Study for the afferent hypothalamic pathway for the milk-ejection reflex in the rat

我们以前曾报道，下丘脑背内侧核(DMH)是大鼠排乳反射传入通路的最终中继点(1992年，Takano等人)。本实验观察DMH是否投射到双侧下丘脑视上核(SON)，并参与催产素(OT)细胞在排乳反射时的同步激活。在乌拉坦麻醉的哺乳期大鼠，记录SON内单个OT细胞的胞外记录。在52个OT细胞中，有26个表现为顺行兴奋(OD+)或先抑制后兴奋(OD-+)，反应是对记录侧双侧DMH的电刺激。仅同侧DMH刺激记录侧有11个细胞呈OD+或OD-+反应。以10~50赫兹持续电刺激同侧和对侧DMH 30~60次，S可增加12 O…中7次的放电频率检测了更多的T细胞。40个DMH细胞投射到同侧SON，其中4个投射到对侧SON，4个细胞投射到对侧SON，其中25个细胞在乳汁喷射反射时被检测到放电模式。其中一个细胞向对侧SON投射，在排出乳汁之前，放电率(类似于催产素细胞的爆发活动)突然增加。该细胞对哺乳刺激的反应也表现出基础放电频率的增加。两个有双侧投射蛋白的细胞和一个有同侧投射蛋白的细胞在排乳前表现出放电率降低。其中一个投射对侧SON的细胞显示，对哺乳刺激的反应导致放电频率降低。结果提示，DMH能神经元投射到下丘脑两侧的OT细胞，这些投射可能参与了OT细胞在排乳反射过程中的同步激活。较少

We have previously reported that the dorsomedial hypothalamic nucleus (DMH) is the final relay site for the afferent pathway of the milk-ejection reflex in the rat (1992, Takano et al). The present experiments were undertaken to examine whether the DMH projects to supraoptic nuclei (SON) in both sides of the hypothalamus and contributes to the synchronized activation of oxytocin (OT) cells at milk-ejection reflex. In urethane anesthetized lactating rats, extracellular recordings of single OT cells in the SON were made. Twenty-six of 52 OT cells showed orthodromic excitation (OD+) or inhibition followed by the excitation (OD-+) in response to electrical stimulation of both ipsi-and contralateral DMH to the recording side. Eleven cells showed OD+ or OD-+ in responses to electrical stimulation of only ipsi-lateral DMH to the recording side. Continuous electrical stimulation of both ipsi- and contralateral DMH to the recording side at 10-50 Hz for 30-60 s increased firing rate in 7 of 12 O … More T cells tested. Fourty DMH cells were identified as projecting to the ipsilateral SON and 4 of them were also identified as projecting to the contralateral SON.Four cell were identified as projecting only to the contralateral SON.Of these, 25 were tested for theri firing pattern during milk ejection reflex. One cell, which had a projection to the contralateral SON, showed abrupt increase in firing rate (bursting activity similar to oxytocin cells) preceding milk ejection. This cell also showed an increase of basal firing rate in response to suckling stimulus. Two cells which had bilateral projectin and one cell which had a ipsilateral projectin showed reduction in firing rate preceding milk ejection. One cell which projected contralateral SON showed a reduction of firing rate in response to suckling stimulus. The results suggest that some of DMH neurones project to OT cells in both sides of hypothalamus and that these projections may contribute to the synchronized activation of OT cells during milk-ejection reflex. Less