Temperature-related nerve function in warm- and cold-climate muskrats.

MILLER, L. KEITH., AND LAURENCE IRVING. Temperaturerelated nerve function in warmand cold-climate muskrats. Am. J. Physiol. 213(5): 1295-1298. 1967.-The bare extremities of the semiaquatic muskrat exhibit large temperature fluctuations in response to varying thermal conditions of the animal or its environment. Tissues of these heterothermous extremities, including nerves, must remain operational over a wide temperature range in order to maintain the functional integrity of the living animal. Functional characteristics in relation to temperature were studied in excised caudal nerves of muskrats from Alaska and Louisiana. Nerves from both groups conducted well-formed action potentials even when supercooled. The cold-accustomed Alaska muskrat nerves differed from their Louisiana counterparts with respect to conduction velocity and excitability characteristics. At temperatures above 5 C conduction velocity was higher in nerves of animals from the warmer climate. This difference increased with increasing temperature. At 15 C or below, the excitability of Louisiana muskrat caudal nerves to stimuli of short duration was significantly less than in nerves accustomed to cold. The findings provide further evidence for differences in nerve function in animals exposed to different environmental temperatures.