The distribution of putative neurotransmitters in the nervous system of the dipteran Chironomus tentans insect larva: An immunohistochemical study using antisera to 5-hydroxytryptamine, tyrosine hydroxylase, methionine-enkephalin, proctolin and bombesin.

Abstract Using the indirect immunofluorescence technique, the localization and distribution of transmitters, transmitter-related enzymes and neuropeptides was studied in the larvae of the dipteran species Chironomus tentans . Immunoreactivity could be seen for 5-hydroxytryptamine, tyrosine hydroxylase (the rate-limiting enzyme in the catecholamine synthesis), and the neuropeptides methionine-enkephalin (met-enk), proctolin and bombesin. The immunoreactivity was confined both to cell bodies as well as to nerve fibers within ganglia and along the alimentary canal. Furthermore, tyrosine hydroxylase immunoreactivity could also be seen in epithelial cells locally distributed along a short, middle part of the alimentary tract. These latter cells were regarded as endocrine-like cells. No immunoreactivity could be found with certainty for the enzyme phenylethanolamine- N -methyltransferase (PNMT) nor for the peptides vasoactive intestinal polypeptide (VIP), dynorphin, substance P, somatostatin, thyrotropin releasing hormone (TRH), neuropeptide Y (NPY), peptide histidine isoleucine amide (PHI), neurotensin, galanin and cholecystokinin (CCK).