Thermosensitive characteristics of a preoptic area neuron recorded over a 20 day period in the rabbit

The thermosensitive characteristics of a single preoptic area neuron were monitored over a period of twenty days from a rabbit fitted with chronic recording electrodes. No demonstrable daily changes were detected in either the basal firing rate or the mean interspike interval during control recordings. Only minor daily variations were observed in thermosensitivity (impulses-second/degree C) and in the interspike interval coefficient of variation for this neuron in response to preoptic heating and cooling with a water-perfused thermode. When measured during early morning, early afternoon and at late night, thermosensitivity remained constant and showed no apparent circadian rhythm. The results from this single thermosensitive preoptic area neuron suggest that in spite of circadian rhythms of body temperature and other physiological parameters, some thermoregulatory neurons retain fixed temperature sensitive properties under conditions of stable ambient temperature.