Threshold temperature responses of thermosensitive neurons in guinea-pig hypothalamic slices

1. 1.|Neuronal activity in slices of the preoptic and anterior hypothalamic area of guinea-pigs during slow low-amplitude temperature changes analogous to temperature changes in the brain of endothermic animals, was extracellularly recorded. 2. 2.|42% of neurons showed threshold temperature responses. The threshold of response averaged 37.4°C for warm-sensitive neurons during warming and 37.0°C for cold-sensitive neurons during cooling. 3. 3.|The thresholds differed, on average, by 0.1°C in the same neuron at repeated temperature changes. 4. 4.|With temperatures 0.8°C above threshold on average (0.2°C in some units) neuronal activity reached a new high level that did not change either during a further exceeding of the threshold or prolonged maintenance of suprathreshold temperature. 5. 5.|The characteristics of the threshold temperature response of a hypothalamic neuron meet the criteria of thermoinduced structural rearrangements of cell membranes, caused by phase transitions of lipids, changes in protein conformation and cytoskeletal activity.