Myenteric enkephalin neurons around the laser-photocoagulation necrosis: an immunocytochemical investigation in the guinea pig jejunum and proximal colon.

Laser irradiation-caused features of neuronal regrowth containing enkephalin-like immunoreactivity in the myenteric plexus around the necrosis were investigated in the guinea pig jejunum and proximal colon using an antiserum to methionine-enkephalin-Arg6-Gly7-Leu8. The power level and irradiation time of the argon laser beam were adjusted to make a coagulation spot of about 0.5 mm in diameter. A distinct accumulation of the immunoreactivity occurred in the laser photocoagulated ends of the enkephalin neuron processes. Regeneration of the severed axon-like process took place in the following order: swelling and budding at the severed proximal end; elongation and branching of newly-formed nerve fibers; and formation of a tangled overgrowth. Approximately 43-90 hrs after the laser microsurgery, immunoreaction of the enkephalin neuron perikarya was stronger in the first several rows of ganglia, on both the oral and anal sides of the laser necrosis. In the jejunum, an increase in the intensity of the immunoreaction was more prominent on the oral side than on the anal side, whereas the proximal colon displayed an opposite state. In the jejunum, the anally-directed axon-like process of the enkephalin neurons transported a larger amount of the immunoreactivity as compared with the orally-directed wing-ramuli. This paper seeks to prove that the laser irradiation combined with immunocytochemistry may provide a simple and reliable methodology for the study of the projections of enteric neurons.