Central short-term cold adaptation in the guinea-pig

The responses of seventeen single units to changes in skin temperature were recorded in fifteen guinea-pigs anaesthetized with urethane. All units were located in the subcoeruleus region which has been discussed as part of the thermoafferent system. Thermal stimuli were applied to different skin areas. The receptive fields of sixteen cold-responsive units were found to be parts of the abdominal and thoracic skin. The cold-responsive units could be subdivided into two groups. Ten units showed the known classic cold-responsive steady state response. A short-term thermal adaptation was seen in six units. These units had peak activities at skin temperatures between 22 degrees C and 29 degrees C and decreased their firing rates within 5 to 40 minutes when the temperature of the receptive skin area was kept constant in the range between 20 degrees C and 29 degrees C. This short-term cold-adaptive effect could be reversibly abolished by warming the corresponding skin area for a certain period of time. The short-term adapting neurones could be conceived of as the neurophysiological correlate to cold-adaptive changes in thermogenic responses seen in three guinea-pigs. Oxygen uptake and shivering activity were reduced in animals, which had reached approximately constant skin and core body temperature during sustained external cooling.