Neuronal gastrin-releasing peptide in the mammalian gut and pancreas.

Immunoreactive gastrin releasing peptide (GRP) was demonstrated in neuronal elements in the porcine pancreas and in the gut of several mammals. Immunoreactive endocrine cells could not be detected. The results of radioimmunochemical analysis agreed well with those of immunocytochemistry. The occurrence of gastrin-releasing peptide-containing nerve cell bodies in the myenteric ganglia all along the gut indicates that gastrin-releasing peptide fibers are intramural in origin. The distribution of gastrin-releasing peptide fibers in all layers of the gut wall suggests multiple functions of gastrin-releasing peptide, including a role in the regulation of intramural neuronal activities, smooth muscle tone and in secretory and absorptive processes.