Morphological study of the submucosal and mucosal plexuses of the sheep forestomach.

Submucosal and mucosal nerve plexuses in the ovine forestomach were examined by immunohistochemical staining for protein gene-product 9.5 (PGP 9.5) and for S-100 protein (S-100), using whole-mount specimens that had been prepared by treatment with KOH. Nerve fibers of various sizes and glial cells (i.e., Schwann cells and satellite cells) were stained with antibodies against PGP 9.5 and S-100 respectively. The network of the submucosal plexus in the rumen is irregular and some nerve bundles in the plexus cross over other bundles. Some of the nerve bundles penetrate the ruminal papillae. The submucosal plexus in the reticulum consists of a network in the reticular wall and the reticular folds. The submucosal plexus in the omasum is also divided into two segments; namely, the sublaminar and the intralaminar plexuses. Most of the submucosal ganglion cells are unipolar and smooth-surfaced, being located singly or in small groups. A few perikarya were detected in the ruminal papillae. The number of perikarya per unit surface area is greater in the caudal portion of the omasal lamina (19.32 +/- 8.62 per cm2). In the mucosal plexuses, a well-developed network of beaded fibers with PGP 9.5-like immunoreactivity and a glial framework of S-100 like immunoreactivity was observed, in particular in the ruminal, reticular and omasal papillae. The intrapapillary nervous networks are interconnected by thin bundles of nerves in the interpapillary region. The present results suggest that some of the mucosal functions are intrinsically regulated by the submucosal and mucosal plexuses in the ovine forestomach.