Cholinergic neurons of the pelvic autonomic ganglia and uterus of the female rat: distribution of axons and presence of muscarinic receptors

Acetylcholine (ACh) stimulates contraction of the uterus and dilates the ut erine arterial supply. Uterine cholinergic nerves arise from the paracervic al ganglia and were, in the past, characterized based on acetylcholinestera se (AChE) histochemistry, However, the histochemical reaction for acetylcho linesterase provides only indirect evidence of acetylcholine location and i s a nonspecific marker for cholinergic nerves. The present study: (1) reeva luated cholinergic neurons of the paracervical ganglia, (2) examined the ch olinergic innervation of the uterus by using retrograde axonal tracing and antibodies against molecules specific to cholinergic neurons, choline acety ltransferase and the vesicular acetylcholine transporter, and (3) examined muscarinic receptors in the paracervical ganglia using autoradiography and a radiolabeled agonist. Most ganglionic neurons were choline acetyltransfer ase- and vesicular acetylcholine transporter-immunoreactive and were appose d by choline acetyltransferase/vesicular acetylcholine transporter-immunore active terminals. Retrograde tracing showed that some cholinergic neurons p rojected axons to the uterus. These nerves formed moderately dense plexuses in the myometrium, cervical smooth muscle and microarterial system of the uterine horns and cervix. Finally, the paracervical ganglia contain muscari nic receptors. These results clearly reveal the cholinergic innervation of the uterus and cervix, a source of these nerves, and demonstrate the muscar inic receptor content of the paracervical ganglia. Cholinergic nerves could play significant roles in the control of uterine myometrium and vasculatur e.