EXAMINATION OF THE STRATEGIES RATS USE TO WITHDRAW FROM MECHANICAL STIMULATION OF THE LEG

The strategy by which mammals withdraw from threatening and potentially painful stimuli is unclear. Over the summer, my colleagues and I delivered heat stimuli to the bottom surface of the rat hind foot to evoke a nociceptive withdrawal response and found that the direction of response depended more on the initial position of the foot prior to stimulation than on stimulus location. The specific aim of my current research is to test the hypothesis that initial foot location rather than stimulus location determines withdrawal response direction now using a mechanical stimulus. Rats were stimulated by pressing nylon monofilaments of varying diameters into five different locations on the bottom of the rat’s foot to induce a rapid upward nociceptive withdrawal response followed within 100ms by replacement of the foot on the surface. The responses were recorded by video (60 fps) and analyzed to measure the initial position of the foot and the final position after stimulation, thus defining the response as a vector with direction and magnitude. In preliminary analysis, a two-way analysis of variance revealed that stimulus location did not influence response direction. In contrast, linear regression showed that, similar to the responses to heat stimuli, the response direction depended on initial location of the paw. Together, these two studies reveal a general strategy by which rats withdraw from aversive stimuli. Uncovering the strategies by which mammals deal with potentially painful and tissue damaging stimuli could provide valuable insight into both normal sensorimotor integration and the mechanisms underlying neurological disorders.

Additional Abstract Information

Student(s): Taylor L. Berrena, Miriam Kabore, Giavanna Verdi

Department: Biology

Faculty Advisor: Dr. Corey Cleland

Type: Poster

Year: 2015