TRANSMITTER IDENTIFICATION IN NEURONS INVOLVED IN MALE COPULATION BEHAVIOR IN LYMNAEA-STAGNALIS

In this paper, we have mapped the cellular localization of various tra nsmitters onto the central neurons which are involved in male copulati on behavior in Lymnaea stagnalis, by combining retrograde tracing with immunocytochemistry and in situ hybridization. Evidence is provided t hat neurons which were backfilled from the penis nerve, the sole nerve to innervate the male copulatory organ, synthesize a multitude of neu ropeptides (APGWamide, Lymnaea neuropeptide tyrosin [LNPY], conopressi n, pedal peptide, SEEPLY, DEILSR, myomodulin, and Lymnaea inhibitory p eptide [LIP]) as well as the classical neurotransmitter, serotonin. In the anterior lobe, the backfilled neurons mainly contain the tetrapep tide APGWamide and conopressin, and not LNPY or pedal peptide. The res ults suggest a central role in the regulation of copulation activity f or the anterior lobe neurons that; produce APGWamide and conopressin. Immunostainings of backfilled nervous systems revealed immunopositive axons originating from these neurons to form varicosities on the cell somata of neurons in the other clusters contributing to the innervatio n of the male sexual system. Neurons from the right parietal ganglion projecting into the penis nerve were electrophysiologically and morpho logically identified by simultaneously recording from the cell body in tracellularly and the penis nerve extracellularly and subsequently fil ling them with an anterograde tracer and subjecting them to immunocyto chemistry. This method has provided links between morphology, physiolo gy, and the transmitter contents of these neurons. (C) 1998 Wiley-Liss , Inc.