Characterizing the autonomic neural connections between the abdominal aortic and superior hypogastric plexuses: A multimodal neuroanatomical study

The aortic plexus serves as the primary gateway for sympathetic fibers innervating the pelvic viscera. Damage to this plexus and/or its associated branches can lead to an assortment of neurogenic complications such as bladder dysregulation or retrograde ejaculation. The neuroanatomy of this autonomic plexus has only recently been clarified in humans; as such, the precise function of its constituent fibers is still not clear. Further study into the functional neuroanatomy of the aortic plexus could help refine nerve-sparing surgical procedures that risk debilitating neurogenic complications, while also advancing understanding of peripheral sympathetic circuitry. To this end, the current study employed an in vivo electrostimulation paradigm in a porcine model, in combination with lipophilic neuronal tracing experiments in fixed, post-mortem human tissues, to further characterize the functional neuroanatomy of the aortic plexus. Electrostimulation results demonstrated that caudal lumbar splanchnic nerves provide primary control over the porcine bladder neck in comparison to other constituent fibers within the aortic plexus. Ex vivo human data revealed that the prehypogastric ganglion contains a significant number of neurons projecting to the superior hypogastric plexus, and that these neurons are arranged in a topographic manner within the ganglion. Altogether, these findings suggest that a pivotal sympathetic pathway mediating bladder neck contraction courses through the caudal lumbar splanchnic nerves, prehypogastric and inferior mesenteric ganglia and superior hypogastric plexus.

Paracervical ganglion in the female pig during prenatal development: Morphology and immunohistochemical characteristics

The present study investigated the development of the paracervical ganglion in 5-, 7- and 10-week-old porcine foetuses using double labelling immunofluorescence method. In 5-week-old foetuses single PGP-positive perikarya were visible only along the mesonephric ducts. They contained DβH or VAChT, and nerve fibres usually were PGP/VAChT-positive. The perikarya were mainly oval. In 7-week-old foetuses, a compact group of PGP-positive neurons (3144±213) was visible on both sides and externally to the uterovaginal canal mesenchyme of paramesonephric ducts. Nerve cell bodies contained only DβH (36.40±1.63%) or VAChT (17.31±1.13%). In the 10-week-old foetuses, the compact group of PGP-positive neurons divided into several large and many small clusters of nerve cells and also became more expanded along the whole uterovaginal canal mesenchyme reaching the initial part of the uterine canal of the paramesonephric duct. The number of neurons located in these neuronal structures increased to 4121±259. Immunohistochemistry revealed that PGP-positive nerve cell bodies contained DβH (40.26±0,73%) and VAChT (30.73±1.34%) and were also immunoreactive for NPY (33.24±1,27%), SOM (23.6±0,44%) or VIP (22.9±1,13%). Other substances studied (GAL, NOS, CGRP, SP) were not determined at this stage of the development. In this study, for the first time, the morphology of PCG formation in the porcine foetus has been described in three stages of development. Dynamic changes in the number of neurons and their sizes were also noted, as well as the changes in immunochistochemical coding of maturing neurons.

Clarification of the Innervation of the Bladder, External Urethral Sphincter and Clitoris: A Neuronal Tracing Study in Female Mongrel Hound Dogs

Many studies examining the innervation of genitourinary structures focus on either afferent or efferent inputs, or on only one structure of the system. We aimed to clarify innervation of the bladder, external urethral sphincter (EUS) and clitoris. Retrograde dyes were injected into each end organ in female dogs. Spinal cord, mid-bladder, and spinal, caudal mesenteric, sympathetic trunk and pelvic plexus ganglia were examined for retrograde dye-labeled neurons. Neurons retrogradely labeled from the bladder were found primarily in L7-S2 spinal ganglia, spinal cord lateral zona intermedia at S1-S3 levels, caudal mesenteric ganglia, T11-L2 and L6-S2 sympathetic trunk ganglia, and pelvic plexus ganglia. The mid-bladder wall contained many intramural ganglia neurons labeled anterogradely from the pelvic nerve, and intramural ganglia retrogradely labeled from dye labeling sites surrounding ureteral orifices. Neurons retrogradely labeled from the clitoris were found only in L7 and S1 spinal ganglia, L7-S3 spinal cord lateral zona intermedia, and S1 sympathetic trunk ganglia, and caudal mesenteric ganglia. Neurons retrogradely labeled from the EUS were found in primarily at S1 and S2 spinal ganglia, spinal cord lamina IX at S1-S3, caudal mesenteric ganglia, and S1-S2 sympathetic trunk ganglia. Thus, direct inputs from the spinal cord to each end organ were identified, as well as multisynaptic circuits involving several ganglia, including intramural ganglia in the bladder wall. Knowledge of this complex circuitry of afferent and efferent inputs to genitourinary structures is necessary to understand and treat genitourinary dysfunction. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.

Striated Perineal Muscles: Location of Somatic and Autonomic Neurons Projecting to the Male Pig Ischiocavernous Muscle. Neurochemical Features of the Sympathetic Subset

The location, number and size of the central and peripheral neurons innervating the ischiocavernous muscle (ICM) were studied in male pigs by means of Fast Blue (FB) retrograde neuronal tracing. Moreover the immunohistochemical properties of the sympathetic ganglia were investigated combining the double immunolabeling method. After injection of FB into the left ICM, a mean number of 245.3 ± 134.9 labeled neurons were found in the ipsilateral ventral horn of the S1-S3 segments of the spinal cord (SC), 129.7 ± 45.5 in the L6-S3 ipsilateral and S2-S3 contralateral spinal ganglia (SGs), 2279.3 ± 622.1 in the ipsilateral L2-S2 and contralateral L5-S2 sympathetic trunk ganglia (STGs), 541.7 ± 158 in the bilateral caudal mesenteric ganglia (CMGs), and 78.3 ± 35.8 in the microganglia of the pelvic plexus (PGs). The mean area of the ICM projecting neurons was 1217 ± 69.7 μm² in the SC, 2737.5 ± 176.5 μm² in the SGs, 982.8 ± 36.8 μm² in the STGs, 865.9 ± 39.14 μm² in the CMGs and 426.2 ± 24.72 μm² in the PGs. The FB positive neurons of autonomic ganglia contained Dopamine β hydroxylase, vesicular acetylcholine transporter, neuronal nitric oxyde sinthase, calcitonine gene related peptide, leu-enkephaline, neuropeptide Y, substance P, vasoactive intestinal polypeptide, and somatostatine often colocalized with tyrosine hydroxylase. The particular localization of the motor somatic nucleus, the abundant autonomic innervation and the qualitatively different content of ICM projecting sympathetic neurons suggest a complex regulation of this striated muscle involved in involuntary functions, such as the erection, ejaculation, micturition and defecation. Anat Rec, 301:837-848, 2018. © 2017 Wiley Periodicals, Inc.

Sensory and autonomic neurons project both to the smooth retractor penis and to the striated bulbospongiosus muscles. Neurochemical features of the sympathetic subset

Aim of the present study was to verify, by means of double retrograde neuronal tracers technique, the hypothesis that a subpopulation of sensory and autonomic neurons send collateral axons to both smooth and striated genital muscles. We also wanted to define the neurochemical content of the eventually retrogradelly double labeled (RDL) neurons in the sympathetic trunk ganglia (STG). We used six intact pigs and we injected the tracer Diamidino Yellow (DY) in the smooth left retractor penis muscle (RPM) and the tracer Fast Blue (FB) in the striated left bulbospongiosus muscle (BSM). Rare (2 ± 0.6) RDL neurons were found in the ipsilateral S2 spinal ganglion (SG), 220 ± 42 in the ipsilateral STGs, from L3 to S3, 19 ± 15 in the contralateral S1-S2 ones and 22 ± 5 in the bilateral caudal mesenteric ganglia (CMG). The RDL neurons of the STG were IR for TH (85 ± 13%), DβH (69 ± 17%), NPY (69 ± 23%), nNOS (60 ± 11%), LENK (54 ± 19%), VIP (53±26%), SOM (40 ± 8%), CGRP (34 ± 12%), SP (31 ± 16%), and VAChT (28 ± 3%). Our research highlights the presence of sensory and sympathetic neurons with qualitatively different neurochemical content sending axons both to the smooth RPM and to the striated BSM of the pig. These RDL neurons are likely to project to the smooth vasal musculature to create the ideal physiological conditions in which these muscles can optimize the erectile function.

Experimental study on the location of neurons associated with the first sacral sympathetic trunk ganglion of the pig

The neurons associated with the left first sacral sympathetic trunk ganglion (STG S1), an autonomic ganglion particularly concerned in the innervation of the smooth and striated musculature associated with pelvic organs, were identified in the pig, using the non-trans-synaptic fluorescent retrograde neuronal tracer Fast Blue. The labelled neurons were located mostly ipsilaterally, in the intermediolateral nucleus of the spinal cord segments T10-L5, in the sympathetic trunk ganglia L3-Co1, in the caudal mesenteric ganglia, in the pelvic ganglia, and in the spinal ganglia T13-S4. Our results could indicate the existence of visceral neuronal circuits concerning the ganglia of the sympathetic trunk and the caudal mesenteric, pelvic and spinal ganglia with or without the intervention of the central nervous system, whose identification and preservation during surgical treatments could be helpful in reducing the risk of subsequent urinary and sexual disfunctions.