Imagawa T, Kitagawa H, Uehara M
Department of Veterinary Anatomy, Faculty of Agriculture, Tottori University, Japan.
J Anat. 1996 Feb;188 ( Pt 1)(Pt 1):149-56.
Nerve fibres and their connections with chromaffin cells in the carp head kidney were studied by light and electron microscopy. Some nerve bundles entered the head kidney from the dorsal aspect along veins. Many unmyelinated axons emerged from the nerve bundles to invade the clusters of chromaffin cells, the distribution of which was restricted to the neighbourhood of the venous trunks and their tributaries. Most of the nerve endings were attached to a chromaffin cell by synaptic junctions and were generally invaginated into the cell. Some nerve endings were flattened in shape and connected with two chromaffin cells. Occasional exocytotic figures of synaptic vesicles opening into the intercellular space, or synaptic junctions along the course of the nerve fibre were observed. The percentage of the chromaffin cells supplied by nerve endings in the head kidney as a whole was similar to that in primitive amphibians. The distribution of the chromaffin cells and the frequency of their innervation suggest that carp chromaffin cells are phylogenetically similar to those of amphibians. The frequencies of synaptic connections in the carp head kidney showed regional differences. The number in dorsal portion was significantly higher than that in two ventral portions. It is suggested that chromaffin cells in the head kidney are separable into two populations: one (in the dorsal portion) shows closer and the other (in the ventral portions) less contact with nerve fibres. The fine structure of the nerve endings indicates that catecholamine secretion of carp chromaffin cells is partially modulated by nerve fibres (probably preganglionic cholinergic fibres). However, the low frequency of synaptic connections on the chromaffin cells and their distribution suggest that carp chromaffin cells are mainly modulated by the endocrine system via the bloodstream.
利用光学显微镜和电子显微镜对鲤鱼头肾中的神经纤维及其与嗜铬细胞的连接进行了研究。一些神经束沿着静脉从背侧进入头肾。许多无髓轴突从神经束发出，侵入嗜铬细胞簇，嗜铬细胞的分布仅限于静脉干及其分支附近。大多数神经末梢通过突触连接附着在一个嗜铬细胞上，并且通常内陷到细胞中。一些神经末梢呈扁平状，与两个嗜铬细胞相连。偶尔观察到突触小泡向细胞间隙开放的胞吐图像，或沿神经纤维行程的突触连接。头肾中由神经末梢供应的嗜铬细胞百分比与原始两栖动物中的相似。嗜铬细胞的分布及其神经支配频率表明，鲤鱼嗜铬细胞在系统发育上与两栖动物的相似。鲤鱼头肾中突触连接的频率存在区域差异。背侧部分的数量明显高于两个腹侧部分。提示头肾中的嗜铬细胞可分为两个群体：一个（在背侧部分）与神经纤维的接触较紧密，另一个（在腹侧部分）与神经纤维的接触较少。神经末梢的精细结构表明，鲤鱼嗜铬细胞的儿茶酚胺分泌部分受神经纤维（可能是节前胆碱能纤维）调节。然而，嗜铬细胞上突触连接的低频率及其分布表明，鲤鱼嗜铬细胞主要通过血液循环受内分泌系统调节。
