Neuronal circuitry and nerve terminals regulating the sacral parasympathetic preganglionic neurons

点击翻译按钮获取中文摘要

To clarify the neural regulation to parasympathetic preganglionic neurons, nerve fibers and terminals distributing around sacral preganglionic neurons of the rat were investigated by using immunohistochemistry combined with axonal racing and nerve transection experiments, and the following results were obtained.1. About 50-60% of the sacral preganglionic neurons were immunoreactive for NO synthase.2-1). In the sacral spinal cord, substance P (SP)-, calcitonin gene-related peptide (CGRP)-, vesicular acetylcholine transporter (VAChT)-, and vasoactive intestinal polypeptide (VIP)-immunoreactive fibers extending from Lissauer's tract along the lateral edge of the dorsal horn to the autonomic nucleus were found, and fibers immunoreactive for SP and CGRP formed a dense networks of nerve terminals around the preganglionic cells.2). Although, both lumbar and sacral preganglionic neurons received enkephalin (ENK)-immunoreactive nerve fibers from the dorsal central gray, ENK fibers in the sacral … More spinal cord also contained neuropeptide Y (NPY) and formed nerve terminals mainly distributing outside of the CGRP/SP nerve networks.3). Lumbar sympathetic preganglionic neurons received many serotonin (5-HT)- and tyrosine hydroxylase (TH)-immunoreactive descending fibers. In contrast, 5-HT and TH fibers around sacral preganglionic neurons were scarce and. Did not showed selective distribution.3. These fibers did not disappear after the transection of the L4, L5 spinal cord, suggesting that they are of intrinsic or of peripheral origin.4. Transection experiments of the spinal nerve revealed that VAChT, VIP, SP and CGRP fibers were of peripheral origin, and VAChT and VIP fibers came from the myenteric neurons in the most distal potion of the rectum.5. In the pelvic visceral sensory system, the expression of vanilloid reception 1 (VR1) was restricted to the afferents from the ureter and fundus of urinary bladder, the superficial dorsal horn and fibers in the lateral collateral pathway extending along the lateral edge of the dorsal horn into the parasympathetic preganglionic nucleus, suggesting that these VR1-positve afferents were involved in regulation of the sacral preganglionic neurons. Less