Abstract

The anatomical distribution of chromaffin paraganglia (PG) associated with the inferior mesenteric ganglion (lMG) in cats was defined initially by perfusing animals with a combined staining/ fixing solution containing potassium dichromate and glutaraldehyde. The dichromate component stained and distinctly mapped 3 to 6 chromaffin paraganglia that that were distributed randomly around the surface of each IMG. On the other hand, glutaraldehyde preserved the morphological integrity of the chromaffin organs for subsequent histological and ultrastructural evaluation. The IMG always appeared as a paired structure surrounding the inferior mesenteric artery (lMA). Elongated paraaortic chromaffin organs occurred ventral to the abdominal aorta in the midretropcritoneum. Histological evaluation showed that a paranglion was separated from the adjacent IMG by a vascular and connective tissue capsule. Large chromaffin cell clusters occurred within the IMG proper, but continuity between intraganglion and paraganglion chromaffin tissue was not evident. All chromaffin cells contained granules with dense cores and otherwise displayed features consist~nt with ~h~omaffin cells in general. Nerve endings containing clear vesicles established contact with the intraganglion chromaffin cells; however, terminals were never observed contacting the paraganglion or paraaortic chromaffin cells. This study shows clearly that a variable number of chromaffin paraganglia arc juxtapositioned to the IMG in cats, and that similar cells assimilate in clusters of considerable size within the IMG and alongside the abdominal aorta.