In the supraoptic nucleus (SON), the incidence of dye coupling among oxytocin (OT) neurons increases significantly in nursing mothers. However, the type(s) of connexin (Cx) involved is(are) unknown. In this study, we specifically investigated whether Cx36 plays a functional role in the coupling between OT neurons in the SON of lactating rats. In this brain region, Cx36 was mainly coimmunostained with vasopressin neurons in virgin female rats, whereas in lactating rats, Cx36 was primarily colocalized with OT neurons. In brain slices from lactating rats, application of quinine (0.1 mM), a selective blocker of Cx36, significantly reduced dye coupling among OT neurons as well as the discharge/firing frequency of spikes/action potentials and their amplitude, and transiently depolarized the membrane potential of OT neurons in whole-cell patch-clamp recordings. However, quinine significantly reduced the amplitude, but not frequency, of inhibitory postsynaptic currents in OT neurons; the duration of excitatory postsynaptic currents was reduced but not their frequency and amplitude. Furthermore, the excitatory effect of OT (1 pM) on OT neurons was significantly weakened and delayed by quinine, and burst firing was absent in the presence of this inhibitor. Lastly, Western blotting analysis revealed that the presence of combined, but not alone, quinine and OT significantly reduced the amount of Cx36 in the SON. Thus, Cx36-mediated junctional communication plays a crucial role in autoregulatory control of OT neuronal activity, likely by acting at the postsynaptic sites. The level of Cx36 is modulated by its own activity and the presence of OT.

中文翻译：

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连接蛋白36在大鼠视上核中催产素神经元活性的自动调节中的作用。

在视上核（SON）中，催产素（OT）神经元之间染料偶联的发生率在哺乳母亲中显着增加。然而，所涉及的连接蛋白（Cx）的类型是未知的。在这项研究中，我们专门研究了Cx36是否在泌乳大鼠SON的OT神经元之间的偶联中发挥功能性作用。在这个大脑区域中，Cx36主要在未成年雌性大鼠中与血管加压素神经元共免疫，而在哺乳期大鼠中，Cx36主要与OT神经元共定位。在哺乳期大鼠的脑片中，应用奎宁（0.1 mM）（一种选择性的Cx36阻断剂）可显着降低OT神经元之间的染料偶联，以及降低突波/动作电位的放电/发射频率及其幅度，并在全细胞膜片钳记录中使OT神经元的膜电位暂时去极化。但是，奎宁可显着降低OT神经元抑制性突触后电流的幅度，但不会降低频率。兴奋性突触后电流的持续时间减少了，但频率和幅度没有减少。此外，奎宁可显着减弱和延迟OT（1 pM）对OT神经元的兴奋作用，并且在该抑制剂存在下不存在爆发放电。最后，Western印迹分析显示，奎宁和OT联合但不是单独存在，大大降低了SON中Cx36的含量。因此，Cx36介导的交界通讯在OT神经元活性的自动调节控制中起着至关重要的作用，可能是通过作用于突触后部位。