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

在大多数脊椎动物中已经报道了含有促性腺激素释放激素（GnRH）的神经元。虽然这些细胞含有GnRH，但它们似乎并不直接控制垂体释放促性腺激素，但可能参与对行为（如性行为）的神经调节作用。这个肽能系统的功能仍然相当模糊，部分原因是由于对该系统的输入和输出途径的配对知识。1)研究了medaka和金鱼的gnrh免疫反应末梢神经细胞（TN细胞）的传入来源。研究发现，与medaka有密切关系的硬骨鱼（percomorphs）中，medaka接受来自中脑被盖终核的输入，中脑输入可能将视觉和体感输入传递给medaka的TN细胞（percomorphs）。然而，研究发现金鱼缺乏被终核，相反，TN大鼠可以接受间脑、肾小球前核复合体的纤维，肾小球前核可以接受多种方式的输入，包括视觉、体感和侧线输入。虽然神经回路可能不同，但对TN细胞的多模态输入可能是硬骨鱼共有的特征。2)利用免疫组织化学方法研究了GnRH受体亚型（gnrrh）在过共形态硬骨鱼中的分布，发现侏儒gourami gnrbrimmunomunoreactive神经元分布于多种脑结构中，主要分布在视前区和内脏次级总核。视前区是生殖行为的中枢。这些发现表明，多模态感觉输入可能影响TN细胞的活动，导致行为（如性动机）和内脏感觉处理的调节。

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.