The overall goal of this procedure is to study motivated behavior in mice by training them to perform an operant response for a sensory reinforcer. This is accomplished by writing a program to deliver variable sensory stimuli. When the animal performs an operant task, it is very important that the animals are kept calm during handling, so the experimenter must habituate the mice prior to testing.
Once the mice are habituated, the next step is to perform daily operant test sessions on a fixed ratio of one schedule. Finally, the schedule of reinforcement can be advanced to a different schedule, such as progressive ratio, random ratio, or variable interval ratio testing. Scheme operant sensation seeking can be used to show changes in operant responding as a result of a genetic or pharmacological manipulation.
The main advantage of this technique over existing methods, such as intravenous drug self-administration in the mouse, is that no surgery training or food restriction is required. In addition to providing insight into motivated behavior. Operant sensation seeking can also be applied to systems such as drug addiction.
Before the experiment can begin, animals must first be habituated to the handling and transportation. They will experience habitation takes place over a three day period. After the mice have acclimated to the animal facility on the first day of habituation, place gloved hands into the cage and let them sit for 90 seconds.
If every mouse has not investigated your hands in that time, gently move hands towards each mouse and wait for them to sniff and or contact your hands before proceeding. Next carefully pick up each mouse by the base of the tail and place it on your hand. Quickly lift your hand up and bring it back down to allow the mouse to walk off it and back into the cage.
Repeat this maneuver for each mouse. Depending on their demeanor, five to 10 repetitions may be needed until the mouse remains calm. The final time, raise your hand higher and hold the mouse for five seconds.
The mouse must stay on the hand the entire time in order to meet the criteria for the day. Repeat this procedure for each cage, changing gloves between cages on the first day of habituation. Return to the facility on the following day to complete the second round of habitation.
Handle each mouse as on the previous day by placing them on your hand and allowing them to walk back into the cage. The final lift should be held for 10 seconds. Next, place the animal in your hand and stroke.
Its back. Also, starting on day two, weigh each animal and mark their tail with a sharpie to denote subject number On the third day of habituation, repeat the steps demonstrated on days one and two, holding the animal high in the hand for 15 seconds. For the final lift, weigh each mouse and remark their tails.
After all mice have met their criteria for the day, they are habituated and ready for testing. You will first need to write the program that will be used for opera sensation seeking or OSS program. Fixed ratio or FR sessions lasting for one hour.
Progressive ratio or PR sessions should be programmed to last for two. Extend both levers and counterbalance them for which lever is designated active versus inactive across animals. The lever assignment for each animal never changes.
Code the program so that the auditory and visual reinforcers are varied. The duration of each is chosen randomly and last either 2, 4, 6, or eight seconds. The lamp flash rates are also chosen randomly and vary between 0.6 2 5, 1 0.25, 2.5, or five hertz each with a 50%duty cycle.
The stimulus lamp flashes vary between the left and right side of the chamber. Next program an auditory stimulus for the duration of the reinforcer. Here, an infusion pump provides sound approximately three decibels above the background noise in the chamber.
Make sure the chamber is clean and working properly before starting the experiment. First, wash the bottom pan with hot water. Next, clean the operant chamber, walls, and floors with 30%ethanol.
Run a test program that turns on the fan and house and stimulus lights, as well as extends and records lever presses. Once it is determined that all lights and fans are operating correctly, test the program to ensure that all lever presses are recorded. Finally, clean levers with 30%ethanol opera sessions should be conducted for five to six days a week at the same time each day.
In this example, experiments are typically conducted between oh 800 and 1400 hours. During the dark phase of the animal's light cycle, weigh each mouse. Before testing, load the program for each chamber and annotate the experiment appropriately.
Transport each mouse into its designated chamber, close the door and start the session. After the session ends, promptly remove the mouse and remark the tail. Clean chambers as demonstrated earlier, analyze data for the number of active and inactive lever presses.
The number of reinforcers and or lever accuracy can also be reported. All mice must meet the acquisition criteria if they're to be tested for the effect of a treatment on OSS greater than 20 active lever presses and greater than 65%active lever presses for the final three fixed ratio sessions should be obtained prior to beginning treatment. After the acquisition of FR one responding, the schedule of reinforcement can be changed.
For example, a higher fixed ratio, progressive ratio or random ratio. Here we see an example of the acquisition of operant sensation seeking behavior. In male C 57, black six J mice, OSS mice received varied visual and auditory stimuli following each active lever.Press.
While inactive lever presses had no consequence control, mice underwent identical conditions, except that there was no consequence for pressing either lever. With each successive session, active lever pressing by OSS mice was increased relative to inactive lever. Pressing control.
Mice represented by the gray lines failed to show this increase. In this example, one group of mice received OSS reinforcement. While another group received 10%ensure as food reinforcement when allowed ad Liam access to food response rates for OSS and food reinforcement increased similarly over time.
In the next example, mice were advanced to a progressive ratio schedule of reinforcement for five days. The data here represent the means of values from days four and five for each animal. The final ratio completed is reported on the Y axis to the right and refers to the number of responses required to obtain the corresponding reinforcer as was demonstrated for fixed ratio responding.
Progressive ratio. Responding rates were similar between OSS and food reinforcers. Using this method, the effect of a manipulation on two different reinforcement types, sensory and food can be compared without the potential confounds resulting from hunger state or differences in response rate.
In conclusion, operant sensation seeking behavior provides a unique tool to study the molecular mechanisms underlying sensory reinforcement, and may additionally provide a tool to study drug addiction.
