Sensory innervation of the external genital tract of female guinea pigs and mice.

INTRODUCTION: The structural and neurochemical characterization of the sensory innervation of the external genitalia of females is poorly known. AIMS: To immunohistochemically map the sensory innervation of external genitalia and surrounding structures of female guinea pigs and mice. METHODS: Large-diameter sensory fibers, presumably mechanoreceptors, were identified by their immunoreactivity to neuron-specific enolase (NSE) or vesicular glutamate transporter 1 (VGluT1). Peptidergic sensory fibers, presumably unmyelinated nociceptors, were identified by their immunoreactivity to calcitonin gene-related peptide (CGRP), substance P, or both. Multiple-labelled tissues were examined with high-resolution confocal microscopy. MAIN OUTCOME MEASURES: Microscopic identification of sensory endings, including potential nociceptors, characteristic of the external genitalia. RESULTS: Large complex nerve endings immunoreactive for NSE and VGluT1 were abundant in dermal papillae of the clitoris. Each large ending was accompanied by one or two fine fibers immunoreactive for CGRP but neither substance P nor VGluT1. More simple NSE-immunoreactive endings occurred within dermal papillae in non-hairy skin of the labia and anal canal but were rare in pudendal or perineal hairy skin. Fine intra-epithelial fibers immunoreactive for NSE but not CGRP were abundant in hairy skin but rare in non-hairy genital skin and the clitoris. Only fine varicose fibers immunoreactive for both CGRP and substance P occurred in connective tissue underlying the mucosal epithelium of cervix and endometrium. CONCLUSION: Compared with surrounding tissues, the sensory innervation of the clitoris is highly specialized. The coactivation of nociceptors containing CGRP but not substance P within each mechanoreceptor complex could be the explanation of pain disorders of the external genitalia.

Sacro-lumbar intersegmental spinal reflex in autonomic pathways mediating female sexual function.

INTRODUCTION: Autonomic neurons in paracervical ganglia mediating vasodilation in the female reproductive tract receive inputs from both midlumbar and sacral spinal levels. However, it is not known how the lumbar pathways are activated. AIM: This study tested whether stimulation of pudendal sensory nerve could activate lumbar spinal outflows to paracervical ganglia via a spinal reflex pathway. METHODS: Isolated spinal cords with attached peripheral nerves were removed from urethane-anesthetized female guinea pigs and perfused via the aorta with physiological salt solution. Spinal pathways to midlumbar preganglionic neurons were tested by recording extracellular compound action potentials (CAPs) in lumbar splanchnic or distal hypogastric nerves after electrical stimulation of thoracic spinal cord or the pudendal nerve. CAPs also were recorded from pelvic nerves after pudendal nerve stimulation. Sensory neurons were retrogradely traced from the pudendal nerve and characterized immunohistochemically. MAIN OUTCOME MEASURES: Activation of preganglionic neurons projecting from midlumbar spinal cord to paracervical ganglia following stimulation of pudendal sensory nerves in isolated preparations. RESULTS: Thoracic spinal cord stimulation produced CAPs in hypogastric nerves that were abolished by transection of L3 lumbar splanchnic nerves. Pudendal nerve stimulation produced CAPs in L3 lumbar splanchnic, hypogastric, and pelvic nerves, demonstrating an ascending intersegmental spinal circuit to midlumbar levels in addition to the sacral spinal circuit. These CAPs in hypogastric nerves were enhanced by bicuculline (10 µM), blocked by tetrodotoxin (1 µM) but were not affected by hexamethonium (200 µM). Retrograde axonal tracing revealed four groups of sensory neurons in S3 dorsal root ganglia that were distinguished immunohistochemically. CONCLUSION: Midlumbar preganglionic neurons projecting to paracervical ganglia regulating blood flow and motility in the female reproductive tract can be activated by an ascending intersegmental spinal pathway from pudendal sacral inputs, which is inhibited by local spinal circuits. This pathway will help understand pathological conditions affecting reproductive function.

Congestion control for ATM multiplexers using neural networks: multiple sources/single buffer scenario.

A new neural network based method for solving the problem of congestion control arising at the user network interface (UNI) of ATM networks is proposed in this paper. Unlike the previous methods where the coding rate for all traffic sources as controller output signals is tuned in a body, the proposed method adjusts the coding rate for only a part of the traffic sources while the remainder sources send the cells in the previous coding rate in case of occurrence of congestion. The controller output signals include the source coding rate and the percentage of the sources that send cells at the corresponding coding rate. The control methods not only minimize the cell loss rate but also guarantee the quality of information (such as voice sources) fed into the multiplexer buffer. Simulations with 150 ADPCM voice sources fed into the multiplexer buffer showed that the proposed methods have advantage over the previous methods in the aspect of the performance indices such as cell loss rate (CLR) and voice quality.