Smith B N, Armstrong W E
Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38163.
Neuroscience. 1990;38(2):469-83. doi: 10.1016/0306-4522(90)90043-4.
Previous studies of the tuberal, or retrochiasmatic, portion of the supraoptic nucleus suggest its functional similarity to the more densely populated anterior supraoptic nucleus, but the basic electrophysiological and morphological features of tuberal supraoptic nucleus neurons have not been described. Using the hypothalamo-neurohypophysial explant preparation in the rat, intracellular recordings and biocytin injections were made in tuberal supraoptic nucleus neurons and the results indicate that the two parts of the nucleus are similar. The generally oval-shaped somata of tuberal supraoptic nucleus neurons exhibited short, irregularly shaped appendages, and possessed 2-5 varicose, sparsely branching dendrites oriented in the horizontal plane. Many tuberal supraoptic nucleus neurons could be antidromically stimulated (mean latency = 6.4 ms). Filled neurons had varicose axons which were traced to the median eminence and even as far as the neural stalk, but which did not bifurcate. Both axons and dendrites were sparsely invested with short, hair-like appendages. The input resistance of the recorded neurons (mean = 177.7 M omega) was positively correlated with the membrane time constant (mean = 13.1 ms; r = 0.83). Tuberal supraoptic nucleus neurons displayed a prominent afterhyperpolarization following individual spikes or bursts of spikes, as well as firing frequency adaptation in response to positive current pulses. Although numbering far fewer than those of the anterior supraoptic nucleus, tuberal supraoptic nucleus neurons have axons which are more often intact in this preparation, and a dendritic tree which radiates within the plane of the explant. Thus these neurons should provide a useful model for further study of the electrophysiological and morphological characteristics of mammalian neurosecretory neurons.
以往对视上核结节部或视交叉后区的研究表明，它在功能上与细胞分布更密集的视上核前部相似，但结节部视上核神经元的基本电生理和形态学特征尚未见描述。利用大鼠下丘脑 - 神经垂体体外培养标本，对结节部视上核神经元进行了细胞内记录和生物胞素注射，结果表明该核的这两个部分相似。结节部视上核神经元的胞体通常呈椭圆形，有短的、形状不规则的附属物，并有2 - 5条曲张的、稀疏分支的树突，这些树突在水平面内排列。许多结节部视上核神经元可被逆向刺激（平均潜伏期 = 6.4毫秒）。被标记的神经元有曲张的轴突，追踪发现其延伸至正中隆起，甚至可达神经柄，但并不分支。轴突和树突上都稀疏地分布着短的、毛发状的附属物。所记录神经元的输入电阻（平均 = 177.7兆欧）与膜时间常数（平均 = 13.1毫秒；r = 0.83）呈正相关。结节部视上核神经元在单个动作电位或动作电位爆发后表现出明显的超极化后电位，并且对正向电流脉冲有放电频率适应性。尽管结节部视上核神经元的数量远少于视上核前部的神经元，但在这个标本中，结节部视上核神经元的轴突更常保持完整，其树突在培养标本平面内呈放射状分布。因此，这些神经元应为进一步研究哺乳动物神经分泌神经元的电生理和形态学特征提供一个有用的模型。
