Submitted to: Microscopy Research and Technique
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/1994
Publication Date: N/A
Interpretive Summary: Insects use chemicals called neuropeptides to control many aspects of growth, development and behavior. Although the structure of many neuropeptides is known, the sites in which they are produced and the way that they travel to the organs on which they act is poorly understood. Understanding these features is critical to determining how neuropeptides act. An international team of scientists, including researchers at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville Florida have been studying the neuroendocrine system of the tobacco hawkmoth. Their research has been instrumental in determining the parts of the insect brain that produce several neuropeptides and the specific nerves used to transport the neuropeptides to different parts of the insect. Their research has documented that many neuropeptides are produced by the same areas of the brain and are delivered by the same nerves. This information has clarified many questions about how neuropeptides function and has provided information that is critical for development of novel techniques of pest insect control utilizing neuropeptides.
Technical Abstract: The median neuroendocrine cells of the subesophageal ganglion, important components of the neuroendocrine system of the tobacco hawkmoth, Manduca sexta, have not been well investigated. Therefore, we studied the anatomy of these cells by axonal backfills and characterized their peptide immunoreactivities. Processes of the median neuroendocrine cells project to terminations in the corpora cardiaca via the third and the ventral nerves of this neuro-hemal organ, but the ventral nerve of the corpus cardiacum is the principal neurohemal surface for this system. Cobalt backfills of the third cardiacal nerves revealed lateral cells in the maxillary neuromere and a ventro-median pair in the labial neuromere. Backfills of the ventral cardiacal nerves revealed two ventro-median pairs of cells in the mandibular neuromere and two ventro-median triplets in the maxillary neuromere. The efferent projections of these cells are contralateral. The three sets of median neuroendocrine cells are PBAN- and FMRFamide-immunoreactive, but only the mandibular and maxillary cells are proctolin-immunoreactive. Characteristics of EMRFamide-like immunostaining suggest that the median neuroendocrine cells may contain 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. Two pairs of interneurons immunologically related to the neurosecretory cells are associated with the median maxillary neuroendocrine cells. These cells are PBAN-, FMRFamide-, SCP-, and sulfakinin-immunoreactive and project to arborizations in the brain and all ventral ganglia.