Characterisation of multiple immunoreactive neurons in the central nervous system of the pond snail Lymnaea stagnalis with different fixatives and antisera adsorbed with the homologous and the heterologous antigens.

In the central nervous system of the pond snail Lymnaea stagnalis a large number of elements (cells and fibers) can be identified with antisera (a-FM) to the molluscan cardioactive tetrapeptide FMRFamide (Phe-Met-Arg-Phe-NH2). Of these elements some are also reactive to antivasotocin (a-VT) and/or anti-gastrin (a-Gas). These observations suggest that the a-FM positive elements belong to more than one type. Previous results had already indicated that the immunoreactivity of many a-FM positive cells is influenced by the type of fixation. Taking into account the effects of three fixatives on the reactivity of the cells, and their staining characteristics with the two other antisera used, 8 a-FM positive types could be distinguished. Homologous and heterologous adsorptions were carried out to test the specificity of a-FM, a-VT and a-Gas. After homologous adsorptions no staining was obtained. After heterologous adsorptions only part of the multiple staining cells were identified. This indicates that in a-FM, a-VT and a-Gas in addition to (more) selective IgG molecules, less specific IgG molecules occur that can bind to other peptides than those used to raise the antisera (cross-reaction). The (more) selective IgG molecules in a-FM bind to 6 of the a-FM positive types, suggesting that in L. stagnalis a family of FMRFamide-like substances occurs. This conclusion is sustained by results obtained with a-FM adsorbed with fragments of FMRFamide.(ABSTRACT TRUNCATED AT 250 WORDS)