Dynamic response of preoptic and hypothalamic neurons to scrotal thermal stimulation in rats

Activities of preoptic and anterior hypothalamic (POAH) neurons were recorded in anesthetized rats in response to scrotal thermal stimulation. Thirteen out of 54 neurons responsive to changes of scrotal temperature (Tscr) showed dynamic responses. Four of these neurons increased and 3 neurons decreased their firing rates responding dynamically to warming but not to cooling. Six other neurons were inhibited by scrotal cooling only. These dynamic responses were produced even by temperature changes as slow as 2 degrees C/min and only when the scrotum was warmed or cooled in the Tscr range above 35 degrees C. These dynamic responses are suggested to be a result of signal processing in supraspinal structures including POAH itself.