Olfactory Assays for Mouse Models of Neurodegenerative Disease

The overall goal of this procedure is to assess the olfactory function in mice. This is accomplished by first putting the mice on food restriction or individual housing. The second step is to prepare the olfactory stimuli, setting up the testing room and habituate the mice to the testing area so that the tests can be performed.

Next, conduct the testing procedures on the mice and analyze the data that was recorded on the video. Ultimately, these tests can be used to measure the olfactory abilities in genetic mouse models of neurodegenerative disease and in clinical drug studies to test potential therapies. Although olfactory deficits are well-documented in neurodegenerative diseases, olfaction is not routinely measured in many disease models.

Therefore, our goal is to assemble a battery of tests to measure multiple aspects of olfaction and mice that can be easily implemented into an experiment. These tests can help answer key questions related to the relationship between neurodegenerative disease, pathology, and olfaction, as well as to help identify the therapeutic potential of novel compounds. To begin this procedure, give the mouse one to two pellets to be used during the test daily.

Then at least two days before testing, record the weight of the mouse and then food restricted to 90%of its body weight on all the test days. Habituate the mouse for one hour prior to testing by placing the home cage in the testing room with just a filter top lid. During habitation, fill a clean cage with clean bedding to three centimeters high and make sure that the bedding is evenly distributed throughout the cage.

Bury one sweetened cereal pellet 0.5 centimeters below the bedding in the test cage so that it's not visible. After that, transfer the mouse from its home cage to the test cage and placed a filter top lid on the cage. Start counting down five minutes with a timer.

Stop the timer when the mouse uncovers the pellet and begins eating it. If the mouse does not find the pellet within five minutes, end the trial and record a score of 300 seconds for that mouse. Move the pellet to the top of the bedding to allow the mouse to eat it.

Following the trial, return the mouse to his home cage. Now empty the bedding from the test cage and clean the cage with cleaning solution. Repeat the procedure for each mouse and change gloves before and after each mouse.

Then give the mouse just enough food to maintain 90%body weight. Perform the testing on day two to five the same way as test day one, but bury the pellet in a different spot in the cage for each trial on testing. Day six, instead of bearing the pellet under the bedding, place it on top of the bedding.

Record the time for the mouse to find and start eating the pellet in this step. Place five blocks labeled A through E in the clean mouse home cage for 24 hours. On the next day and one hour prior to testing, remove the water bottle and feeder bin and transfer all five blocks from the cage along with a handful of bedding into a plastic bag labeled with the animal's identification.

Then habituate the animal in its home cage without the water bottle feeder bin, and blocks for one hour prior to testing. Now, line up all the mouse cages on a table with at least 10 centimeters between cages. Then label the card with the important experiment details and videotape the label for two to three seconds.

Remove blocks A through D from the plastic bag with that mouse's identification, and place them in the middle of the cage so that they're clearly visible on the video camera. Make sure that there is about one centimeter of space between the blocks. Now place the filter top back on the cage.

Start the timer and videotape for 30 seconds. After 30 seconds, stop the recording. Remove the blocks from the cage and place them outside of the cage between trials.

Change gloves and then move on to the next mouse. Do this for a total of six trials for each mouse, making sure there is an inter trial interval of about five minutes. On the seventh trial, remove block D from its own cage and add block E from another mouse's cage.

So if the mouse is exposed to block A, B, and C from its own home cage and block E from another mouse's cage record in the lab book whose block E each mouse is exposed to and the alternate placement of block E.In each mouse's cage, videotape for 30 seconds. Following the seven trials, return the animal to a new clean gauge with its original cage mates. Clean the blocks used in the test with mild detergent and water and allow them to air dry for use In later tests, perform the habituation dis habituation test in a similar manner as the block test.

But instead of using blocks that have the odor of a mouse, use tissue cartridges holding cotton scented with different pairs of extracts. Then habituate the mouse in the test room. Prepare the scented tissue cartridges in a separate room.

Place a small cotton ball in a clean cartridge, and then add five microliters of extract to the cotton. Snap the cartridge top over the cotton and place in a dedicated box or bag labeled with that scent. Change gloves between handling scents.

Then follow the procedures in the block test using 1 cent, a tissue cartridge for the first six trials and the second cent a tissue cartridge for the seventh trial. This figure shows the latency to find the pellet in the wild type and the A TP 13 A two knockout mice in the buried pellet test. This figure shows the time sniffing the novel block block E in the block test between the wild type and the ATP 13 A two knockout mice.

And this is the meantime sniffing assented cartridge in wild type mice across six trials and the introduction of a cartridge with the novel scent on trial seven in the habituation dis habituation test. While performing this battery of tests, it's important to remember to take all measures to reduce any outside olfactory cues. Always change your gloves as often as possible, and avoid wearing any perfume or cologne.

After watching this video, you should have good understanding of how to assess olfactory function and mouse models of neurodegenerative disease using this battery of straightforward tests.