Static and dynamic activity of cold receptors in cats after long-term exposure to various temperatures
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Ten cats were adapted for 4.7 years in a climatic chamber to an ambient temperature of 5°C and 8 cats to 30°C under artificial illumination and food ad libitum. Cats living at 5°C had 15.2±0.5 mean nasal and 38.0±0.3°C mean rectal temperature; the corresponding values for cats living at 30°C were 31.0±0.4°C and 38.3±0.1°C.
Static and dynamic activities of single specific cold fibers from the nose were recorded when applying static temperatures of 40, 35, 30, 25, 20, 15 and 10°C and dynamic cooling steps of 5°C starting from static temperatures between 40 and 15°C. In each group, a population of 100 cold fibers was examined.
The average static frequencies between 35 and 20°C were slightly but not significantly lower in the cold adapted group, the respective values for both groups at 30°C being 5.6 and 6.5s−1. The average dynamic maxima were considerably lower in the cold adapted group throughout the whole temperature range, the values at 30°C being 44 and 61s−1, respectively. The difference between the dynamic frequency-temperature curves of both fiber populations was highly significant (P<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 to lower temperatures in the cold adapted group.
Seven sub-groups of cold fibers were formed according to their static maximum at temperatures between 40 and 10°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°C in the cold adapted animals.
Key wordsCold receptors Long-term thermal adaptation Static discharge Dynamic discharge Burst discharge
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