DISTRIBUTION AND SEASONAL-VARIATION OF VASOACTIVE INTESTINAL (VIP)-LIKE PEPTIDES IN THE NERVOUS-SYSTEM OF HELIX-POMATIA

The distribution of neuropeptides immunologically related to vasoactiv e intestinal peptide (VIP) and its precursor peptide preproVIP(111-122 ), as well as to other peptides of the VIP-family, was studied in the central and peripheral nervous and sensory system of the snail, Helix pomatia, by use of immunocytochemical methods. VIP and preproVIP immun oreactivity was present in somata and nerve fibres of all central gang lia. Hibernating snails contained on average a total of 670 VIP- and 7 63 preproVIP-immunoreactive. neurons. The number of immunoreactive cel ls was substantially reduced by more than 50% in active snails during summer with an average of 289 VIP- and 356 preproVIP-immunoreactive ne urons. Antiserum against VIP labelled nerve fibres next to blood vesse ls and smooth muscle cells, whereas preproVIP-like material was locali zed in nerve fibres and endocrine-lice cells among dorsal body cells a nd in the connective tissue along fiber tracts. VIP-immunoreactive mat erial was also found in accessory ganglia of small and large tentacles , ganglia of the lips, the sensory epithelium of the tentacles, free n erve endings between skin epithelial cells, neuronal cells in the reti na and in the sensory epithelium of statocysts. The cell-specific dist ribution and the seasonal variation of VIP- and preproVIP-like peptide s suggest that they may act as transmitters or modulators in the nervo us and sensory system and may be involved in the physiological adaptat ion of central neurons during long-term resting periods of snails.