Physiological and Biochemical Studies on Neuromodulatory Action of Terminal Nerve GnRH System

促性腺激素释放激素（GnRH）最初被纯化并确定为一种促垂体十肽激素，促进垂体释放促性腺激素。我们已经证明存在三解剖以及功能上不同的GnRH神经元系统在几种硬骨鱼物种。然后，我们使用了热带鱼（Colisa lalia）的大脑，因为这种鱼的末梢神经（TN） GnRH神经元很大，形成一个紧密的细胞簇，因此人们可以很容易地记录整个大脑中单个GnRH神经元的活动，在体外制备中使用锋利的微电极或贴片移液器。由于大多数脊椎动物的GnRH神经元细胞体较小且分布分散，因此从单个GnRH神经元进行记录是非常困难的。根据迄今为止获得的结果，我们提出了一个实验性的调节神经元模型，n - gnrh细胞，包括一些假设。n - gnrh细胞具有自发的振荡活性，这些活性或更多地源于其自身膜的固有离子通道特性。抗ttx的持久Na^+通道、I_<Na（慢）>和某种未知的K^+通道在起搏器活动的产生中起重要作用。由环境、信息素、激素等因素引发的鱼类生理状况的变化，可能通过激素和/或神经递质作用于调节神经元。作为调节神经元起搏器活动基础的离子通道的性质可能受到某种信号转导机制的改变。这将导致调节神经元能够改变自己的起搏器频率或在不同的放电模式之间切换。换句话说，动物的生理状况可能被编码在调节神经元放电的频率和/或模式中。反过来，这些调节神经元可以通过广泛的、多轴突分支同时调节多种脑区目标神经元的兴奋性。少

The gonadotropin-releasing hormone (GnRH) was originally purified and identified as a hypophysiotrophic decapeptide hormone that facilitates gonadotropin release from the pituitary. We have demonstrated the existence of three anatomically as well as functionally different GnRH neuronal systems in several teleost species. We then used the brain of a tropical fish (Colisa lalia) because the terminal nerve (TN) GnRH neurons of this fish are large and make a tight cell cluster so that one can readily record the activities of a single GnRH neuron in a whole brain in vitro preparation using sharp microelectrodes or patch pipettes. Because the GnRH neuronal cell bodies in most vertebrate species are small and diffusely distributed, it has been extremely difficult to record from a single GnRH neurons. From the results obtained thus far, we propose a tentative model of modulator neurons, TN-GnRH cells, including some hypotheses. The TN-GnRH cells have spontaneous oscillatory activities which or … More iginate from the intrinsic ionic channel properties of their own membranes. A TTX-resistant persistent Na^+ channel, I_<Na(slow)>, and some kind of unidentified K^+ channel play important roles in the generation of pacemaker activities. Changes in the physiological conditions of the fish that are triggered by environmental, pheromonal, hormonal factors, etc., probably act on the modulator neurons via hormones and/or neurotransmitters. The properties of the ionic channels that underlie pacemaker activities of modulator neurons may be modified by some kind of signal transduction mechanisms. This will result in the ability of modulator neurons to alter their own pacemaker frequencies or to switch among different discharge modes. In other words, the animal's physiological conditions may be encoded in the frequency and/or pattern of discharge of modulator neurons. These modulator neurons, in turn, can regulate simultaneously the excitability of target neurons in a wide variety of brain regions via extensive, multiple axonal branches. Less