GASTRIN-CHOLECYSTOKININ-LIKE IMMUNOREACTIVITY IN THE CENTRAL-NERVOUS-SYSTEM OF THE MILKWEED BUG, SPILOSTETHUS-PANDURUS - ULTRASTRUCTURAL ASPECTS OF THE REACTIVE A-CELLS OF THE BRAIN

All the ganglia belonging to the central nervous system of adults of t he milkweed bug Spilostethus pandurus (Hemiptera) were screened immuno histochemically for vertebrate gastrin-cholecystokinin (CCK-8(s))-like peptides. Several large reactive perikarya are present in the median part of the protocerebrum, their processes extending to the dorsal 'ao rta'. These cell bodies are also paraldehyde fuchsin-positive, ie they are A-type cells. in the lateral part of the protocerebrum, in the de utocerebrum and tritocerebrum, and in the suboesophageal, prothoracic and abdominal ganglia, a few immunoreactive cell bodies send axonal pr ocesses into their respective neuropiles. The A-type cells reactive to CCK antiserum were identified, at the ultrastructural level, by combi ning paraldehyde fuschin staining of semithin sections with a post-emb edding immunogold technique carried out on adjacent ultrathin sections . The neurosecretory cells contain numerous vesicles of elevated elect ron density. These data suggest that members of the CCK peptide family are present in the central nervous system of Spilostethus pandurus.