at the front of a cell4,5. In contrast, a 3-phosphatase PTEN, which converts PIP3 back to phosphatidylinositol (4,5)-bisphosphate, localizes to the lagging edge of the cell6. Importantly, these biosensors change their localization in response to global stimulation with a chemoattractant. Leading edge markers, which are cytosolic or on the tips of protrusions in a resting cell, relocalize to the cortex, whereas lagging edge markers, which have cortical localization and are absent from the tips of protrusions in a resting cell, become cytosolic after stimulation. Analysis of biosensor distribution in response to global stimulation with a chemoattractant minimizes the contribution of motility and polarity, which often confound the observations. Global or uniform stimulation of a cell suspension with a chemoattractant is also used as a tool to assess population-wide changes in protein activation, often detected by protein phosphorylation7,8,9. This biochemical assay is primarily used to obtain temporal information, whereas microscopy is used to gather both temporal and spatial information about the behavior of various components of the regulatory networks.
The signal transduction network incorporates features of an excitable system10,11. Responses to supra-threshold chemotactic stimuli are &#34;all-or-none&#34; and display refractory periods. Responses are also triggered stochastically and can show oscillatory behavior. Signal transduction events are localized to regions of the cortex that propagate as waves12,13,14,15. Front, or back, markers are recruited to, or dissociate from, the active zones of the propagating waves. Due to the refractory region trailing the active zone, the oppositely directed waves annihilate as they meet. The propagating signal transduction waves underlie the cellular protrusions that mediate cell migration10.
Much of the aforementioned information on chemotaxis came from the studies on the social amoeba Dictyostelium discoideum, although similar regulatory mechanisms are also applicable to neutrophils and other mammalian cell types16. Dictyostelium is a well-established model organism that has a robust chemotactic response during starvation, when thousands of single cells migrate toward an aggregation center, eventually forming a multicellular fruiting body containing spores. Chemotaxis is also essential during the single-cell growth stage of this organism for locating bacterial food sources. Importantly, migration of single Dictyostelium cells is remarkably similar to the migration of mammalian neutrophils or metastatic cancer cells, all of which undergo very rapid amoeboid-type migration. In fact, both the overall topology of the regulatory networks, as well as many of the individual signal transduction pathways involved in chemotaxis are conserved between Dictyostelium and mammalian leukocytes17. Furthermore, other cells, such as fibroblasts, use receptor tyrosine kinases (RTK) instead of GPCRs; however, RTKs may feed into similar networks.
In contrast to chemotaxis, thorough understanding of the signaling mechanisms that drive various other modes of directed migration is lacking. Similarly to cells migrating in a chemoattractant gradient several studies have reported activation and/or localization of typical leading edge markers, including actin polymerization, PIP3 and/or extracellular signal-regulated kinase (ERK) 1/2, at the front of cells undergoing directed migration in response to shear flow or changes in electric fields18,19,20,21. However, in these studies continuous exposure to the stimulus also resulted in cell migration, leaving open the question whether, for example, the leading edge markers localize specifically in response to a stimulus, or if they simply localize at the leading edge because of increased number of pseudopods at the front of a migrating cell.
We developed assays that allow us to observe the response of cells to acute mechanical perturbation delivered as shear flow both at the population level and as individual cells22. Similar to global stimulation with a chemoattractant, acute stimulation with shear flow allows the study of a cellular response to a mechanical stimulus without the confounding contribution from motility or polarity. Combining these biochemical and microscopic assays with genetic or pharmacological perturbations allows us to learn about how mechanical stimuli are perceived and transmitted. Moreover, this approach also provides a novel method for tapping into the system downstream of the chemoattractant receptor in the absence of a chemoattractant, thereby isolating the signal transduction and actin cytoskeleton networks from the receptor/G protein network.
Using the techniques described below we recently demonstrated that acute shear stress leads to activation of multiple components of the chemotactic signal transduction and actin cytoskeleton networks22. By applying the acute mechanical stimulus at varying intervals, we demonstrated that, similarly to chemoattractants, response to mechanical stimuli also exhibits features of an excitable system, including the all-or-none behavior of the response under saturating conditions and the presence of a refractory period. Finally, by combining mechanical and chemical stimulation we showed that the two stimuli share signal transduction and actin cytoskeleton networks, which likely allow for integration of multiple stimuli to bias cell migration.

<table><tbody><tr><td>&lt;strong&gt;Reagents&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Dextrose</td><td>Fisher</td><td>D16-1</td><td>Use to prepare HL-5 media and SM plates (steps 1.1, 1.2)</td></tr><tr><td>Proteose peptone</td><td>Fisher</td><td>DF0120-17-6</td><td>Use to prepare HL-5 media (step 1.1)</td></tr><tr><td>Yeast extract</td><td>Fisher</td><td>50-550-445</td><td>Use to prepare HL-5 media and SM plates (steps 1.1, 1.2)</td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;&amp;middot;7H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Fisher</td><td>S373-500</td><td>Use to prepare HL-5 media, and 10X Phosphate Buffer (steps 1.1, 1.3)</td></tr><tr><td>KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;</td><td>Fisher</td><td>P386-500</td><td>Use to prepare HL-5 media, SM plates, and 10X Phosphate Buffer (steps 1.1-1.3)</td></tr><tr><td>Streptomycin (dihydrostreptomycin sulfate)</td><td>Fisher</td><td>ICN10040525</td><td>Use to prepare HL-5 media (step 1.1)</td></tr><tr><td>Peptone (Bacto)</td><td>Fisher</td><td>DF0118-17-0</td><td>Use to prepare SM plates (step 1.2)</td></tr><tr><td>K&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;</td><td>Fisher</td><td>P288-100</td><td>Use to prepare SM plates (step 1.2)</td></tr><tr><td>Agar</td><td>Fisher</td><td>BP1423-500</td><td>Use to prepare SM plates (step 1.2)</td></tr><tr><td>MgSO&lt;sub&gt;4&lt;/sub&gt;</td><td>Fisher</td><td>M65-500</td><td>Use to prepare DB Buffer (step 1.4)</td></tr><tr><td>CaCl&lt;sub&gt;2&lt;/sub&gt;</td><td>Fisher</td><td>C79-500</td><td>Use to prepare DB Buffer (step 1.4)</td></tr><tr><td>Caffeine</td><td>Fisher</td><td>O1728-500</td><td>Use to prepare caffeine (step 1.5)</td></tr><tr><td>cAMP (EMD Millipore Calbiochem Adenosine 3 ft.,5 ft.-cyclic Monophosphate, Sodium Salt)</td><td>Fisher</td><td>11-680-1100MG</td><td>Use to prepare cAMP (step 1.6)</td></tr><tr><td>Folic acid</td><td>Sigma</td><td>F7876</td><td>Use to prepare folic acid (step 1.7)</td></tr><tr><td>Tris base</td><td>Fisher</td><td>BP152-500</td><td>Use to prepare 3X sample buffer (step 1.8)</td></tr><tr><td>Sodium dodecyl sulfate (SDS)</td><td>Fisher</td><td>BP166-500</td><td>Use to prepare 3X sample buffer (step 1.8)</td></tr><tr><td>Glycerol</td><td>Fisher</td><td>G33-500</td><td>Use to prepare 3X sample buffer (step 1.8)</td></tr><tr><td>Dithiothreitol (DTT)</td><td>Bio-Rad</td><td>1610610</td><td>Use to prepare 3X sample buffer (step 1.8)</td></tr><tr><td>Bromophenol blue</td><td>Bio-Rad</td><td>1610404</td><td>Use to prepare 3X sample buffer (step 1.8)</td></tr><tr><td>NaF</td><td>Fisher</td><td>S299-100</td><td>Use to prepare sample buffer with protease and phosphatase inhibitors (step 1.8)</td></tr><tr><td>Na&lt;sub&gt;3&lt;/sub&gt;VO&lt;sub&gt;4&lt;/sub&gt;</td><td>Fisher</td><td>50-994-911</td><td>Use to prepare sample buffer with protease and phosphatase inhibitors (step 1.8)</td></tr><tr><td>Sodium pyrophosphate decahydrate</td><td>Fisher</td><td>S390-500</td><td>Use to prepare sample buffer with protease and phosphatase inhibitors (step 1.8)</td></tr><tr><td>Complete EDTA-free protease inhibitor cocktail (Roche)</td><td>Sigma</td><td>11873580001</td><td>Use to prepare sample buffer with protease and phosphatase inhibitors (step 1.8)</td></tr><tr><td>Latrunculin A</td><td>Enzo Life Sciences</td><td>BML-T119-0100</td><td>Use to prepare Latrunculin A (step 1.9)</td></tr><tr><td>4-15% Tris-HCl polyacrylamide gel</td><td>Bio-Rad</td><td>3450029</td><td>Use for immunoblotting (step 3.3)</td></tr><tr><td>Polyvinylidene fluoride membrane</td><td>Bio-Rad</td><td>1620177</td><td>Use for immunoblotting (step 3.3)</td></tr><tr><td>Phospho-PKC (pan) (zeta Thr410) (190D10) Rabbit antibody</td><td>Cell Signaling</td><td>2060</td><td>Primary antibody for use in immunoblotting (step 3.3)</td></tr><tr><td>Phospho-p44/42 MAPK (Erk1/2) (Thr202/Tyr204) (D13.14.4E) XP antibody</td><td>Cell Signaling</td><td>4370</td><td>Primary antibody for use in immunoblotting (step 3.3)</td></tr><tr><td>Rabbit IgG HRP Linked Whole Ab (from Donkey)</td><td>GE Healthcare</td><td>NA934-100UL</td><td>Secondary antibody for use in immunoblotting (step 3.3)</td></tr><tr><td>Enhanced chemiluminescence substrate (Clarity Western ECL Substrate)</td><td>Bio-Rad</td><td>1705060</td><td>Use for immunoblotting (step 3.3)</td></tr><tr><td>Stripping buffer (Restore Plus Western blot stripping buffer)</td><td>Pierce</td><td>PI46430</td><td>Use for immunoblotting (step 3.3)</td></tr><tr><td>Coomassie Brilliant Blue</td><td>Fisher</td><td>PI20278</td><td>Use for immunoblotting (step 3.3)</td></tr><tr><td>K. aerogenes strain (non-pathogenic)</td><td>Dicty Stock Center (dictybase.org)</td><td></td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Materials and Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Orbital shaker (model G-33, or a comparable alternative)</td><td>New Brunswick Scientific</td><td></td><td>Use to grow &lt;em&gt;K. aerogenes&lt;/em&gt; (step 2.1.1), and to basalate and stimulate &lt;em&gt;D. discoideum&lt;/em&gt; cells (step 3). The radius of gyration for this shaker is 9.5 mm.</td></tr><tr><td>10 cm Petri dish</td><td>Fisher</td><td>FB0875712</td><td>Use to prepare SM plates (step 1.2)</td></tr><tr><td>Hemocytometer</td><td>Fisher</td><td>02-671-51B</td><td>Use to count &lt;em&gt;D. discoideum&lt;/em&gt; cells (step 2.1.2)</td></tr><tr><td>35 mm dish (Corning Falcon Easy-Grip Tissue Culture Dish)</td><td>Fisher</td><td>08-772A</td><td>Use to plate &lt;em&gt;D. discoideum&lt;/em&gt;cells for mechanical stimulation followed by cell lysis (step 3.1.1)</td></tr><tr><td>Polystyrene cup (5 mL)</td><td>VWR</td><td>13915-985</td><td>Use to stimulate &lt;em&gt;D. discoideum&lt;/em&gt; cell suspension with a chemoattractant (step 3.2.2)</td></tr><tr><td>Fluidic unit with pump (ibidi Pump System)</td><td>Ibidi</td><td>10902</td><td>Use to deliver mechanical stimulation to &lt;em&gt;D. discoideum&lt;/em&gt; cells in a channel (steps 4.1, 4.2, and 5)</td></tr><tr><td>Slide with a channel (&amp;mu;-Slide III 3in1 ibiTreat: #1.5 polymer coverslip, tissue culture treated, sterilized)</td><td>Ibidi</td><td>80316</td><td>Use to plate &lt;em&gt;D. discoideum&lt;/em&gt; cells for mechanical stimulation delivered by a fluidic device (steps 4.1, 4.2, and 5)</td></tr><tr><td>50 mL reservoirs (Ibidi Reservoir Holder for Fluidic Unit)</td><td>Ibidi</td><td>10978</td><td>Use to setup the fluidic device for delivering mechanical stimulation to &lt;em&gt;D. discoideum&lt;/em&gt; cells in a channel (steps 4.1, 4.2, and 5)</td></tr><tr><td>Lines for the fluidic unit (Perfusion Set YELLOW-and-GREEN)</td><td>Ibidi</td><td>10964</td><td>Use to setup the fluidic device for delivering mechanical stimulation to &lt;em&gt;D. discoideum&lt;/em&gt; cells in a channel (steps 4.1, 4.2, and 5). Note: the two lines can also be cut from the 1.6 mm tubing (catalog number 10842).</td></tr><tr><td>Line for the drain (1.6 mm ID tubing)</td><td>Ibidi</td><td>10842</td><td>Use to setup the fluidic device for delivering mechanical stimulation to &lt;em&gt;D. discoideum&lt;/em&gt; cells in a channel (steps 4.1, 4.2, and 5).</td></tr><tr><td>Zeiss Observer.Z1 inverted microscope equipped with a 40X/1.3 oil objective and a 20X/0.3 air objective (or a comparable alternative)</td><td>Zeiss</td><td></td><td>Used to image &lt;em&gt;D. discoideum&lt;/em&gt; cells with phase-contrast or fluorescence illumination (steps 4 and 5)</td></tr><tr><td>UltraView spinning disk confocal microscope equipped with a 40&amp;times;/1.25&amp;ndash;0.75 oil objective (or a comparable alternative)</td><td>Perkin-Elmer</td><td>DM 16000</td><td>An alternative used to image &lt;em&gt;D. discoideum&lt;/em&gt; cells (step 4.1.4)</td></tr><tr><td>FemtoJet Microinjector (Eppendorf; model 5247, or a comparable alternative) with Eppendorf InjectMan</td><td>Eppendorf</td><td>5252000021D and 5192000027</td><td>Use to deliver mechanical stimulation to &lt;em&gt;D. discoideum&lt;/em&gt; cells by a micropipette (step 4.3). Note: catalog number are for the newest version of the equipment (4i).</td></tr><tr><td>Micropipette (Femtotip; 1 &amp;mu;m outside diameter, 0.5 &amp;mu;m inside diameter )</td><td>Eppendorf</td><td>930000035</td><td>Use to deliver mechanical stimulation to &lt;em&gt;D. discoideum&lt;/em&gt; cells by a micropipette (step 4.3)</td></tr><tr><td>Microloader tips (Eppendorf Femtotips Microloader Tips for Femtojet Microinjector)</td><td>Eppendorf</td><td>5242956.003</td><td>Use to fill the micropipette (femtotip) with buffer (step 4.3.1)</td></tr><tr><td>1-well chamber (Thermo Scientific Nunc Lab-Tek Chambered Coverglass)</td><td>Fisher</td><td>12-565-472</td><td>Use to plate &lt;em&gt;D. discoideum&lt;/em&gt; cells for mechanical stimulation delivered by a micropipette (step 4.3.2)</td></tr><tr><td>8-well chamber (Thermo Scientific Nunc Lab-Tek II Chambered Coverglass)</td><td>Fisher</td><td>12-565-338</td><td>Use to plate &lt;em&gt;D. discoideum&lt;/em&gt; cells for mechanical stimulation delivered by bulk buffer addition (step 4.4.1)</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Software&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Image Analysis Software (Fiji)</td><td>NIH</td><td>https://fiji.sc/</td><td>Use to quantify response to mechanical stimulation (step 4.5)</td></tr><tr><td>Migration analysis software (Tracking Tool PRO)</td><td>Gradientech</td><td>http://gradientech.se/tracking-tool-pro/</td><td>Use to quantify cell speed and persistence (step 5.4)</td></tr></tbody></table>

assessment of dictyostelium discoideum response to acute mechanical stimulation

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium discoideum revealed that a complex signal transduction network of parallel pathways amplifies the response to chemoattractants, and leads to biased actin polymerization and protrusion of a pseudopod in the direction of a gradient. In contrast, molecular mechanisms driving other types of directed migration, for example, due to exposure to shear flow or electric fields, are not known. Many regulators of chemotaxis exhibit localization at the leading or lagging edge of a migrating cell, as well as show transient changes in localization or activation following global stimulation with a chemoattractant. To understand the molecular mechanisms of other types of directed migration we developed a method that allows examination of cellular response to acute mechanical stimulation based on brief (2 - 5 s) exposure to shear flow. This stimulation can be delivered in a channel while imaging cells expressing fluorescently-labeled biosensors to examine individual cell behavior. Additionally, cell population can be stimulated in a plate, lysed, and immunoblotted using antibodies that recognize active versions of proteins of interest. By combining both assays, one can examine a wide array of molecules activated by changes in subcellular localization and/or phosphorylation. Using this method we determined that acute mechanical stimulation triggers activation of the chemotactic signal transduction and actin cytoskeleton networks. The ability to examine cellular responses to acute mechanical stimulation is important for understanding the initiating events necessary for shear flow-induced motility. This approach also provides a tool for studying the chemotactic signal transduction network without the confounding influence of the chemoattractant receptor.

Temporal response of chemotaxis regulators to acute mechanical stimulation
To assess the response of D. discoideum cells to mechanical stimulation, adherent aggregation-competent cells were exposed to a brief pulse of shear flow. Aggregation-competent D. discoideum cells secrete cAMP, which can be sensed by neighboring cells. To overcome the contribution of cell-cell signaling, cells were treated with caffeine, wh...

Watch this Scientific Journal Video about Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation at JoVE.com

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Here we describe methods for assessing cellular response to acute mechanical stimulation. In the microscopy-based assay, we examine localization of fluorescently-labeled biosensors following brief stimulation with shear flow. We also test activation of various proteins of interest in response to acute mechanical stimulation biochemically.

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium ...

assessment-dictyostelium-discoideum-response-to-acute-mechanical

Universidad de Cartagena UDEC

Research

JoVE Journal

Biology

6.9K Views.  SUNY Oswego. Here we describe methods for assessing cellular response to acute mechanical stimulation. In the microscopy-based assay, we examine localization of fluorescently-labeled biosensors following brief stimulation with shear flow. We also test activation of various proteins of interest in response to acute mechanical stimulation biochemically.

Video: Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Acute and Chronic Tactile Sensory Testing after Spinal Cord Injury in Rats

Spinal cord injury (SCI) impairs sensory systems causing allodynia1-8. To identify cellular and molecular causes of allodynia, sensitive and valid sensory testing in rat SCI models is needed. However, until recently, no single testing approach had been validated for SCI so that standardized methods have not been implemented across labs. Additionally, available testing methods could not be implemented acutely or when severe motor impairments existed, preventing studies of the development of SCI-induced allodynia3. Here we present two validated sensory testing methods using von Frey Hair (VFH) monofilaments which quantify changes in tactile sensory thresholds after SCI4-5. One test is the well-established Up-Down test which demonstrates high sensitivity and specificity across different SCI severities when tested chronically5. The other test is a newly-developed dorsal VFH test that can be applied acutely after SCI when allodynia develops, prior to motor recovery4-5. Each VFH monofilament applies a calibrated force when touched to the skin of the hind paw until it bends. In the up-down method, alternating VFHs of higher or lower forces are used on the plantar L5 dermatome to delineate flexor withdrawal thresholds. Successively higher forces are applied until withdrawal occurs then lower force VFHs are used until withdrawal ceases. The tactile threshold reflects the force required to elicit withdrawal in 50% of the stimuli. For the new test, each VFH is applied to the dorsal L5 dermatome of the paw while the rat is supported by the examiner. The VFH stimulation occurs in ascending order of force until at least 2 of 3 applications at a given force produces paw withdrawal. Tactile sensory threshold is the lowest force to elicit withdrawal 66% of the time. Acclimation, testing and scoring procedures are described. Aberrant trials that require a retest and typical trials are defined. Animal use was approved by Ohio State University Animal Care and Use Committee.

We describe two tactile sensory testing methods for acute or chronic periods of spinal cord injury in rats. These validated procedures can detect the development and maintenance of allodynia-like sensations.

Spinal cord injury (SCI) impairs sensory systems causing allodynia1-8. To identify cellular and molecular causes of allodynia, sensitive and valid sensory ...

Medicine

Chronic Constriction of the Sciatic Nerve and Pain Hypersensitivity Testing in Rats

Chronic neuropathic pain, resulting from damage to the central or peripheral nervous system, is a prevalent and debilitating condition, affecting 7-18% of the population1,2. Symptoms include spontaneous (tingling, burning, electric-shock like) pain, dysaesthesia, paraesthesia, allodynia (pain resulting from normally non-painful stimuli) and hyperalgesia (an increased response to painful stimuli). The sensory symptoms are co-morbid with behavioural disabilities, such as insomnia and depression. To study chronic neuropathic pain several animal models mimicking peripheral nerve injury have been developed, one of the most widely used is Bennett and Xie's (1988) unilateral sciatic nerve chronic constriction injury (CCI)3 (Figure 1). Here we present a method for performing CCI and testing pain hypersensitivity.
CCI is performed under anaesthesia, with the sciatic nerve on one side exposed by making a skin incision, and cutting through the connective tissue between the gluteus superficialis and biceps femoris muscles. Four chromic gut ligatures are tied loosely around the sciatic nerve at 1 mm intervals, to just occlude but not arrest epineural blood flow. The wound is closed with sutures in the muscle and staples in the skin. The animal is then allowed to recover from surgery for 24 hrs before pain hypersensitivity testing begins.
For behavioural testing, rats are placed into the testing apparatus and are allowed to habituate to the testing procedure. The area tested is the mid-plantar surface of the hindpaw (Figure 2), which falls within the sciatic nerve distribution. Mechanical withdrawal threshold is assessed by mechanically stimulating both injured and uninjured hindpaws using an electronic dynamic plantar von Frey aesthesiometer or manual von Frey hairs4. The mechanical withdrawal threshold is the maximum pressure exerted (in grams) that triggers paw withdrawal. For measurement of thermal withdrawal latency, first described by Hargreaves et al (1988), the hindpaw is exposed to a beam of radiant heat through a transparent glass surface using a plantar analgesia meter5,6. The withdrawal latency to the heat stimulus is recorded as the time for paw withdrawal in both injured and uninjured hindpaws. Following CCI, mechanical withdrawal threshold, as well as thermal withdrawal latency in the injured paw are both significantly reduced, compared to baseline measurements and the uninjured paw (Figure 3). The CCI model of peripheral nerve injury combined with pain hypersensitivity testing provides a model system to investigate the effectiveness of potential therapeutic agents to modify chronic neuropathic pain. In our laboratory, we utilise CCI alongside thermal and mechanical sensitivity of the hindpaws to investigate the role of neuro-immune interactions in the pathogenesis and treatment of neuropathic pain.

Due to the simplicity of surgery and the robust behavioural outcome, chronic constriction of the sciatic nerve is one of the pre-eminent animal models of neuropathic pain. Within 24 hrs following surgery, pain hypersensitivity is established and can be quantitatively measured using a von Frey aesthesiometer (mechanical test) and plantar analgesia meter (thermal test).

Chronic neuropathic pain, resulting from damage to the central or peripheral nervous system, is a prevalent and debilitating condition, affecting 7-18% of ...

Measurement of Tactile Allodynia in a Murine Model of Bacterial Prostatitis

Uropathogenic Escherichia coli (UPEC) are pathogens that play an important role in urinary tract infections and bacterial prostatitis1. We have recently shown that UPEC have an important role in the initiation of chronic pelvic pain2, a feature of Chronic prostatitis/Chronic pelvic pain syndrome (CP/CPPS)3,4. Infection of the prostate by clinically relevant UPEC can initiate and establish chronic pain through mechanisms that may involve tissue damage and the initiation of mechanisms of autoimmunity5.
A challenge to understanding the pathogenesis of UPEC in the prostate is the relative inaccessibility of the prostate gland to manipulation. We utilized a previously described intraurethral infection method6 to deliver a clinical strain of UPEC into male mice thereby establishing an ascending infection of the prostate. Here, we describe our protocols for standardizing the bacterial inoculum7 as well as the procedure for catheterizing anesthetized male mice for instillation of bacteria.
CP/CPPS is primarily characterized by the presence of tactile allodynia4. Behavior testing was based on the concept of cutaneous hyperalgesia resulting from referred visceral pain8-10. An irritable focus in visceral tissues reduces cutaneous pain thresholds allowing for an exaggerated response to normally non-painful stimuli (allodynia). Application of normal force to the skin result in abnormal responses that tend to increase with the intensity of the underlying visceral pain. We describe methodology in NOD/ShiLtJ mice that utilize von Frey fibers to quantify tactile allodynia over time in response to a single infection with UPEC bacteria.

Infection of the prostate may be a contributing factor in mediating pelvic pain in chronic prostatitis. We describe the procedure for preparation of standardized bacterial inoculum, instillation of bacteria into the urethra of male mice and methodology for measuring tactile allodynia in mice over time.

Uropathogenic Escherichia coli (UPEC) are pathogens that play an important role in urinary tract infections and bacterial prostatitis1. We have recently ...

Immunology and Infection

Local and Global Methods of Assessing Thermal Nociception in Drosophila Larvae

In this article, we demonstrate assays to study thermal nociception in Drosophila larvae. One assay involves spatially-restricted (local) stimulation of thermal nociceptors1,2 while the second involves a wholesale (global) activation of most or all such neurons3. Together, these techniques allow visualization and quantification of the behavioral functions of Drosophila nociceptive sensory neurons.
The Drosophila larva is an established model system to study thermal nociception, a sensory response to potentially harmful temperatures that is evolutionarily conserved across species1,2. The advantages of Drosophila for such studies are the relative simplicity of its nervous system and the sophistication of the genetic techniques that can be used to dissect the molecular basis of the underlying biology4-6 In Drosophila, as in all metazoans, the response to noxious thermal stimuli generally involves a "nocifensive" aversive withdrawal to the presented stimulus7. Such stimuli are detected through free nerve endings or nociceptors and the amplitude of the organismal response depends on the number of nociceptors receiving the noxious stimulus8. In Drosophila, it is the class IV dendritic arborization sensory neurons that detect noxious thermal and mechanical stimuli9 in addition to their recently discovered role as photoreceptors10. These neurons, which have been very well studied at the developmental level, arborize over the barrier epidermal sheet and make contacts with nearly all epidermal cells11,12. The single axon of each class IV neuron projects into the ventral nerve cord of the central nervous system11 where they may connect to second-order neurons that project to the brain.
Under baseline conditions, nociceptive sensory neurons will not fire until a relatively high threshold is reached. The assays described here allow the investigator to quantify baseline behavioral responses or, presumably, the sensitization that ensues following tissue damage. Each assay provokes distinct but related locomotory behavioral responses to noxious thermal stimuli and permits the researcher to visualize and quantify various aspects of thermal nociception in Drosophila larvae. The assays can be applied to larvae of desired genotypes or to larvae raised under different environmental conditions that might impact nociception. Since thermal nociception is conserved across species, the findings gleaned from genetic dissection in Drosophila will likely inform our understanding of thermal nociception in other species, including vertebrates.

Local and Global Methods of Assessing Thermal Nociception in Drosophila Larvae

In this article, we demonstrate assays to study thermal nociception in Drosophila larvae. One assay involves spatially-restricted (local) stimulation of thermal nociceptors1,2 while the second involves a wholesale (global) activation of most or all such neurons3. Together, these techniques allow visualization and quantification of the behavioral functions of Drosophila nociceptive sensory neurons.

In this article, we demonstrate assays to study thermal nociception in Drosophila larvae. One assay involves spatially-restricted (local) stimulation of ...

Neuroscience

Measuring Changes in Tactile Sensitivity in the Hind Paw of Mice Using an Electronic von Frey Apparatus

Measuring inflammation-induced changes in thresholds of hind paw withdrawal from mechanical pressure is a useful technique to assess changes in pain perception in rodents. Withdrawal thresholds can be measured first at baseline and then following drug, venom, injury, allergen,&#160;or otherwise evoked inflammation by applying an accurate force on very specific areas of the skin. An electronic von Frey apparatus allows precise assessment of mouse hind paw withdrawal thresholds that are not limited by the available filament sizes in contrast to classical von Frey measurements. The ease and rapidity of measurements allow for incorporation of assessment of tactile sensitivity outcomes in diverse models of rapid-onset inflammatory and neuropathic pain as multiple measurements can be taken within a short time period. Experimental measurements for individual rodent subjects can be internally controlled against individual baseline responses and exclusion criteria easily established to standardize baseline responses within and across experimental groups. Thus, measurements using an electronic von Frey apparatus represent a useful modification of the well-established classical von Frey filament-based assays for rodent mechanical allodynia that may also be applied to other nonhuman mammalian models.

Electronic von Frey measurements are an effective and improved alternative to classical von Frey filaments, as they allow rapid and precise measurement of changes in rodent mechanical withdrawal thresholds to continuously applied pressure stimuli before and after an inflammatory event.

Measuring inflammation-induced changes in thresholds of hind paw withdrawal from mechanical pressure is a useful technique to assess changes in pain ...

An Improved Assay and Tools for Measuring Mechanical Nociception in Drosophila Larvae

Published assays for mechanical nociception in Drosophila have led to variable assessments of behavior. Here, we fabricated, for use with Drosophila larvae, customized metal nickel-titanium alloy (nitinol) filaments. These mechanical probes are similar to the von Frey filaments used in vertebrates to measure mechanical nociception. Here, we demonstrate how to make and calibrate these mechanical probes and how to generate a full behavioral dose-response from subthreshold (innocuous or non-noxious range) to suprathreshold (low to high noxious range) stimuli. To demonstrate the utility of the probes, we investigated tissue damage-induced hypersensitivity in Drosophila larvae. Mechanical allodynia (hypersensitivity to a normally innocuous mechanical stimulus) and hyperalgesia (exaggerated responsiveness to a noxious mechanical stimulus) have not yet been established in Drosophila larvae. Using mechanical probes that are normally innocuous or probes that typically elicit an aversive behavior, we found that Drosophila larvae develop mechanical hypersensitization (both allodynia and hyperalgesia) after tissue damage. Thus, the mechanical probes and assay that we illustrate here will likely be important tools to dissect the fundamental molecular/genetic mechanisms of mechanical hypersensitivity.

An Improved Assay and Tools for Measuring Mechanical Nociception in Drosophila Larvae

The goal of this protocol is to show how to perform an improved assay for mechanical nociception in Drosophila larvae. We use the assay here to demonstrate that mechanical hypersensitivity (allodynia and hyperalgesia) exists in Drosophila larvae.

Published assays for mechanical nociception in Drosophila have led to variable assessments of behavior. Here, we fabricated, for use with Drosophila ...

Behavior

In vitro Functional Characterization of Mouse Colorectal Afferent Endings

This video demonstrates in detail an in vitro single-fiber electrophysiological recording protocol using a mouse colorectum-nerve preparation. The approach allows unbiased identification and functional characterization of individual colorectal afferents. Extracellular recordings of propagated action potentials (APs) that originate from one or a few afferent (i.e., single-fiber) receptive fields (RFs) in the colorectum are made from teased nerve fiber fascicles. The colorectum is removed with either the pelvic (PN) or lumbar splanchnic (LSN) nerve attached and opened longitudinally. The tissue is placed in a recording chamber, pinned flat and perfused with oxygenated Krebs solution. Focal electrical stimulation is used to locate the colorectal afferent endings, which are further tested by three distinct mechanical stimuli (blunt probing, mucosal stroking and circumferential stretch) to functionally categorize the afferents into five mechanosensitive classes. Endings responding to none of these mechanical stimuli are categorized as mechanically-insensitive afferents (MIAs). Both mechanosensitive and MIAs can be assessed for sensitization (i.e., enhanced response, reduced threshold, and/or acquisition of mechanosensitivity) by localized exposure of RFs to chemicals (e.g., inflammatory soup (IS), capsaicin, adenosine triphosphate (ATP)). We describe the equipment and colorectum&#8211;nerve recording preparation, harvest of colorectum with attached PN or LSN, identification of RFs in the colorectum, single-fiber recording from nerve fascicles, and localized application of chemicals to the RF. In addition, challenges of the preparation and application of standardized mechanical stimulation are also discussed.

In vitro Functional Characterization of Mouse Colorectal Afferent Endings

This video demonstrates a protocol for conducting single-fiber electrophysiological recordings on an in vitro mouse colorectum-nerve preparation.

This video demonstrates in detail an in vitro single-fiber electrophysiological recording protocol using a mouse colorectum-nerve preparation. The ...

Assessment of Perigenital Sensitivity and Prostatic Mast Cell Activation in a Mouse Model of Neonatal Maternal Separation

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) has a lifetime prevalence of 14% and is the most common urological diagnosis for men under the age of 50, yet it is the least understood and studied chronic pelvic pain disorder. A significant subset of patients with chronic pelvic pain report having experienced early life stress or abuse, which can markedly affect the functioning and regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Mast cell activation, which has been shown to be increased in both urine and expressed prostatic secretions of CP/CPPS patients, is partially regulated by downstream activation of the HPA axis. Neonatal maternal separation (NMS) has been used for over two decades to study the outcomes of early life stress in rodent models, including changes in the HPA axis and visceral sensitivity. Here we provide a detailed protocol for using NMS as a preclinical model of CP/CPPS in male C57BL/6 mice. We describe the methodology for performing NMS, assessing perigenital mechanical allodynia, and histological evidence of mast cell activation. We also provide evidence that early psychological stress can have long-lasting effects on the male urogenital system in mice.

We are measuring perigenital mechanical sensitivity and mast cell activation in the prostate of male C57BL/6 mice that underwent an early life stress paradigm &#8211; neonatal maternal separation, in order to induce a preclinical model of chronic prostatitis/chronic pelvic pain syndrome.

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) has a lifetime prevalence of 14% and is the most common urological diagnosis for men under the ...

Novel Assay for Cold Nociception in Drosophila Larvae

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory machinery, such as in patients experiencing peripheral neuropathy or injury-induced sensitization, are not well characterized. The genetically tractable Drosophila model has been used to study the cells and genes required for noxious heat detection, which has yielded multiple conserved genes of interest. Little is known however about the cells and receptors important for noxious cold sensing. Although, Drosophila does not survive prolonged exposure to cold temperatures (&#8804;10 &#186;C), and will avoid cool, preferring warmer temperatures in behavioral preference assays, how they sense and possibly avoid noxious cold stimuli has only recently been investigated.
Here we describe and characterize the first noxious cold (&#8804;10 &#186;C) behavioral assay in Drosophila. Using this tool and assay, we show an investigator how to qualitatively and quantitatively assess cold nociceptive behaviors. This can be done under normal/healthy culture conditions, or presumably in the context of disease, injury or sensitization. Further, this assay can be applied to larvae selected for desired genotypes, which might impact thermosensation, pain, or nociceptive sensitization. Given that pain is a highly conserved process, using this assay to further study&#160;thermal nociception will likely glean important understanding of pain processes in other species, including vertebrates.

Novel Assay for Cold Nociception in Drosophila Larvae

Here we demonstrate a novel assay to study cold nociception in Drosophila larvae. This assay utilizes a custom-built Peltier probe capable of applying a focal noxious cold stimulus and results in quantifiable cold-specific behaviors. This technique will allow further cellular and molecular dissection of cold nociception.

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory ...

Implantation of Osmotic Pumps and Induction of Stress to Establish a Symptomatic, Pharmacological Mouse Model for DYT/PARK-ATP1A3 Dystonia

Genetically modified mouse models face limitations, especially when studying movement disorders, where most of the available transgenic rodent models do not present a motor phenotype resembling the clinical aspects of the human disease. Pharmacological mouse models allow for a more direct study of the pathomechanisms and their effect on the behavioral phenotype. Osmotic pumps connected to brain cannulas open up the possibility of creating pharmacological mouse models via local and chronic drug delivery. For the hereditary movement disorder of rapid-onset dystonia-parkinsonism, the loss-of-function mutation in the &#945;3-subunit of the Na+/K+-ATPase can be simulated by a highly specific blockade via the glycoside ouabain. In order to locally block the &#945;3-subunit in the basal ganglia and the cerebellum, which are the two brain structures believed to be heavily involved in the pathogenesis of rapid-onset dystonia-parkinsonism, a bilateral cannula is stereotaxically implanted into the striatum and an additional single cannula is introduced into the cerebellum. The cannulas are connected via vinyl tubing to two osmotic pumps, which are subcutaneously implanted on the back of the animals and allow for the chronic and precise delivery of ouabain. The pharmacological mouse model for rapid-onset dystonia-parkinsonism carries the additional advantage of recapitulating the clinical and pathological features of asymptomatic and symptomatic mutation carriers. Just like mutation carriers of rapid-onset dystonia parkinsonism, the ouabain-perfused mice develop dystonia-like movements only after additional exposure to stress. We demonstrate a mild stress paradigm and introduce two modified scoring systems for the assessment of a motor phenotype.

We provide a protocol to generate a pharmacological DYT/PARK-ATP1A3 dystonia mouse model via implantation of cannulas into basal ganglia and cerebellum connected to osmotic pumps. We describe the induction of dystonia-like movements via application of a motor challenge and the characterization of the phenotype via behavioral scoring systems.

Genetically modified mouse models face limitations, especially when studying movement disorders, where most of the available transgenic rodent models do ...

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

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Novel Assay for Cold Nociception in Drosophila Larvae

Implantation of Osmotic Pumps and Induction of Stress to Establish a Symptomatic, Pharmacological Mouse Model for DYT/PARK-ATP1A3 Dystonia