Laboratory of Information Biology, Graduate School of Information Sciences, Tohoku University, Sendai, Japan.
Super-Network Brain Physiology, Graduate School of Life Sciences, Tohoku University, Sendai, Japan.
J Neuroendocrinol. 2023 Dec;35(12):e13351. doi: 10.1111/jne.13351. Epub 2023 Oct 30.
Serotonergic neurons originating from the raphe nuclei have been proposed to regulate corticotropin-releasing factor (CRF) neurons in the paraventricular nucleus of the hypothalamus (PVH). Since glutamate- and γ-aminobutyric acid (GABA)-containing neurons, constituting the hypothalamic local circuits, innervate PVH CRF neurons, we examined whether they mediate the actions of serotonin (5-hydroxytryptamine [5-HT]) on CRF neurons. Spontaneous excitatory postsynaptic currents (sEPSCs) or spontaneous inhibitory postsynaptic currents (sIPSCs) were recorded in PVH CRF neurons, under whole cell patch-clamp, using the CRF-modified yellow fluorescent protein (Venus) ΔNeo mouse. Serotonin elicited an increase in the frequency of sEPSCs in 77% of the cells and a decrease in the frequency of sIPSCs in 71% of the cells, tested in normal medium. Neither the amplitude nor decay time of sEPSC and sIPSC was affected, thus the site(s) of action of serotonin may be presynaptic. In the presence of tetrodotoxin (TTX), serotonin had no significant effects on either parameter of sEPSC or sIPSC, indicating that the effects of serotonin are action potential-dependent, and that the presynaptic interneurons are largely intact within the slice; distant neurons may exist, though, since some 20%-30% of neurons did not respond to serotonin without TTX. We next examined through what receptor subtype(s) serotonin exerts its effects on presynaptic interneurons. DOI (5-HT agonist) mimicked the action of serotonin on the sIPSCs, and the serotonin-induced decrease in sIPSC frequency was inhibited by a selective 5-HT antagonist RS102221. 8-OH-DPAT (5-HT agonist) mimicked the action of serotonin on the sEPSCs, and the serotonin-induced increase in sEPSC frequency was inhibited by a selective 5-HT antagonist SB269970. Thus, serotonin showed a dual action on PVH CRF neurons, by upregulating glutamatergic- and downregulating GABAergic interneurons; the former may partly be mediated by 5-HT receptors, whereas the latter by 5-HT receptors. The CRF-Venus ΔNeo mouse was useful for the electrophysiological examination.
来自中缝核的血清素能神经元被认为可以调节下丘脑室旁核（PVH）中的促肾上腺皮质释放因子（CRF）神经元。由于谷氨酸和γ-氨基丁酸（GABA）能神经元构成了下丘脑局部回路，它们投射到 PVH CRF 神经元，因此我们研究了它们是否介导了血清素（5-羟色胺[5-HT]）对 CRF 神经元的作用。在使用 CRF 修饰的黄色荧光蛋白（Venus）ΔNeo 小鼠的全细胞膜片钳记录中，我们在 PVH CRF 神经元中记录自发兴奋性突触后电流（sEPSC）或自发抑制性突触后电流（sIPSC）。在正常培养基中，血清素可使 77%的细胞的 sEPSC 频率增加，使 71%的细胞的 sIPSC 频率降低。sEPSC 和 sIPSC 的幅度和衰减时间均不受影响，因此血清素的作用部位可能是突触前。在加入河豚毒素（TTX）后，血清素对 sEPSC 或 sIPSC 的任何参数均无明显影响，表明血清素的作用依赖于动作电位，并且切片中大部分突触前中间神经元仍然完整；尽管存在一些 20%-30%的神经元在没有 TTX 的情况下对血清素没有反应，但是可能存在远距离神经元。接下来，我们通过什么受体亚型（s）研究了血清素对突触前中间神经元的作用。DOI（5-HT 激动剂）模拟了血清素对 sIPSC 的作用，而选择性 5-HT 拮抗剂 RS102221 抑制了血清素引起的 sIPSC 频率降低。8-OH-DPAT（5-HT 激动剂）模拟了血清素对 sEPSC 的作用，而选择性 5-HT 拮抗剂 SB269970 抑制了血清素引起的 sEPSC 频率增加。因此，血清素对 PVH CRF 神经元具有双重作用，上调谷氨酸能神经元并下调 GABA 能神经元；前者可能部分由 5-HT 受体介导，而后者由 5-HT 受体介导。CRF-VenusΔNeo 小鼠对电生理检查很有用。
