Armstrong W E, Stern J E
Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis, Tennessee 38163, USA.
J Neurophysiol. 1997 Nov;78(5):2427-37. doi: 10.1152/jn.1997.78.5.2427.
Electrophysiological and morphological characteristics of neurons in perinuclear zone of supraoptic nucleus. J. Neurophysiol. 78: 2427-2437, 1997. Neurons in the perinuclear zone (PZ) of the supraoptic nucleus (SON) are thought to serve as interneurons and may mediate changes in neurohypophysial hormone release in response to physiological changes in blood pressure. However, the morphology and electrophysiological characteristics of PZ neurons are unknown. In the present study, PZ neurons from male and female rats were recorded intracellularly to determine some membrane properties, then filled with biocytin or biotinamide for morphological analysis. In general, PZ neurons had faster spikes than magnocellular SON neurons, and the great majority were characterized by a subthreshold depolarizing hump when depolarized from a hyperpolarized (less than -80 mV) membrane potential. In most neurons, this hump was similar to low-threshold spikes described in other CNS regions. Near-threshold, fast action potentials were clustered near the onset of these depolarizations. Conspicuously absent in all PZ neurons was the strong transient and subthreshold outward rectification characteristic of vasopressin and oxytocin neurons of the SON. These results suggest that PZ neurons are electrophysiologically distinct from neurosecretory neurons of the SON. No differences were found between male and female rats in any of the basic properties examined, including input resistance, membrane time constant, spike height, spike width, spike threshold, and the size of the spike afterhyperpolarization. Morphologically, PZ neurons were diverse but were divided into spiny and aspiny groups. Three spiny neurons and one aspiny neuron contributed an axonal projection to the SON characterized by varicosities suggestive of terminals. In the case of the three spiny neurons, the SON projection was clearly a minor collateral projection. The axon arborized in the PZ, but one or more branches were cut at the edge of the explant, indicating a longer projection. In the remaining neurons, no axonal projection to the SON was detected and several had axons leaving the explant. Some portion of the dendritic tree penetrated the SON in several neurons. The morphology of PZ neurons was thus heterogeneous and suggests that, for some cells at least, the projection to the SON may be a minor collateral component of a much wider axonal projection.
视上核核周区神经元的电生理和形态学特征。《神经生理学杂志》78: 2427 - 2437, 1997年。视上核（SON）核周区（PZ）的神经元被认为起着中间神经元的作用，并且可能在血压发生生理变化时介导神经垂体激素释放的改变。然而，PZ神经元的形态和电生理特征尚不清楚。在本研究中，对雄性和雌性大鼠的PZ神经元进行细胞内记录以确定一些膜特性，然后用生物胞素或生物素酰胺填充以进行形态学分析。一般来说，PZ神经元的动作电位比大细胞性SON神经元更快，并且绝大多数在从超极化（小于 -80 mV）膜电位去极化时具有阈下去极化波峰的特征。在大多数神经元中，这种波峰类似于在其他中枢神经系统区域所描述的低阈值动作电位。接近阈值时，快速动作电位聚集在这些去极化开始附近。所有PZ神经元中明显缺乏SON中血管加压素和催产素神经元所特有的强瞬时性和阈下去极化外向整流特性。这些结果表明PZ神经元在电生理上与SON的神经分泌神经元不同。在包括输入电阻、膜时间常数、动作电位高度、动作电位宽度、动作电位阈值以及动作电位后超极化大小等所检测的任何基本特性方面，未发现雄性和雌性大鼠之间存在差异。在形态学上，PZ神经元多种多样，但可分为有棘和无棘两类。三个有棘神经元和一个无棘神经元向SON发出轴突投射，其特征为有提示终末的膨体。就这三个有棘神经元而言，向SON的投射显然是一个较小的侧支投射。轴突在PZ内分支，但有一个或多个分支在脑片边缘被切断，这表明投射更长。在其余神经元中，未检测到向SON的轴突投射，并且有几个神经元的轴突离开了脑片。在几个神经元中，树突树的一部分穿透了SON。因此，PZ神经元的形态是异质性的，这表明至少对于一些细胞来说，向SON的投射可能是更广泛轴突投射的一个较小的侧支成分。
