Multiple vasodilator pathways from the pelvic plexus to the penis of the rat.

The main penile or cavernous nerve is usually regarded as the most important vasodilator projection in the rat. Although other descending pathways have been described, there is little detailed information on their importance. In this present report, we provide topographic and quantitative information on lateral and ventral penile branches and examine the vasodilator fibers which join the pudendal neurovascular bundle.

Preganglionic fibers in the rat hypogastric nerve project bilaterally to pelvic ganglia.

Stimulation of the hypogastric nerve (HGN) often evokes bilateral responses in some pelvic organs. Retrograde labeling studies indicate that axons of postganglionic neurons often cross to the opposite side. However, there is little information available as to whether preganglionic fibers in the HGN have a contralateral projection to pelvic ganglia.

Cytochrome oxidase staining in the major pelvic ganglion of the male rat.

Cytochrome oxidase staining was used as a marker of metabolic activity in neural elements in the rat major pelvic ganglion. Many neurons in the ventral pole of the ganglion have little cytochrome oxidase activity, while neurons in other locations show gradations in staining intensity. Punctate staining around principal neurons may represent preganglionic terminals, since it was greatly reduced after denervation of the ganglion.

The sensory branch of the pudendal nerve is the major route for adrenergic innervation of the penis in the rat.

Background: Multiple pathways have been proposed for the course of adrenergic fibers to the penis and, although it is generally recognized that the pudendal nerve (PudN) is the most important, there is little quantitative information available.

Methods: We used image analysis of catecholamine histofluorescence to quantify the effect of various nerve lesions on the adrenergic innervation of the rat penis. In addition to the denervation studies and as a direct test of whether penile adrenergic fibers traversed the pelvic plexus, penile neurons in the sympathetic chain were first labeled with a retrograde dye placed in the penis.

Selective upregulation of arterial endothelial nitric oxide synthase in pulmonary hypertension.

We have previously demonstrated that arterial, but not venous, vasodilatory responses to endothelium-derived nitric oxide (EDNO)-dependent agonists are enhanced in lungs isolated from rats with chronic hypoxia (CH)-induced pulmonary arterial hypertension. These data suggest that CH is associated with increased endothelial nitric oxide synthase (eNOS) activity within the pulmonary arterial vasculature. In addition, the correlation of increased pulmonary arterial pressure with selectively enhanced arterial responsiveness to EDNO-mediated agonists suggests that arterial hypertension, rather than hypoxia per se, is a contributing factor in this response.

Denervation-induced changes in perineuronal plexuses in the major pelvic ganglion of the rat: immunohistochemistry for vasoactive intestinal polypeptide and tyrosine hydroxylase and histochemistry for NADPH-diaphorase.

To characterize further the injury response of autonomic ganglia, we have examined the effect of chronic denervation on perineuronal plexuses that are immunoreactive for vasoactive intestinal polypeptide (VIP) and tyrosine hydroxylase (TH) or that stain for nicotinamide adenine dinucleotide phosphate (NADPH) in the rat major pelvic ganglion, and their relationship to an identified sub-population of neurons in the ganglion (the penile neurons). Penile neurons contain VIP and NADPH diaphorase (NADPH-D) but lack TH. VIP-immunoreactive (VIP-IR) and TH-IR perineuronal plexuses (baskets) are rare in the rat major pelvic ganglion and those present are not associated with penile neurons.

The pelvic plexus: innervation of pelvic and extrapelvic visceral tissues.

The pelvic plexus is an association of neurons that govern visceral tissues involved in eliminative and reproductive functions. It is the singular site in the autonomic nervous system where sympathetic and parasympathetic neurons occur in the same ganglia. Within the plexus, ganglia are not randomly positioned; sympathetic neurons tend to occur more ventrally while parasympathetic neurons are located more dorsally, both in accordance with the location of their target tissues and the entry point of their corresponding preganglionic nerve tracts.

Neural and endothelial nitric oxide synthase activity in rat penile erectile tissue.

NADPH-diaphorase (NADPH-D) activity and immunoreactivity for neural and endothelial nitric oxide synthase (nNOS and eNOS, respectively) were used to investigate nitric oxide (NO) regulation of penile vasculature. Both the histochemical and immunohistochemical techniques for NOS showed that all smooth muscles regions of the penis (dorsal penile artery and vein, deep penile vessels, and cavernosal muscles) were richly innervated. The endothelium of penile arteries, deep dorsal penile vein, and select veins in the crura and shaft were also stained for NADPH-D and eNOS.

The effect of chronic decentralization on the enkephalin immunoreactive plexus around penile ganglionic neurons.

Target organ responses to sympathetic nerve stimulation are altered following partial decentralization of the pelvic plexus in the rat. One possible explanation for the new responses is that nerve injury has led to a reorganization of synaptic connections within pelvic ganglia. Since one measure of synaptic influence is the occurrence of a pericellular plexus of varicose fibers around autonomic ganglion cells, the present study has used immunocytochemistry for enkephalin (ENK), a peptide present in nerve fibers in the pelvic plexus, to follow changes in the innervation of penile ganglionic neurons after interruption of preganglionic pathways.

Expression of nitric oxide synthase by syncytiotrophoblast in human placental villi.

The endogenous biosynthesis of nitric oxide (NO) is increased during gestation. To begin our investigation of a possible tissue source (or sources), we examined the placenta. We postulated that analogous to the endothelium of blood vessels, the syncytiotrophoblast (STr) cell layer that lines the intervillous blood space of the human placenta would express NO synthase.

NADPH diaphorase innervation of the rat anococcygeus and retractor penis muscles.

NADPH diaphorase histochemistry was used to determine whether the rat anoocccygeus (AC) and retractor penis (RP) muscles are innervated by nerves capable of synthesizing nitric oxide. In both tissues, muscle fascicles were enclosed by a varicose plexus of NADPH diaphorase positive (ND+) fibers. Perikarya of neurons on the surface of the AC muscle were also intensely stained for NADPH diaphorase.

The vasculature of the rat penis: a scanning electron microscopic and histologic study.

As a basis for understanding the mechanism of erection in an animal model frequently used in research in reproductive biology, the angioarchitecture of the penis of the rat has been described using scanning electron microscopy. Study of the penile vasculature of the rat indicates that the corpora cavernosa penis and the corpus spongiosum are independent erectile tissues, each with its own arterial and venous vessels. The large vascular spaces and abundant smooth muscle of the penile crura are compatible with its role in regulating blood flow to more distal penile tissues.

Distribution and origin of neuropeptide Y-immunoreactive fibers in the penis of the rat.

The present study investigated the distribution of neuropeptide Y-immunoreactive fibers to the penis of the rat. In the corpora cavernosa penis, a dense plexus of fibers was associated with arteries, intrinsic cavernosal muscle, and veins, including the deep dorsal vein. In the corpus spongiosum, immunoreactive fibers were present around vascular smooth muscle and at the periphery of the acini of the paraurethral glands.

The ischiourethralis muscle of the rat: anatomy, innervation, and function.

The ischiourethralis (IU), a striated perineal muscle presumed to be involved in sexual reflexes, was studied in the rat. The paired muscle arises from the penile crus and the penile bulb and unites in a raphe over the deep dorsal vein of the penis. Retrograde tracing studies show that the muscle is innervated by neurons in the dorsolateral nucleus of the lumbar spinal cord, a pudendal nerve motor nucleus which also innervates the ischiocavernosus muscle.

Cortical microstimulation thresholds adjacent to sensorimotor cortex injury.

The initial severe contralateral impairment of motor function after unilateral damage to a portion of sensorimotor (SM) cortex lessens within a few weeks after injury. In this study, two hypotheses proposed to explain recovery of behavioral function after cortical injury were tested: (1) Intact cortex adjacent to the injury reorganizes to take over the function of the destroyed area. (2) Intact SM cortex adjacent or connected to the injured area undergoes a transient shock (diaschisis), and as this dissipates, some behavioral recovery occurs.

Innervation of the anococcygeus muscle of the rat.

The innervation of the anococcygeus muscle of the rat was investigated with regard to the histochemical features of nerve fibers within the muscle and to the location of the postganglionic autonomic neurons which are the source of these fibers. Acetylcholinesterase-positive fibers and catecholaminergic fibers are abundant in the anococcygeus as well as the related retractor penis muscle. Neuronal somata, either between muscle bundles of the anococcygeus or in the connective tissue sheath, are also acetylcholinesterase-positive.

Penile erection in the rat: stimulation of the hypogastric nerve elicits increases in penile pressure after chronic interruption of the sacral parasympathetic outflow.

Penile erection, a vascular event mediated by the autonomic nervous system, is often adversely affected by injury to the spinal cord. To further characterize the laboratory rat as an animal model of penile erection and to investigate erectile responses following neural injury, the present study has examined pressor penile responses in intact rats and in animals deprived of sacral parasympathetic outflow. Increases in penile pressure result from graded stimulation of postganglionic parasympathetic fibers.

Parasympathetic nerves in penile erectile tissue of the rat contain choline acetyltransferase.

Choline acetyltransferase (ChAT), a biochemical marker of cholinergic neurons, was measured in the erectile tissue of intact rats and in rats in which postganglionic fibers from the pelvic plexus were interrupted. ChAT activity in the denervated erectile tissue fell by 56% compared to control tissues. Acetylcholinesterase positive (AChE+) nerves also fell by about 48%.

Autonomic innervation of reproductive organs: analysis of the neurons whose axons project in the main penile nerve in the pelvic plexus of the rat.

An understanding of the composition of the various nerves of the pelvic plexus is essential in the design of studies to explore the autonomic control of pelvic visceral tissues. As a correlate of this interest, the present study was designed to determine the composition of the main penile nerve in the pelvic plexus of the laboratory rat, an animal commonly used for studies of reproductive physiology. Retrograde tracing studies indicate that the main penile nerve contains neurons which project to the penile crura, the corpus spongiosum, and the bulbourethral glands.

Autoradiographic evidence of muscarinic cholinergic receptors in the corpora cavernosa penis of the rat.

Recent studies have questioned the role of acetylcholine in the physiology of penile erectile tissue. The responsiveness of penile erectile tissue to acetylcholine would depend, in part, on the presence of cholinergic receptors on the smooth muscle. The specific binding of [3H]quinuclidinyl benzilate (QNB) to cholinergic receptors in sections of penile crura of the rat was analyzed by in vitro neurotransmitter autoradiography.

Responses of smooth muscle strips from penile erectile tissue to drugs and transmural nerve stimulation.

1. The mechanical response to drugs and to electrical stimulation of nerves was investigated in isolated strips of intrinsic smooth muscle from the corpora cavernosa penis of the rat. 2.

Adrenergic innervation of the gills, pulmonary arterial plexus, and dorsal aorta in the neotenic salamander, Ambystoma tigrinum.

The presence of adrenergic innervation was investigated in four different vascular segments of the neotenic tiger salamander, Ambystoma tigrinum, by histofluorescent staining for catecholamines. The segments were the respiratory section of the gill, the branchial shunt vessels, a vascular plexus in the pulmonary artery, and the dorsal aorta. No adrenergic fibers were detected in the respiratory section of the gill or the pulmonary arterial plexus.

Composition of the pelvic nerve.

Surgical interruption of the pelvic nerve elevated immunoreactive vasoactive intestinal polypeptide in the major pelvic ganglion of the rat. Two changes were noted: (i) varicose and smooth fibers appeared in the neuropil and (ii) a small number of ganglion cells became highly reactive for the polypeptide. A more proximal transection of preganglionic parasympathetic fibers, at their origin from spinal nerves, had no effect on vasoactive intestinal polypeptide immunoreactivity.

The hypogastric nerve pathway to penile erectile tissue: histochemical evidence supporting a vasodilator role.

Retrograde dye staining, combined with histochemical and immunohistochemical techniques, were used to characterize penile neurons in the major pelvic ganglion of the rat. Of the penile neurons 92% were immunoreactive for vasoactive intestinal polypeptide, while 95% of penile neurons stained intensely for acetylcholinesterase. None of the neurons were immunoreactive for tyrosine hydroxylase.

The hypogastric nerve innervates a population of penile neurons in the pelvic plexus.

Retrograde dye staining, enkephalin immunocytochemistry and nerve lesion paradigms were used to determine if penile neurons in the pelvic plexus are innervated by fibers in the hypogastric nerve. In the intact major pelvic ganglion of the rat, some 80% of penile neurons are enclosed by an enkephalin-positive fiber plexus. Following surgical interruption of the pelvic nerve, 20% of penile neurons were still surrounded by an enkephalin plexus.