Thermal stimulation of electrical activity of single units of the preoptic region

Abstract

Single unit activity has been recorded in the hypothalamus and preoptic region of cats anesthetized with urethan during local hypothalamic heating and cooling. Heating was accomplished by radio frequency current (3.7 megacycles/sec) and heating and cooling by circulating warm and cold water through small steel thermodes placed 4–6 mm on each side of the midline. Local tissue temperature was recorded by thermocouples and by thermistors. It was observed from a study of about 1,000 neurons that a) about one neuron in five increased its rate of spontaneous discharge with increase in local temperature from 32 to 41 C (Q₁₀ = 5–15); b) 80% of the units did not respond to temperature change by changing their spontaneous discharge rate in the 34–41 C temperature range; c) thermally sensitive neurons were found only in the midline region immediately rostroventral to the anterior commissure; d) no units were found for which the discharge frequency increased by decreasing the local temperature.