Responses of Midbrain raphe neurons to local temperature

The effect of heating and cooling in the midbrain on the unit activities of midbrain raphe neurons in the rat was observed. Out of 24 raphe units studied, 14 units responded to a rise in midbrain temperature with an increased rate of firing. The remaining 10 units did not respond to temperature changes between 34 and 41 degrees C. The result is consistent with the idea that the heat-induced increase in brain serotonin turnover is mediated by an increased firing rate of midbrain raphe neurons.