Kawakami M, Sakuma Y, Akema T
Brain Res. 1978 Aug 11;151(3):533-44. doi: 10.1016/0006-8993(78)91085-5.
Antidromic responses were induced in the medial basal hypothalamus (MBH) of female rats by median eminence (ME) stimulation, and thresholds were measured under various endocrine conditions. Two different types of antidromic response were recognized. In 83 out of 97 responses, repetitive shocks to the ME at 20--40 Hz induced a fractionation of antidromically-driven spikes into A- and B-components. In the remainder, the antidromically activated spikes were stable to stimulation at high frequency. The threshold tended to show higher values in proestrus than in diestrus-I in both types of response. However, only in the former type of response, application of conditioning electrical shocks to the ME was effective in decreasing the threshold for successive test pulses. A decrease in the threshold lasted for 150--200 msec following the conditioning, with the lowest threshold at about 60 msec after the shock. Effects of the conditioning persisted in animals with chronic complete deafferentation of the MBH but were abolished in intact rats by reserpine treatment. Dopamine, but not norepinephrine or serotonin, mimicked the threshold-decreasing effect of the conditioning when applied to the ME. The results suggest the possibility of a depolarizing effect of some dopaminergic neural mechanism projecting from the MBH to the ME and acting on the axons of a particular type of MBH neuron characterized by fractionating spikes.
通过刺激正中隆起（ME）在雌性大鼠的内侧基底下丘脑（MBH）中诱导逆向反应，并在各种内分泌条件下测量阈值。识别出两种不同类型的逆向反应。在97次反应中的83次中，以20 - 40 Hz的频率对ME进行重复刺激会使逆向驱动的尖峰分裂为A成分和B成分。在其余反应中，逆向激活的尖峰对高频刺激稳定。在两种反应类型中，发情前期的阈值往往比动情间期I更高。然而，仅在前者类型的反应中，对ME施加条件性电刺激可有效降低连续测试脉冲的阈值。条件刺激后阈值降低持续150 - 200毫秒，休克后约60毫秒时阈值最低。条件刺激的效果在MBH慢性完全去传入的动物中持续存在，但在完整大鼠中通过利血平处理被消除。当应用于ME时，多巴胺而非去甲肾上腺素或5-羟色胺模拟了条件刺激的阈值降低效应。结果表明，从MBH投射到ME并作用于以尖峰分裂为特征的特定类型MBH神经元轴突的某些多巴胺能神经机制可能具有去极化作用。
