Static an dynamic activity of cold receptors in cats after long-term exposure to various temperatures

Ten cats were adapted for 4.7 years in a climatic chamber to an ambient temperature of 5 degree C an 8 cats to 30 degree C under artificial illumination and food ad libitum., Cats living at 5 degree C had 15.2 +/- 0.5 mean nasal and 38.0 +/- 0.3 degree C mean rectal temperature; the corresponding values for cats living at 30 degree C were 31.0 +/- 0.4 degree an 38.3 +/- 0.1 degree C. Static and dynamic activities of single specific cold fibers from the nose were recorded when applying static temperature of 40, 35, 30, 25, 20, 15 and 10 degree C and dynamic cooling steps of 5 degree C starting from static temperature between 40 and 15 degree C. In each group, a population of 100 cold fibers was examined. The average static frequencies between 35 and 20 degree C slightly but not significantly lower in the cold adapted group, the respective values for both groups at 30 degree C being 5.6 and 5.6s-1. The average dynamic maxima were considerably lower in the cold adapted group throughout the whole temperature range, the values at 30 degree C being 44 and 61s-1, respectively. The difference between the dynamic frequency-temperature curves of both fiber populations was highly significant (P less than 0.001). The distribution of static maxima of individual cold fibers as well as the distribution of fibers with static bursts was nearly identical for both groups, whereas the distribution of dynamic maxima and dynamic bursts was significantly shifted lower temperatures in the could adapted group. Seven sub-groups of cold fibers were formed according to their static maximum at temperatures between 40 and 10 degree C. The most pronounced adaptive modification was a significantly lower dynamic peak frequency of the sub-groups with static maxima at 15, 20, 25, 35 and 40 degree C in the cold adapted animals.