PREGANGLIONIC FIBERS IN THE RAT HYPOGASTRIC NERVE PROJECT BILATERALLYTO PELVIC GANGLIA

Stimulation of the hypogastric nerve (HGN) often evokes bilateral resp onses in some pelvic organs. Retrograde labeling studies indicate that axons of postganglionic neurons often cross to the opposite side. How ever, there is little information available as to whether preganglioni c fibers in the HGN have a contralateral projection to pelvic ganglia. A retrograde tracer was injected into the left major pelvic ganglion (MPG) in rats receiving various lesions of preganglionic nerves (HGN a nd pelvic nerve, PN). The lumbar spinal cord was then examined for loc ation and number of dye-filled neurons. In a second approach, the inci dence of synaptophysin immunoreactivity (SN-IR) perineuronal profiles (baskets) was examined in the MPG and in the accessory pelvic ganglia (APG) after nerve lesions. Labeled neuronal profiles were found in spi nal cord nuclei (Lumbar(1-2)) after dye injection of the MPG in animal s with an intact contralateral HGN. Cutting both HGNs virtually elimin ated dye labeling in the lumbar cord, as did severing commissural bran ches (CB) between pelvic ganglia (leaving the contralateral HGN intact ). Some SN-IR baskets were found in the left APG when only the contral ateral HGN was intact, but baskets were rare when all four preganglion ic nerves were cut. It could not be determined whether the HGN project s to the contralateral MPG, since SN-IR baskets were numerous in the M PG even when all four nerves were cut. This study has shown that some preganglionic fibers in the HGN synapse on neurons in contralateral pe lvic ganglia. Both the APG and MPG receive contralateral innervation, but it is likely that neurons in the APG are the primary target of thi s input. Thus, in addition to crossing postganglionic fibers, a portio n of the bilateral control of pelvic tissues is accomplished by pregan glionic fibers which target autonomic neurons in contralateral ganglia . Anat. Rec. 252:229-234, 1998. (C) 1998 Wiley-Liss, Inc.