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）对体温调节中枢作用的神经回路，本实验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）的神经回路进行了详细研究。1.刺激和错位实验：电刺激或化学刺激CG引起皮肤血管舒张。另一方面，电刺激或化学刺激腹侧被盖区引起皮肤血管收缩。当用Haras刀切断CG时，POA局部热刺激引起的血管舒张作用消失。由于VTA尾部的脱位，周围皮肤血管自发扩张。2.电生理实验：记录腹侧被盖区对电刺激的逆行反应。POA内的温敏神经元对局部升温有反应，其传导速度趋于缓慢。对电刺激作出顺行反应的温敏神经元表现为4种类型的反应：电刺激后44%的神经元表现为易化，13%表现为抑制，18%表现为易化后抑制，25%表现为易化后抑制。这些结果表明，POA与温度调节皮肤血管运动有关的传出神经回路有两条：一条是VTA的抑制回路，另一条是CG的易化回路。大部分的POA神经元的温度调节血管运动也被证明是易化反应的电刺激在SA。进一步研究POA-SA区可能有助于了解GnRH在体温调节中的中枢作用。

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.