Mihai R, Coculescu M, Wakerley J B, Ingram C D
Department of Anatomy, School of Medical Sciences, University of Bristol, U.K.
Neuroscience. 1994 Oct;62(3):783-92. doi: 10.1016/0306-4522(94)90476-6.
The excitatory effect of [Arg8]-vasopressin and its potential contribution to the circadian cycle of electrical activity in the suprachiasmatic nucleus of the rat was investigated using extracellular recordings from hypothalamic slices from virgin female rats. The majority of neurons tested for their responses to vasopressin and [Arg8]-vasotocin displayed coincident, dose-dependent excitation by both peptides, although the relative efficacy varied between neurons, with some showing a highly preferential excitation by vasotocin. Perifusion with the vasopressin receptor antagonist d(CH2)5[Tyr(OEt)2,Val4,Cit8]-vasopressin was able to block the majority of responses to vasopressin or vasotocin (20/25), and similar excitation could be induced by the selective agonist [Phe2,Orn8]-vasotocin, indicating a mainly V1 receptor-mediated effect. Few neurons (3/27; 11%) responded to the oxytocin-specific agonist, [Thr4,Gly7]-oxytocin, suggesting a low occurrence of oxytocin receptors. In addition to blocking the action of exogenous vasopressin, the V1 antagonist caused a reversible suppression of spontaneous basal activity in 7/25 cases, consistent with the presence of an endogenous excitatory vasopressin tone. In agreement with previous reports, the activity of suprachiasmatic nucleus neurons showed a significant correlation between spontaneous activity and the light-dark cycle, with activity decreasing during the subjective dark phase. When neurons were divided on the basis of their response to vasopressin and/or vasotocin, the peptide-sensitive neurons continued to show a strong correlation (r = 0.513, P < 0.01) while the insensitive neurons showed no correlation (r = 0.136, P > 0.05). These data confirm the presence of V1 type receptors in the suprachiasmatic nucleus and also indicate a small number of neurons possessing additional classes of receptor selective for either oxytocin or vasotocin. Contrary to previous reports, they also demonstrate that endogenous vasopressin tonically excites suprachiasmatic nucleus neurons. The fact that vasopressin-sensitive (but not vasopressin-insensitive) neurons show a level of basal activity correlated with time, suggests that this tone may contribute to the circadian cycle of electrical activity in the suprachiasmatic nucleus.
利用来自未交配雌性大鼠下丘脑切片的细胞外记录，研究了[精氨酸8] - 加压素的兴奋作用及其对大鼠视交叉上核电活动昼夜节律周期的潜在贡献。在测试对加压素和[精氨酸8] - 催产素反应的大多数神经元中，两种肽均呈现出一致的、剂量依赖性兴奋，尽管不同神经元之间相对效力有所不同，有些神经元对催产素表现出高度优先的兴奋。用加压素受体拮抗剂d(CH2)5[酪氨酸(乙酯)2,缬氨酸4,瓜氨酸8] - 加压素进行灌流能够阻断对加压素或催产素的大多数反应(20/25)，并且选择性激动剂[苯丙氨酸2,鸟氨酸8] - 催产素可诱导类似的兴奋，表明主要是V1受体介导的效应。很少有神经元(3/27; 11%)对催产素特异性激动剂[苏氨酸4,甘氨酸7] - 催产素产生反应，提示催产素受体的发生率较低。除了阻断外源性加压素的作用外，V1拮抗剂在7/25的情况下导致自发基础活动的可逆性抑制，这与内源性兴奋性加压素张力的存在一致。与先前的报告一致，视交叉上核神经元的活动在自发活动与明暗周期之间显示出显著相关性，在主观暗期活动降低。当根据神经元对加压素和/或催产素的反应进行划分时，对肽敏感的神经元继续显示出强相关性(r = 0.513, P < 0.01)，而不敏感的神经元则无相关性(r = 0.136, P > 0.05)。这些数据证实了视交叉上核中存在V1型受体，并且还表明少数神经元拥有对催产素或催产素具有选择性的其他类型受体。与先前的报告相反，它们还证明内源性加压素持续兴奋视交叉上核神经元。加压素敏感(但不是加压素不敏感)神经元显示出与时间相关的基础活动水平，这一事实表明这种张力可能有助于视交叉上核电活动的昼夜节律周期。
