Vagus nerve-uterus connections in the rat

Autonomic and sensory nerves supply the vasculature, epithelium and myometrium of the uterus. These fibers course in the pelvic and hypogastric nerves. However, recent physiological and behavioral data suggests the vagus nerves also supply the uterus and serve as additional routes for uterine information to reach the CNS. This study tested for anatomical connections between uterus and vagal sensory neurons in the nodose ganglia. Retrograde axonal tracing was performed using Fluorogold injected into the uterine cervix, body and horns; rats survived for 10-21 days to allow transport of the tracer. Other rats received nerve transactions to examine loss/degeneration of nerves from selected sources. Rats had either a bilateral pelvic neuroectomy (BLPN), hypogastric neuroectomy (HN) or abdominal vagotomy (AV), or various combinations of these neurectomies. In addition rats with neurectomies and/or high spinal cord transections received vaginocervical mechanical stimulation (VCS) to examine functional connections (via expression of the immediate early gene c-fos) in the nucleus tractus soliterius. Finally, sections of the nodose ganglia were immunostainsd to test for estrogen receptors (ER) in vagal neurons. Fluorogold-labeled and ER neurons were seen in sections of the nodose ganglia. AV reduced the number of fibers supplying the uterus in rats with BLPN+HN. VCS induced expression of Fos in the nucleus tractus solitarius. These data indicate a vagal input to the uterus and that these neurons may be responsive to estrogens. Such connections could be an additional route for uterine information to reach the brain in spinal cord-injured individuals.