Structural studies of innervation on nonpregnant rat uterus

Whole-mount preparations of the uterus and mesentery from nonpregnant rats were examined after staining with glyoxylic acid or acetylcholinesterase to demonstrate the innervation. Some uterine tissues were also evaluated by electron microscopy. Glyoxylic acid fluorescent nerves were present in the mesentery, mesometrium, and uterine wall exclusively around blood vessels. Acetylcholinesterase positive nerve fibers from Frankenhäuser's plexus (cervical ganglia) were associated with blood vessels and muscle in the uterine wall but not in the mesentery. Electron microscopy revealed nerve varicosities with granular vesicles associated with blood vessels and varicosities with agranular vesicles located near blood vessels and muscle cells. Treatment of animals for 3 days with 5- and 6-hydroxydopamine, respectively, increased granular size and damaged the varicosities with granular vesicles but did not change nerves with agranular vesicles or induce the presence of gap junctions. The results of this study suggest that blood vessels in the uterus are highly innervated by both adrenergic and other types of nerves that probably control blood flow. Nonadrenergic but not adrenergic nerves may also directly control myometrial contractility.