Localization and Kinetics of Neural Transmitters in the Enteric Nervous System. Studies Using Laser Photoooagulations and Immunochemistry.

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We investigated nerve regeneration. following lesion forming Argon ion laser irradiation in the guinea-pig small intestine by immunohistochemistry using peroxidase-antiperoxidase complex techniques over a time course of up to 70 days.Round laser-lesions about 0.5mm in diameter were produced and the regenerative features of the two major cell types of the enteric nerve plexuses. i.e. enteric neurons containing neuropeptide by such as methionine-enkephalin-Arg^6-Gly^7-Leu^8 (Enk^<-8>).Peptide-hisbydine-isoleucine (PIII). substance P (SP) and somatostatin (SM) together with tby enteric glial cells containing nerve tissue protein S 100b (S-100b protein by were examined.Immediately after the laser irradiation. the histological structure of the enteric nerve plexuses remained almost intact. though both neuronal and glial cells were coagulated and dead. The immunoreactivities for neuropeptides and S-100b proteins in the neuronal and glial elements respectively were also mostly preserved. By 3 … More hrs after the laser irradiatio, a conspicuous accumulation of immunoreactivities to neuropeptides occurred in the severed nerve stumps. The cellular debris, containing neuropeptides/S-100b protein, were gradually removed from the lesion by 3 days. Since neuropeptides in the neuronal processes are transported from the cell body by the fast anterograde axonal flow, an early accumulation of neuropeptides on the oral edge of the lesion indicates that the neurons project processes in the oro-anal direction, and vice versa.It was deduced that, in the myenteric plexus, both Enk-8 and SP neurons issued both orally and anally directed processes; whereas, PHI and SM neurons sent processes mainly in the oro-anal direct-ion. In the deep muscular plexus (DMP), Enk-8 and SP neurons ran circularly. In the submucous plexus, projections of PHI, SP and SM neurons were directed evenly in all directions.Neuropeptide immunoreactivities of the axotomized nerve cell bodies in the area surrounding the lesion became strikingly stronger 3 to 10 days after laser irradiation. This phenomenon was interpreted as a mode of retrograde degeneration of the enteric neurons. At 15 to 70 days, regenerated nerve plekuses completely spread over the scar tissue of the laser lesion. No nerve cell body, however, existed in the lesioned ganglia. In the regenerated nerve plexus, the glial cells, which proliferated by mitosis, supported and guided the nerve fibers which extended from the survived neuronal cell bodies in the ganglia around the lesion. This suggests that the characteristic neuron/glial cell interactions in the laser lesion might also occur daring the continuous remodeling of the autonomic groundplexus under non-experimental conditions in the enteric nerve plexuses. Less