TACHYKININ-RELATED AND LEUCOKININ-RELATED PEPTIDES IN THE MOLLUSCAN NERVOUS-SYSTEM

Distribution of locustatachykinin-like immunoreactive (LomTKLI) and le ucokinin-like immunoreactive (LKLI) neurons in the central nervous sys tem (CNS) of the pond snail, Lymnaea stagnalis was investigated and co mpared to that found in Helix pomatia. Occurrence of LomTKLI neurons i n different ganglia of the freshwater bivalve, Anodonta cygnea, was al so studied. Similar to Helix, the Lymnaea CNS contained LomTKLI and LK LI neurons mainly in the cerebral and pedal ganglia, but the number of labelled neurons was found to be significantly lower in Lymnaea (150- 184 LomTKLI and 86-104 LKLI neurons). LomTKLI elements in Anodonta gan glia were mainly confined to the neuropil, whereas the immunostained p erikarya were only randomly distributed. LomTKLI and LKLI neurons were also demonstrated in a similar pattern of distribution in the intesti ne of Lymnaea and Helix. Analyzing the membrane effects of lacustatach ykinin-I, leucokinin-I and anodontatachykinin, Helix neurons were foun d to be either depolarized or hyperpolarized. Voltage-clamp experiment s revealed the role of Ca- or K-currents in peptide effects. Our resul ts indicate that the different tachykinin- and leucokinin-systems are involved in different central and peripheral regulatory processes of t he molluscan nervous system.