The overall aim of this procedure is to monitor circadian rhythms of running wheel activity in rodents. This is accomplished by first assembling the appropriate hardware. Next specialized software is configured to record the running activity.
Over time, the recorded data is converted into ACTO grams and periodo grams for analysis. Ultimately, the continuous monitoring of running wheel activity is used to study the influence of genetic, pharmacological and environmental factors on the circadian clock in rodents. Hi, I'm Dr.Michael Ver.
The implications of this technique extend towards the diagnosis and therapy of many psychiatric conditions because conditions such as schizophrenia or bipolar disorder are both accompanied by disrupted circadian rhythms and sleep. Generally, individuals new to this technique will struggle with a lack of appropriate hardware or software, as well as a general misunderstanding of what these data can demonstrate. Begin by setting up the home cage.
Each rodent should be singly housed with enough room for a running wheel. Cages with mesh flooring are used to eliminate any possible neophobic effects of frequent bedding changes. Smaller, lighter wheels are used for mice, while larger, heavier wheels are used for rats.
Each cage is placed inside a sound attenuated isolation box. Multiple cages can be housed together, however, cages housed singly avoid possible interference from surrounding odors to allow for adequate ventilation. Each box should be equipped with a fan that is hooded to prevent light from entering small light.
Tight vents allow air to enter the isolation boxes from several points and to help control airflow. A single light source should be installed at a similar location above each cage for consistent lighting between isolation boxes. For studies that require the animals to remain in darkness, the room is illuminated with dim red light first.
Set up the running wheel that will be used in the study. Confirm that the wheel can spin freely and does not wobble. Each running wheel should be equipped with a micro switch that records every revolution.
This information travels to QA four modules and is then relayed to the DP 24 data port and is finally recorded by a vital view equipped computer. Next, load the software that will record the data here. Vital viewers use to collect data from many single channel sources into a single computer file once everything is set up properly.
Begin the study by placing the rodent of choice in their home cage. The animals will running activity will then be recorded over time after a set time period. Specifically designed programs convert the data into ACTO grams, which illustrate the daily pattern of activity over time, and periodo grams, which perform a spectral analysis of the rhythm and calculate the strongest period.
In this example, animals were housed under a standard light dark cycle. Under these conditions, this rat became active at the same time each day, showing an exact 24 hour peak in the periodo gram. This example shows the behavior of a rat that was housed in constant darkness.
Under these conditions, the rat was active slightly later each day. Hence, the right would drift in the Acto gram and 24.33 hour peak in the periodo gram. The free running period can also be calculated manually.
First, draw a line at the onset of daily activity. Next, calculate the slope in hours per day, and finally, add 24 hours. Here arrhythmic patterns of running wheel activity are seen in rats with lesions of the supra charismatic nucleus housed under constant darkness.
The rat fail to show an endogenous circadian rhythm in running wheel activity. The Periodo Graham on the right confirms that there is no significant rhythm in the circadian range. Lighting conditions have strong effects on the patterns of running wheel activity.
Here the rat is initially housed under constant darkness as denoted by the shaded portion. Under this condition, peak activity is found at 24.33 hours. Next, the rat is housed under constant light shown here.
Under this condition, the endogenous circadian clock is disrupted gradually over two to three weeks, and the rat becomes a rhythmic towards the bottom of this portion of the Acto gram. Finally, the normal 12 hour, 12 hour light dark cycle was reinstated and the rhythm was restored After its development. This technique paved the way for researchers studying circadian rhythms to explore the properties of the circadian clock in rodents and after watching this video, you should have a good understanding of how to measure and analyze these rhythms.
