Neurophysiological analysis on neuronal circuits related to thermoregulatory actions of central gonadotropin releasing hormone.

为阐明促性腺激素释放激素(GnRH)对体温调节的中枢作用，对大鼠下丘脑视前区(POA)、中脑中央灰质(CG)、腹侧被盖区(VTA)和隔区(SA)的神经元回路进行了详细研究。1.刺激脱位实验：电刺激或化学刺激CG引起皮肤血管扩张。另一方面，VTA中的电或化学刺激引起皮肤血管收缩。当用Haras型刀切断CG时，局部热刺激引起的POA血管扩张作用消失。由于尾侧VTA脱位，周围皮肤血管自发扩张。2.电生理实验：记录视网膜区POA对电刺激的逆行反应的细胞外神经元活动。POA内对局部变暖有反应的温敏神经元往往表现为传导速度较慢的反应。对SA内电刺激顺行反应的温敏神经元有4种反应类型：易化后44%，抑制后13%，易化后抑制18%，抑制后易化25%。这些结果表明，POA有两个与温度调节皮肤血管运动有关的传出回路，一个是对VTA的抑制回路，另一个是对CG的易化回路。与温度调节血管运动有关的大多数POA神经元也对SA内的电刺激有易化反应。利用切片标本对POA-SA区的进一步研究可能会为GnRH在体温调节中的中枢作用提供更多的信息。

To clarify the neuronal circuits related central actions of gonadotropin releasing hormone (GnRH) on thermoregulation, neuronal circuits in the preoptic area (POA) in the hypothalamus, central grey (CG) and ventral tegmental area (VTA) in the midbrain, and septal area (SA) were investigated in detail using rats. 1.Stimulation and dislocation experiment : Electrical or chemical stimulations in the CG elicited skin vasodilations. On the other hand electrical or chemical stimulations in the VTA elicited skin vasoconstrictions. When the CG was cut by Haras-type knife, vasodilations which had been induced by the local thermal stimulation in the POA were disappeared. By the dislocation in the caudal VTA, peripheral skin vessels dilated spontaneously. 2.Electrophysiological experiment : The extracellular neuronal actions in the POA which retrogradely responded to electrical stimulations in the VTA were recorded. The warm-sensitive neurons in the POA, which responded to the local warming, tended to show responses with a slow conduction velocity. The warm-sensitive neurons which responded antegradely to the electrical stimulations in the SA showed four types of responses; 44% were facilitated, 13% inhibited, 18% inhibited after facilitation and 25% facilitated after inhibition by the electrical stimulation in the SA. These results indicated that there were two efferent neuronal circuits from POA related to thermoregulatory skin vasomotions; one is the inhibitory circuit to the VTA and the other is the facilitatory circuit to the CG. Majority of the POA neurons concerning thermoregulatory vasomotions were also shown to respond facilitatorily to the electrical stimulations in SA. The further investigations focused on POA-SA area using slice specimen may give more information to the central effects of GnRH on thermoregulation.