Excitability and branching of neuroendocrine cells during reproductive senescence

In the mollusc Lymnaea stagnalis, neuroendocrine caudodorsal cells (CDCs) w ere studied physiologically and morphologically from egg layers (EL) (aged 154-400), and animals 4 weeks (CEL-Lt) (342-455 days), and 8 weeks (CEL-g) (477-660 days) after production of their last egg mass. After recording che mical transmission, electrical coupling and stimulation induced afterdischa rges (ADs), CDCs then were filled with Lucifer Yellow. Based on the axonal branching revealed by Lucifer Yellow, CDCs were classified as extensively, moderately, or minimally branched. In EL-CDCs, induction of AD activity, wh ich normally (9) precedes egg-laying, only was initiated in the resting sta te. CEL-4 CDCs exhibited ADs whereas CEL-8 CDCs did nor. CEL-8 CDCs exhibit ed significantly reduced chemical and electrical transmission, and CEL-4 CD Cs did not differ from resting state EL-CDCs. CDC branching was significant ly reduced with both increasing age and declining egg-laying. Minimally bra nched CDCs most frequently failed to exhibit an AD and exhibited reduced el ectrical coupling. We conclude that both physiology and morphology of CDCs are related to age and reproductive state. (C) 2000 Elsevier Science Inc. A ll rights reserved.