White J, Meredith M
Department of Biological Science, Florida State University, Tallahassee 32306.
J Comp Neurol. 1995 Jan 16;351(3):385-403. doi: 10.1002/cne.903510306.
The nervus terminalis is a ganglionated vertebrate cranial nerve of unknown function that connects the brain and the peripheral nasal structures. To investigate its function, we have studied nervus terminalis ganglion morphology and physiology in the bonnethead shark (Sphyrna tiburo), where the nerve is particularly prominent. Immunocytochemistry for gonadotropin-releasing hormone (GnRH) and Leu-Pro-Leu-Arg-Phe-NH2 (LPLRFamide) revealed two distinct populations of cells. Both were acetylcholinesterase positive, but LPLR-Famide-immunoreactive cells consistently stained more darkly for acetylcholinesterase activity. Tyrosine hydroxylase immunocytochemistry revealed fibers and terminal-like puncta in the ganglion, primarily in areas containing GnRH-immunoreactive cells. Consistent with the anatomy, in vitro electrophysiological recordings provided evidence for cholinergic and catecholaminergic actions. In extracellular recordings, acetylcholine had a variable effect on baseline ganglion cell activity, whereas norepinephrine consistently reduced activity. Electrical stimulation of the nerve trunks suppressed ganglion activity, as did impulses from the brain in vivo. During electrical suppression, acetylcholine consistently increased activity, and norepinephrine decreased activity. Muscarinic and, to a lesser extent, alpha-adrenergic antagonists both increased activity during the electrical suppression, suggesting involvement of both systems. Intracellular recordings revealed two types of ganglion cells that were distinguishable pharmacologically and physiologically. Some cells were hyperpolarized by cholinergic agonists and unaffected by norepinephrine; these cells did not depolarize with peripheral nerve trunk stimulation. Another group of cells did depolarize with peripheral trunk stimulation; a representative of this group was depolarized by carbachol and hyperpolarized by norepinephrine. These and other data suggest that the bonnethead nervus terminalis ganglion contains at least two cell populations that respond differently to acetylcholine and norepinephrine. The bonnethead nervus terminalis ganglion appears to differ fundamentally from sensory and autonomic ganglia but does share some features with the neural circuits of forebrain GnRH systems.
终神经是一种具有神经节的脊椎动物脑神经，其功能未知，连接大脑和外周鼻结构。为了研究其功能，我们在窄头双髻鲨（Sphyrna tiburo）中研究了终神经节的形态和生理学，在这种鲨鱼中该神经尤为突出。促性腺激素释放激素（GnRH）和亮-脯-亮-精-苯丙氨酸-酰胺（LPLRFamide）的免疫细胞化学显示出两种不同的细胞群。两者均为乙酰胆碱酯酶阳性，但LPLR-Famide免疫反应性细胞的乙酰胆碱酯酶活性染色始终更深。酪氨酸羟化酶免疫细胞化学显示神经节中有纤维和终末样小点，主要位于含有GnRH免疫反应性细胞的区域。与解剖结构一致，体外电生理记录为胆碱能和儿茶酚胺能作用提供了证据。在细胞外记录中，乙酰胆碱对神经节细胞的基线活动有可变影响，而去甲肾上腺素始终降低活动。神经干的电刺激抑制神经节活动，体内来自大脑的冲动也有同样作用。在电抑制期间，乙酰胆碱始终增加活动，而去甲肾上腺素降低活动。毒蕈碱拮抗剂以及在较小程度上的α-肾上腺素能拮抗剂在电抑制期间均增加活动，表明这两个系统均参与其中。细胞内记录显示出两种在药理学和生理学上可区分的神经节细胞类型。一些细胞被胆碱能激动剂超极化且不受去甲肾上腺素影响；这些细胞在周围神经干刺激时不会去极化。另一组细胞在周围神经干刺激时会去极化；该组中的一个代表被卡巴胆碱去极化并被去甲肾上腺素超极化。这些以及其他数据表明，窄头双髻鲨终神经节至少包含两个对乙酰胆碱和去甲肾上腺素反应不同的细胞群。窄头双髻鲨终神经节似乎与感觉神经节和自主神经节有根本区别，但确实与前脑GnRH系统的神经回路有一些共同特征。
