Characteristics of thermosensitive neurons of the posterior hypothalamus.

Changes in the firing rate of 260 posterior hypothalamic neurons were investigated in experiments on unanesthetized rabbits. In the animals in the initial state the temperature of the posterior hypothalamus was 39.1 +/- 0.02 degrees C, the temperature of the nasal spine was 33.0 +/- 0.02 degrees C, and the skin temperature on the concha auriculae was 30.1 +/- 0.3 degrees C, values which correspond on the whole to those in the thermoneutral zone for the rabbit. During a local increase (by 0.6-1.5 degrees C) or decrease (by 0.6-2 degrees C) in temperature of this region of the brain about 28% of responding neurons were found; most of them changed their firing rate when the brain temperature reached a certain level for each neuron. The threshold varied from 0.6 to 1.0 degrees C from the level of the brain temperature in the thermoneutral zone.