Oldfield B J, Hards D K, McKinley M J
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Vic., Australia.
Brain Res. 1991 Aug 30;558(1):13-9. doi: 10.1016/0006-8993(91)90708-4.
The subfornical organ, along with other regions of the lamina terminalis, may contain osmoreceptors and is likely to be a site of action of blood-borne angiotensin II. The neural pathways by which these stimuli lead to vasopressin secretion, have been suggested to extend from the subfornical organ to hypothalamic sites of vasopressin production either directly or via synapses in an intervening nucleus such as the median preoptic nucleus. In the present study, cholera toxin conjugated to horseradish peroxidase (CT/HRP) or colloidal gold (CT/Au) has been injected, respectively, into the subfornical organ and supraoptic nucleus of the same animal. The anterograde and retrograde transport of the toxin from these two sites has made possible the identification, at the ultrastructural level, of a synapse in the median preoptic nucleus interposed in the pathway between the subfornical organ and the supraoptic nucleus. Moreover, the presence of retrogradely transported CT/HRP and CT/Au in the same neurone in the median preoptic nucleus indicates that some neurones in this nucleus have axons with collateral branches to both the subfornical organ and supraoptic nucleus. Either or both of these pathways may transmit information related to the tonicity of the blood or circulating levels of angiotensin II to sites in the hypothalamus.
穹窿下器与终板的其他区域一样，可能含有渗透压感受器，很可能是血源性血管紧张素II的作用部位。这些刺激导致抗利尿激素分泌的神经通路，有人认为是从穹窿下器直接或通过中间核（如视前正中核）中的突触延伸至下丘脑抗利尿激素产生部位。在本研究中，分别将与辣根过氧化物酶结合的霍乱毒素（CT/HRP）或胶体金（CT/Au）注入同一只动物的穹窿下器和视上核。毒素从这两个部位的顺行和逆行运输使得在超微结构水平上识别出视前正中核中位于穹窿下器和视上核之间通路中的一个突触成为可能。此外，视前正中核中同一神经元内存在逆行运输的CT/HRP和CT/Au，表明该核中的一些神经元具有向穹窿下器和视上核发出侧支的轴突。这些通路中的一条或两条都可能将与血液渗透压或循环中血管紧张素II水平相关的信息传递到下丘脑的部位。
