Novel mouse IgG-like immunoreactivity expressed by neurons in the moth Manduca sexta: Developmental regulation and colocalization with crustacean cardioactive peptide

Immunoglobulin-related molecules have been shown to play important roles in cell-cell recognition events during the development of both vertebrate and invertebrate nervous systems. In the moth, Manduca sexta, we report the presence of novel, mouse, immunoglobulin G (mIgG)-like immunoreactivity in a discrete population of identified neurosecretory neurons (the NS-Ls also known as the cell 27s) and interneurons (the IN-704s). A number of polyclonal anti-mIgG antibodies were used to immunostain these cells in wholemount. The mIgG-like-immunoreactive (IR) neurons were present during embryogenesis through the developing adult stages, but disappeared in the postemerged adult. Biochemical analysis of M. sexta ventral nerve cords revealed that the mIgG-like antigen is a membrane-associated 27-kDa protein which is likely responsible for the mIgG-like immunostaining observed. Unambiguous identification of the mIgG-like-IR neurons was based on neuronal morphology and our ability to demonstrate conclusively that these neurons expressed immunoreactivity to an antiserum against crustacean cardioactive peptide (CCAP). The NS-Ls and IN-704s were both shown to colocalize the CCAP and mIgG-like immunoreactivities. The mIgG-like and CCAP-IR neurons were identical to a subset of CCAP-IR neurons recently described by Davis et al. [(1993) J. Comp. Neurol., 338:612-627] in pupae. We found these CCAP-IR neurons, however, also to be present in larvae. The mIgG-like- and CCAP-IR neurons included the NS-L pair of the subesophageal maxillary neuromere, which projected anteriorly to the corpora cardiaca, and the NS-L of the labial neuromere whose axons projected out the dorsal nerve of the next posterior ganglion. The mIgG-like and CCAP-IR NS-Ls were also observed throughout the three thoracic ganglia, and all shared strikingly similar structural features. These cells exited out the dorsal nerve of the next posterior ganglion and eventually projected to the neurohemal release sites of the perivisceral organs. These neurons appear to be the homologues of the abdominal CCAP-IR NS-Ls, neurons that in the adult switch their neurotransmitter and release the neuropeptide bursicon. Our description of the distribution and developmental expression of this novel mIgG-like immunoreactivity may provide new insights into the regulation of neurotransmitter plasticity and/or recognition-signaling events involved in the embryonic and postembryonic assembly of the nervous system.