Input and output neuronal circuitries and its evolution of a neuromodulatory terminal nerve GnRH system

神经元含有促性腺激素释放激素（GnRH）已被报道在大多数脊椎动物。虽然这些细胞含有GnRH，但它们似乎直接控制垂体促性腺激素的释放，但可能参与对行为（如性行为）的神经调节作用。这一肽能系统的功能仍然相当模糊，这在一定程度上是由于对该系统的输入和输出途径的知识1）在青鳉和金鱼中研究了GnRH免疫反应终末神经细胞（TN细胞）的传入来源。青少年被发现接受输入从中脑的背盖-终末核的percomorph硬骨鱼是密切相关的青少年中脑输入大概传达视觉和体感输入TN细胞的青少年percomorph。然而，金鱼被发现缺乏被盖终核，相反，TN大鼠被建议接受来自间脑的纤维，肾小球前核复合体，肾小球前核后接受多种方式，包括视觉，体感和侧线输入。2）应用免疫组织化学方法研究了硬骨鱼类GnRH受体亚型（GnRHRs）的分布。结果表明，在硬骨鱼类中，GnRHRs主要分布于视前区和次级内脏总核。视前区是生殖行为的中枢，多通道感觉输入可能影响TN细胞的活动，从而调节行为（如性动机）和内脏感觉的加工。

Neurons that contain gonadotropin-releasing hormone (GnRH) have been reported in most vertebrates. Although these cells contain GnRH, they do rot appear to control directly the gonadotropin release from the pituitary but may be involved in neuromodulatory action on behavior, e.g. sexual behavior. The functions of this peptidergic system still remain rather obscure, and this is due, in part, to pair knowledge on the input and output pathways of this system1) Afferent sources to the GnRH-immunoreactive terminal nerve cells (TN cells) were studied in medaka and goldfish. The medaka was found to receive inputs from the nucleus tegmento-terminalis of the midbrain as in percomorph teleosts that am closely related to medaka Midbrain inputs presumably convey visual and somatosensory inputs to TN cells of medaka as in percomorphs. However, the goldfish was found to lack a nucleus tegmento-terminalis Instead, TN rats were suggested to receive fibers from the diencephalic, preglomerular nuclear complex, and preglomerular nuclei were hind to receive multiple modalities including visual, somatosensory, and lateral line inputs. Although neural circuitries may be different, multimodal inputs to the TN cells may be a character shared in teleosts.2) Distribution of GnRH receptor subtypes (GnRHRs) were studied by means of immunohistocehmistry in a percomorph teleost, the dwarf gourami GnRBRimmunoreactive neurons were detected in a number of brain structures and mainly in the preoptic area and the secondary general visceral nucleus. The preoptic area is known to central reproductive behavior.These findings suggest that multimodal sensory inputs presumably affect the activities TN cells, resulting in the modulation of behavior (e.g. sexual motivation) and processing of visceral senses.