Ingram C D, Snowball R K, Mihai R
Department of Anatomy, University of Bristol, U.K.
Neuroscience. 1996 Nov;75(2):635-41. doi: 10.1016/0306-4522(96)00274-6.
In vitro extracellular recordings were made from tissue slices of suprachiasmatic nucleus from homozygous Brattleboro rats which are deficient in vasopressin. A high proportion (56%) of neurons were excited by application of exogenous vasopressin, indicating that the V1 receptors expressed by these neurons were functional. Basal activity of these vasopressin-sensitive neurons showed a marked circadian variation (higher during the subjective light phase) while vasopressin-insensitive neurons showed no significant variation, suggesting the presence of the V1 receptor identifies a population of highly circadian neurons. Suprachiasmatic neurons from both homozygous rats and their heterozygous (vasopressin-containing) litter mates displayed a circadian rhythm of spontaneous (basal) activity, with firing rates declining during the subjective dark phase, indicating that the endogenous pacemaker driving the circadian rhythm was not dependent upon the presence of vasopressin. However, the peak of spontaneous activity displayed during the subjective light phase was significantly lower in the vasopressin-deficient animals. These data show that the presence of endogenous vasopressin within the suprachiasmatic nucleus is not necessary for the generation of the circadian pattern of activity. However, vasopressin does function to amplify the rhythm by its excitatory effect during the light phase.
对纯合子布拉德福德大鼠视交叉上核的组织切片进行了体外细胞外记录，这些大鼠缺乏抗利尿激素。高比例（56%）的神经元在施加外源性抗利尿激素后被激活，表明这些神经元表达的V1受体具有功能。这些对抗利尿激素敏感的神经元的基础活动表现出明显的昼夜节律变化（在主观光照期较高），而对抗利尿激素不敏感的神经元则没有显著变化，这表明V1受体的存在确定了一群高度昼夜节律的神经元。纯合子大鼠及其杂合子（含抗利尿激素）同窝仔鼠的视交叉上神经元均表现出自发（基础）活动的昼夜节律，在主观暗期放电率下降，这表明驱动昼夜节律的内源性起搏器并不依赖于抗利尿激素的存在。然而，在主观光照期显示的自发活动峰值在抗利尿激素缺乏的动物中明显较低。这些数据表明，视交叉上核内源性抗利尿激素的存在对于昼夜活动模式的产生不是必需的。然而，抗利尿激素确实通过其在光照期的兴奋作用来放大节律。
