Immunocytochemical demonstration of peptidergic neurons in the central nervous system of the pond snail Lymnaea stagnalis with antisera raised to biologically active peptides of vertebrates

Perikarya and nerve fibers were immunocytochemically identified in the central nervous system of the pond snail Lymnaea stagnalis by means of the unlabelled antibody enzyme method with antisera to 15 biologically active peptides of vertebrates: vasopressin, vasotocin, oxytocin, α-melanocyte stimulating hormone (α-MSH), met-enkephalin, somatostatin, glucagon, insulin, glucose-dependent insulinotropic peptide (GIP), vaso-active intestinal polypeptide (VIP), gastrin, secretin, pancreatic polypeptide (PP), Substance P, calcitonin. No immunostaining was obtained with antisera to β-endorphin, cholecystokinin (CCK), neurophysin I and II. Particular neurons could be identified with two antisera (anti-vasopressin/vasotocin, anti-α-MSH/metenkephalin, anti-substance P/PP, anti-PP/gastrin). Apparently this indicates that populations of cells identified with a given antiserum may consist of more than one cell type.