Mayeri E
Fed Proc. 1979 Jun;38(7):2103-8.
The abdominal ganglion of Aplysia provides a convenient experimental system for cellular studies on the roles of peptides as chemical messengers in the nervous system. There are indications that the bag cells, a group of neuroendocrine cells, synthesize and release egg laying hormone (ELH), a peptide with an apparent molecular weight of 6000. Our recent investigations indicate that a burst of impulse activity in the bag cells produces five types of long-lasting responses, some excitatory, others inhibitory, in 26 identified neurons and 2 identified cell clusters located near the bag cells in the abdominal ganglion. The responses have slow, smoothly graded onsets, and many of them result in modulation of neuronal activity for 3 hours or more. Physiological and ultrastructural data support the hypothesis that they are induced by a bag cell hormone (or hormones) that is released into vascular and interstitial spaces of the ganglion to act on the target neurons. Local application of purified ELH to one of the target neurons provides evidence that the bag cell effect is mediated by ELH. Many of the target neurons are known to be parts of neuronal circuits that control specific behavioral and homeostatic processes. Since egg laying is initiated by the bag cell discharge and is associated with a stereotyped behavior pattern lasting several hours, the actions of these peptide-secreting neurons on the central nervous system may serve to regulate certain elements of behavior and homeostasis during egg laying.
海兔的腹神经节为研究肽作为神经系统化学信使的作用提供了一个便利的实验系统。有迹象表明，袋状细胞是一群神经内分泌细胞，它们合成并释放产卵激素（ELH），这是一种表观分子量为6000的肽。我们最近的研究表明，袋状细胞中一阵冲动活动会在腹神经节中位于袋状细胞附近的26个已鉴定神经元和2个已鉴定细胞簇中产生五种类型的持久反应，有些是兴奋性的，有些是抑制性的。这些反应起始缓慢、逐渐分级，并且其中许多会导致神经元活动调制持续3小时或更长时间。生理学和超微结构数据支持这样的假设，即它们是由释放到神经节血管和间质空间中作用于靶神经元的一种或多种袋状细胞激素诱导的。将纯化的ELH局部应用于其中一个靶神经元，为袋状细胞效应由ELH介导提供了证据。许多靶神经元已知是控制特定行为和稳态过程的神经回路的一部分。由于产卵由袋状细胞放电引发，并与持续数小时的刻板行为模式相关，这些分泌肽的神经元对中枢神经系统的作用可能在产卵过程中调节行为和稳态的某些要素。
