Information is sought to answer questions about the relationship between the differing electrical characteristics of neurons that secrete different peptide hormones and their biochemical and morphological characteristics. The neurons will be studied intact within an acutely isolated preparation and isolated in cell culture. In culture, the neurons synthesizing different hormones, as indicated by their immunoreactivity to specific antisera, assume distinct morphologies under defined conditions. The cultured neurons having different form show distinct differences in their electrical characteristics. The material used for these studies is the X-organ - sinus gland of the tropical land crab, Cardisoma carnifex. Earlier work has demonstrated that this crustacean neurosecretory system is directly analogous to the major vertebrate neurosecretory system, the hypothalamic-neurohypophyseal system, and that at every level of analysis yet undertaken the physiological and cell biological mechanisms involved are directly comparable. Many of the observations obtainable with the crab material, however, would not be possible with vertebrate material. The crab neurosecretory system is easily isolated and consists exclusively of peptidergic neurons and supporting tissue. The terminals are unusually large (up to 30um), permitting recording with intracellular or patch electrodes. Antisera to several peptide- hormonal activities permit typing of neurons and terminals. Isolated X-organ neurons immediately commence regeneration of processes in unconditioned dishes and defined media. Conventional microelectrode techniques and dye injection will be used to characterize neurons in acutely isolated systems. Both conventional and patch-clamping techniques will be applied to the neurons in culture. The regional distribution in the membrane of channels giving rise to different ionic currents will be explored by testing the effects of axotomy and by localized recording. Regional sensitivity to putative neurotransmitter agents will be explored. As feasible, changes with time in culture or with changed morphology induced by altered culturing conditions will be detailed.
