title: Activation of central warm-sensitive neurons and the tail vasomotor response in rats during brain and scrotal thermal stimulation.
abstract: The effects of preoptic and hypothalamic thermal stimulation on tail skin temperature were observed at different scrotal temperatures. The threshold hypothalamic temperature for tail vasodilation at a scrotal temperature of 40 degrees C was significantly lower than that at a scrotal temperature of either 25 degrees C or 33 degrees C. The effects of scrotal thermal stimulation on tail skin vasodilated by higher hypothalamic temperatures were observed. Cooling the scrotum from 42 to 30 degrees C invariably caused a rapid fall in tail temperature, whereas scrotal cooling from 30 to 25 degrees C did not cause any significant change. Cooling of either the left or right half of the scrotum caused a similar fall in tail temperature. The temperature characteristics of the preoptic hypothalamic thermo-sensitive neurons were determined at scrotal temperatures of 32, 36 and 26 degrees C. The firing rate of warm-sensitive neurons at a given hypothalamic temperature was highest at a scrotal temperature of 36 degrees C, while that of cold-sensitive neurons was lowest at that temperature. The scrotal temperature range over which the number of neurons activated by scrotal warming increased rapidly was between 36 and 39 degrees C when hypothalamic temperature was held at 36-37 degrees C.
mesh_terms: D000818:Animals; D001831:Body Temperature; D001921:Brain / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology; D008297:Male; D009474:Neurons / Q000502:physiology; D010812:Physical Stimulation; D011301:Preoptic Area / Q000502:physiology; D051381:Rats / Q000502:physiology*; D012611:Scrotum / Q000502:physiology*; D012881:Skin Temperature; D013623:Tail / Q000502:physiology*; D013696:Temperature; D014666:Vasomotor System / Q000502:physiology*