NEUROANATOMY AND IMMUNOCYTOCHEMISTRY OF THE MEDIAN NEUROENDOCRINE CELLS OF THE SUBESOPHAGEAL GANGLION OF THE TOBACCO HAWKMOTH, MANDUCA-SEXTA - IMMUNOREACTIVITIES TO PBAN AND OTHER NEUROPEPTIDES

The median neuroendocrine cells of the subesophageal ganglion, importa nt components of the neuroendocrine system of the tobacco hawkmoth, Ma nduca sexta, have not been well investigated. Therefore, we studied th e anatomy of these cells by axonal backfills and characterized their p eptide immunoreactivities. Both larvae and adults were examined, and d evelopmental changes in these neuroendocrine cells were followed. Proc esses of the median neuroendocrine cells project to terminations in th e corpora cardiaca via the third and the ventral nerves of this neuroh emal organ, but the ventral nerve of the corpus cardiacum is the princ ipal neurohemal surface for this system. Cobalt backfills of the third cardiacal nerves revealed lateral cells in the maxillary neuromere an d a ventro-median pair in the labial neuromere. Backfills of the ventr al cardiacal nerves revealed two ventro-median pairs of cells in the m andibular neuromere and two ventromedian triplets in the maxillary neu romere. The efferent projections of these cells are contralateral. The anatomy of the system is basically the same in larvae and adults. The three sets of median neuroendocrine cells are PBAN- and FMRFamide-imm unoreactive, but only the mandibular and maxillary cells are proctolin -immunoreactive. During metamorphosis, the mandibular and maxillary ce lls also acquire CCK-like immunoreactivity and the labial cells become SCP- and sulfakinin-immunoreactive. Characteristics of FMRFamide-like immunostaining suggest that the median neuroendocrine cells may conta in one or more of the FLRFamides that have been identified in M. sexta . The mandibular and maxillary neuroendocrine cells appear to produce the same set of hormones, and a somewhat different set of hormones is produced by the labial neuroendocrine cells. Two pairs of interneurons immunologically related to the neurosecretory cells are associated wi th the median maxillary neuroendocrine cells. These cells are PBAN-, F MRFamide-, SCP-, and sulfakinin-immunoreactive and project to arboriza tions in the brain and all ventral ganglia. These interneurons appear to have extensive modulatory functions in the CNS. (C) 1996 Wiley-Liss , Inc.