Intrinsic nerve fibers of the primate endometrium

An experiment was designed to test the currently favored theory that inasmuch as nerve fibers are undemonstrable in the outer glandular portion of the uterine mucosa certain endometrial functions must be regulated solely by humoral mechanisms. Searches ordinarily have been confined to tissues removed surgically which have begun to undergo post-mortem changes. A methylene-blue intravital staining method, quite specific for fine peripheral nerve fibers, was used in five anesthetized cats, a guinea pig, and three monkeys; injections of the dye solution were made directly into the superficial glandular layer of the living endometrium. Similar injections were made in pieces of endometrium that had been removed surgically 5 to 10 min previously. Fine nerve fibers were found in all instances, but they stained more sharply and deeply after intravital injections. The presence of neurons in a region usually considered to be exclusively under humoral control may require modifications of current theories. In species that menstruate, the endometrial nerve fibers probably undergo cyclical degeneration and regeneration physiologically.