A STUDY ON THE MECHANISM UNDERLYING MILK EJECTION BURSTS OF OXYTOCIN CELLS.

为了研究哺乳大鼠哺乳过程中催产素神经元爆发活动的神经机制，我们进行了以下三个方面的研究：(1)中脑半横切对哺乳期大鼠催产素神经元射乳爆发幅度和时间过程的影响。利用哺乳期大鼠视上核对催产素神经元的电活动进行了细胞外记录，并对中脑半切除大鼠的泌乳爆发进行了研究。损伤侧催产素神经元记录的爆发比非损伤侧记录的爆发幅度小，发作时间晚，爆发持续时间短。这些结果表明，催产素神经元爆发的幅度和时间过程主要取决于来自对侧乳头的哺乳信息。(2)单侧哺乳对正常大鼠催产素神经元泌乳爆发的影响。当幼崽仅在记录的催产素神经元的同侧或对侧乳头时，爆发幅度明显低于双侧哺乳时。此外，同侧哺乳时的爆发幅度明显低于对侧哺乳时。研究结果表明，爆发幅度主要取决于从记录侧对面的奶嘴传入的哺乳信号的数量。(3)下丘脑半球间切片对视上催产素神经元泌乳爆发的影响。广泛的半球间切断术并没有消除双侧和对侧哺乳期间催产素神经元的爆发，但减少了同侧哺乳期间显示爆发的催产素神经元的数量。结果表明，在下丘脑的每一侧都有两个独立的门和求和机制。

In order to study the neural mechanisms to generate burst activities of oxytocin neurones during suckling in lactating rats, the following three studies were made :(1) the effect of midbrain-hemitransection on amplitudes and time courses of milk ejection bursts of oxytocin neurones in lactating rats.Extracellular recordings of the electrical activity of oxytocin neurones were made from the supraoptic nuclei of lactating rats, and the milk-ejection bursts were investigated in the midbrain-hemitransected rats. Of the burst recorded from oxytocin neurones on the lesioned side, the amplitude was smaller, the onset time was later and the burst span was shorter than those recorded on the non-lesion-ed side. These results indicated that the amplitude and time course of the burst of oxytocin neurones mainly depend on suckling information from the nipples on their opposite side.(2) the effects of unilateral suckling on milk ejection bursts of oxytocin neurones in intact rats.When application of pups was limited to the nipples on either the same side or the side opposite to the oxytocine neurone recorded, the burst amplitude was significantly lower than during bilateral suckling. Furthermore, the burst amplitude was significantly lower during ipsilateral suckling than during contralateral suckling. The finding indicates that the burst amplitude mainly depends on the amount of afferent suckling signals arising from the nipplies on the side opposite to the reocording side.(3) the effect of interhemispheric sections of the hypothalamus on milk-ejection bursts of supraoptic oxytocin neurones.Extensive interhemispheric sectioning did not abolish the burst of oxytocin neurones during bilateral and contralateral suckling but reduced the number of oxytocine neurones that showed the burst during ipsilateral suckling. The result suggest that there are two separate gate and summation mechanisms on each side of the hypothalamus.