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. Seventeen Sprague-Dawley rats were used. The techniques included injection of dye in the penis to label neurons in the pelvic plexus in combination with transection of the main penile nerve (MPN). NADPH diaphorase (NADPH-d) histochemistry was used to assess the effects of transection of vasodilator pathways on innervation of the penis and for in situ staining of the pelvic plexus. Distinct clusters of penile neurons are aggregated at the origin of several nerve tracts leaving the posterior margin of the major pelvic ganglion (MPG). Multiple NADPH-d+ fiber bundles coursed over the anterior surface of the prostate to reach the penis. Branches from these tracts joined the pudendal neurovascular bundle proximal to the hilum of the penis and provided innervation to the artery throughout its course in the pudendal canal. Consistent with the presence of multiple penile pathways, transection of the MPN reduced, but did not eliminate retrograde labeling of penile neurons in the MPG and only modestly decreased NADPH-d+ fibers in the penis. This study confirms that there are multiple pathways by which vasodilator fibers reach the penis. If a similar allocation of vasodilator output is present in man, preservation of finer branches of the pelvic plexus would be important in surgical procedures on the prostate.

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. A retrograde tracer was injected into the left major pelvic ganglion (MPG) in rats receiving various lesions of preganglionic nerves (HGN and pelvic nerve, PN). The lumbar spinal cord was then examined for location and number of dye-filled neurons. In a second approach, the incidence 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 spinal cord nuclei (Lumbar1-2) after dye injection of the MPG in animals with an intact contralateral HGN. Cutting both HGNs virtually eliminated dye labeling in the lumbar cord, as did severing commissural branches (CB) between pelvic ganglia (leaving the contralateral HGN intact). Some SN-IR baskets were found in the left APG when only the contralateral HGN was intact, but baskets were rare when all four preganglionic nerves were cut. It could not be determined whether the HGN projects to the contralateral MPG, since SN-IR baskets were numerous in the MPG even when all four nerves were cut. This study has shown that some preganglionic fibers in the HGN synapse on neurons in contralateral pelvic ganglia. Both the APG and MPG receive contralateral innervation, but it is likely that neurons in the APG are the primary target of this input. Thus, in addition to crossing postganglionic fibers, a portion of the bilateral control of pelvic tissues is accomplished by preganglionic fibers which target autonomic neurons in contralateral 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. Image analysis was used to compare neuronal size to staining intensity. There was a negative correlation between cell size and staining intensity; the largest neurons were only lightly stained for cytochrome oxidase, while the medium and the small neurons showed a full range of metabolic activity. To study metabolic activity of an identified neuronal population, the seminal vesicles were injected with a retrograde tracer. The largest seminal vesicles neurons (1500 to 3200 microns2) had low enzyme activity, whereas the majority of neurons to this organ were smaller with gradations in staining. These results are indicative of the metabolic activity of the autonomic innervation to various pelvic tissues. Cytochrome oxidase histochemistry should prove valuable in assessing the demands placed on autonomic ganglia in differing functional and dysfunctional states.

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. The cavernous nerve of these animals was later exposed to another dye with different spectral characteristics.

RESULTS

Interruption of the sensory branch of the PudN reduced adrenergic innervation of cavernosal smooth muscle by 86% (+/- 2.5%). Vascular fibers of the deep penile and helicine arteries were also severely reduced but not entirely eliminated. Interruption of the motor branch of the PudN had a lesser and more variable effect on penile adrenergic innervation: a 21.2% (+/- 6.8%) decrease in cavernosal muscle innervation but no obvious affect on vasomotor fibers. Combining the nerve lesions with phenol degeneration of perivascular fibers of the pudendal vessels further reduced but did not entirely eliminate adrenergic fibers in the cavernosal muscle and penile vessels.

CONCLUSIONS

The dramatic reduction of adrenergic innervation of the penis after section of the PudN, especially the sensory branch, and the absence of double-labeled neurons in the sympathetic chain suggest that the PudN nerve is the major, if not the exclusive, pathway by which adrenergic fibers reach penile erectile tissue of the rat.

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. Therefore, we hypothesized that 1) CH selectively upregulates eNOS within the pulmonary arterial vasculature and 2) monocrotaline (MC)-induced pulmonary arterial hypertension selectively enhances pulmonary arterial dilation to EDNO-dependent dilators and upregulates arterial eNOS. We examined the responses to the EDNO-dependent dilators arginine vasopressin and ionomycin in U-46619-constricted isolated perfused lungs from control and MC-treated rats. Microvascular pressure was assessed by the double-occlusion technique, allowing calculation of segmental resistances. Lungs from MC-treated rats exhibited augmented arterial dilation to arginine vasopressin compared with control lungs. However, the responses to ionomycin were not different between the two groups. Quantitative immunocytochemistry was used to compare pulmonary eNOS immunoreactivity in vessels from control, CH, and MC-treated rats. eNOS staining was more intense in the arteries of CH and MC-treated rats compared with those of control animals, whereas CH and MC treatment had no effect on eNOS staining in veins. We conclude that pulmonary arterial hypertension, or altered vascular mechanical forces associated with hypertension, may be responsible for the augmented EDNO-dependent arterial dilation and upregulation of arterial eNOS in lungs from CH and MC-treated rats.

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. A small increase in VIP-IR baskets occurs 2 weeks after proximal interruption of the pelvic nerve, but TH-IR baskets increase five-fold. The emergent VIP-IR and TH-IR baskets enclose TH-negative neurons, none of which are penile ganglion cells. These changes remain up to 4 weeks after denervation. Interrupting the pelvic nerve nearer the margin of the major pelvic ganglion results in a rapid, more dramatic increase in VIP-IR, in cell bodies and beaded fibers, than that seen with the more proximal lesion. About 27% of neurons in the ventral pole of the ganglion are enveloped by NADPH-D perineuronal baskets. The incidence of NADPH-D baskets falls to less than 1% after acute interruption of the pelvic and hypogastric nerves, but their frequency returns to control levels in chronically denervated ganglia. The rapid, vigorous changes in peptide (VIP) fibers after the pelvic nerve is cut close to the major pelvic ganglion may be attributable to the interruption of axons of postganglionic neurons and to preganglionic nerve fibers, whereas the slowly developing changes in VIP-IR and TH-IR fibers after more proximal lesions may represent the more modest effects of true decentralization. The source and significance of the VIP-IR, TH-IR, and NADPH-D baskets that appear in chronically denervated ganglia remain unclear.

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. For example, the vas deferens and seminal vesicle are ventral in position and thus are innervated by more ventrally located pelvic neurons. Neurochemical studies of pelvic ganglia indicate that there are some characteristic associations of putative neurotransmitters which are based on target organ distribution and in part, dictated by the variety of target tissues within each organ. Penile neurons comprise a uniform population in that they are cholinergic and also may release vasoactive intestinal polypeptide (VIP) and nitric oxide. In contrast, target tissues of the internal genitalia are more diverse, requiring adrenergic and nonadrenergic innervation and a complementary neuropeptide. Preganglionic innervation may also be coded and although sympathetic and parasympathetic fibers are cholinergic, they may differ in respect to neuropeptides and nitric oxide. Sensory neuron collaterals may also influence principal neurons as do intrinsic neurons such as small intensely fluorescent cells. Transmission through pelvic ganglia may be simple as is apparent in penile innervation, or shows a greater integrative capacity, as exemplified by the innervation of the urinary bladder. The extent of interaction of sympathetic and parasympathetic pathways at the level of the pelvic plexus remains largely unknown.

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. However, the endothelium of cavernous sinuses was unstained by both techniques. Fewer fibers were seen in the glans penis, those present being associated with small blood vessels and large nerve bundles near the trabecular walls. All penile neurons in the pelvic plexus, located by retrograde transport of a dye placed in the corpora cavernosa penis, were stained by the NADPH-D method. Essentially similar results were obtained with an antibody to nNOS. These data suggest that penile parasympathetic neurons comprise a uniform population, as all seem capable of forming nitric oxide. However, in contrast to the endothelium of penile vessels, the endothelium lining the cavernosal spaces may not be capable of nitric oxide synthesis.

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. Penile ganglion cells were located by the injection of the tracer Fluorogold into the penile crura. Four days after lesion of the pelvic nerve, innervation of penile neurons falls from 76% to 20%. This number increases however, to 31% in chronically (6 weeks) lesioned animals. In the totally decentralized ganglia, ENK immunoreactive (IR) fibers enclose fewer than 12% of the penile neurons 4 days after nerve lesion. However, this value rises to 35% in the chronically decentralized pelvic ganglion. Therefore, recovery of an enkephalin plexus occurs irrespective of whether the pelvic nerve, or both the hypogastric and pelvic nerve have been cut. Although these findings suggest sprouting within partially decentralized ganglia, the similar incidence of an ENK plexus in ganglia subjected to chronic partial or total decentralization indicates that preganglionic fibers are not responsible for the emergent fibers.

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. Our results show that human placental villi express a calcium- and calmodulin-sensitive form of NO synthase, located mainly in the microsomal cell fraction. By in situ hybridization using a riboprobe generated from human endothelial NO synthase cDNA, we observe NO synthase mRNA expression in STr. The STr also shows NADPH-diaphorase staining, indicating the presence of NO synthase, and most likely other flavin-containing enzymes involved in sex steroid metabolism. NO synthase activity was also detected in the villi of a complete mole placenta (which lacks fetal vessels), further supporting a trophoblastic origin. Our findings suggest a previously unrecognized role for STr-derived NO in placental function.

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. Many AC-RP ganglion cells in the pelvic plexus, located by the retrograde tracer Fluorogold, also stained for the enzyme. However, a significant population of AC-RP neurons in this location remained unstained. These results provide further evidence that nitric oxide may be an important neurotransmitter in these tissues.

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. Helicine arteries of the crura, but not the parent deep penile artery or arteries elsewhere, have muscular cushions in their walls. The venous drainage of the penile crura is via subtunical veins which are thought to be compressed during erection to elevate pressure within the penis. Large, paired cavernous veins drain the shaft of the penis. A unique method for inhibiting blood flow from the penis is indicated by the division of the cavernous veins into smaller channels prior to joining the subtunical venous plexus. Erectile tissue in the bifid origins of the corpus spongiosum has abundant cavernous muscle, while in the remainder of the corpus spongiosum little smooth muscle lines the cavernous spaces. The cavernous spaces on either side of the urethra coalesce to form vessels, each of which communicates with cavernous spaces in the glans. In addition, a bypass of the glans is effected by communication of these vessels directly with the deep dorsal vein. The apparent absence of muscular pads in vessels of the spongiosum, the relative paucity of cavernous smooth muscle, and the ample venous drainage provided by the deep dorsal vein may account for the lack of a venous occlusive mechanism similar to that of the corpora cavernosa penis.

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. Immunohistochemistry of penile neurons identified by retrograde tracer injection into the penis indicates that about 5% of the penile neurons in the pelvic plexus contained the neuropeptide while larger percentages of penile neurons in the sympathetic chains were immunoreactive for neuropeptide Y. Chemical and surgical sympathectomy greatly reduced the neuropeptide Y- and catecholamine-containing fibers in the erectile tissue but had no clear effect on the neuropeptide Y fibers around the paraurethral glands; a tissue that is not innervated by adrenergic fibers. It is concluded that (1) the widespread distribution of neuropeptide Y indicates that it may function in the control of penile blood flow, (2) with the possible exception of the paraurethral glands, the sympathetic chain is the most likely source of neuropeptide Y fibers in both erectile bodies of the penis, and (3) this peptide may play a role in the secretory functions 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. Excision of the IU muscle did not interfere with the ability of males to display normal copulatory behavior, nor did it affect significantly the number and intensity of reflexive erections. It nevertheless remains possible that the IU may contribute to intense glans erection by compressing the deep dorsal vein.

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. Using microstimulation of the cortex of the adult rat, movements evoked from areas near cortical injuries were studied at various times after undercut laceration, contusion, or suction ablation of an area of SM cortex. Stimulation areas were compared to those obtained from uninjured control animals and to the contralateral uninjured hemisphere. No evidence was obtained for any reorganization of stimulated motor responses in the injured hemisphere even in animals followed for as long as 475 days postinjury, suggesting other mechanisms underlying functional recovery. In intact cortex at some distance from contusion and laceration injuries, there was a marked elevation of thresholds to evoke movements that returned to normal by 9-15 days postinjury. Some intact hindlimb responses were observed after contusion injury that were absent in animals after 15 days postinjury, indicating a slow-growing lesion after this type of trauma. Surprisingly, no elevation in thresholds was noted for ablation injuries up to the edge of the cavity at any time postinjury, indicating that threshold changes near the boundary may be uncorrelated with functional recovery.

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. Nerve fibers and a minority of the ganglion cells in the anococcygeus and retractor penis muscles are immunoreactive for vasoactive intestinal polypeptide. Injection of the retrogradely transported dye Fluorogold into the anococcygeus muscle filled neurons in the abdomino-pelvic sympathetic chain, pelvic plexus and a small number of neurons in the inferior mesenteric ganglion. In the pelvic plexus, some neurons were located in the major pelvic ganglion but most were found along the main penile nerve and its branches to the anococcygeus muscle. Immunocytochemistry of these identified neurons indicates that about one half of them are positive for vasoactive intestinal polypeptide. These results raise the possibility that both acetylcholine and vasoactive intestinal polypeptide are important neurotransmitters in autonomic nerves to the anococcygeus muscle.

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. The vasodilator response is insensitive to blockade with atropine, a cholinergic antagonist. Penile tumescence also results from stimulation of the pelvic nerve, but not the hypogastric nerve. However, beginning 3 days after unilateral interruption of the pelvic nerve, stimulation of the ipsilateral hypogastric nerve results in an increase in penile pressure. This novel response, which is blocked by a ganglionic antagonist, is maximally developed at 1 week post-lesion, is stable for at least 3 months and remains confined to the side of the lesion. These results suggest that the rat, although relatively small, can be used to obtain quantitative data on penile erection. Moreover, the model may lend itself to an analysis of the mechanisms of altered control of visceral tissues following injury to the nervous system.

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%. Penile neurons distal to the lesion probably account for the residual ChAT activity and remaining AChE+ nerve fibers in erectile tissue. These results indicate that acetylcholine is an important neurotransmitter in the regulation of penile erection.

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. The main penile nerve is the major source of neurons which innervate the corpus spongiosum and bulbourethral gland and contains about one-third of all parasympathetic neurons which project to the penile crura. Dye placed on the proximal cut end of the main penile nerve indicates that neurons in the parasympathetic region of the spinal cord (L6-S1) and to a lesser extent a sympathetic region of the cord, L1-L2, provide preganglionic innervation to ganglion cells in the main pelvic nerve. Processes of neurons in dorsal root ganglia L6-S1 and of neurons in the abdominopelvic sympathetic chain course in the main penile nerve to unknown destinations. In many respects this presumed postganglionic fiber tract is essentially a region of the pelvic plexus which subserves extrapelvic visceral tissues.

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. Silver grain density measurements indicated that muscarinic cholinergic receptor binding sites are located almost entirely over the corpora cavernosa penis. Virtually no specific [3H]QNB binding was present in the tunica albuginea or adjacent skeletal muscle tissue. Within the erectile tissue, specific binding occurred both over the columns of intrinsic smooth muscle which form the walls of the cavernous spaces and around the more distal branches of the penile arteries. The high concentration of muscarinic cholinergic receptors in the corpora cavernosa penis is consistent with the suggestion that acetylcholine has an important, albeit undefined role in the function of penile erectile tissue.

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. Noradrenaline caused muscle strips to contract in a dose-dependent manner. Contractions could be blocked by pretreatment with the alpha-adrenoreceptor antagonist, phentolamine. 3. Acetylcholine and carbachol had no effect on the baseline tension of muscle strips. Both drugs were relatively ineffective in relaxing noradrenaline-contracted strips. 4. Field stimulation of isolated muscle strips elicited contractions which were blocked by tetrodotoxin and greatly attenuated with phentolamine or reserpine pretreatment. Acetylcholine inhibited the excitatory response to field stimulation. This inhibitory effect of acetylcholine could be blocked with atropine. 5. Field stimulation of noradrenaline-contracted muscle strips caused relaxation. This inhibitory effect, due to nerves which arise from the pelvic plexus, is unaffected by substances which act on cholinergic systems. 6. The results suggest that the erectile muscle of the rat is similar to that of man in that it receives an excitatory noradrenergic innervation and an inhibitory innervation which may have a non-cholinergic component. Although acetylcholine may have a role in penile physiology of the rat, it is unlikely that it has a postsynaptic action.

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. In contrast, the branchial shunt vessels contained both adrenergic varicosities and catecholamine-containing cell bodies. These cells resemble Type I cells of the mammalian carotid body and amphibian carotid labyrinth. Adrenergic innervation of the dorsal aorta was sparse and restricted to the adventitia. The results suggest that adrenergic nerves may directly regulate blood flow in the gill, and thus gas exchange, by controlling vascular resistance of the branchial shunts. The contractile state of the dorsal aorta may also be under adrenergic control. In addition, it is suggested that the adrenergic cells of the branchial shunts may serve a receptor function in being sensitive to arterial blood gases.

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. Ganglion cells were labeled when a dye was applied to the cut distal end of the pelvic nerve. We conclude that a population of vasoactive intestinal polypeptide-containing neurons in the major pelvic ganglion send their axons proximally in the pelvic nerve.

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. Penile neurons in the pelvic plexus receive preganglionic input from the pelvic and the hypogastric nerve, yet the shared histochemical features of the postganglionic neurons suggest that the two pathways have a similar role in penile erectile tissue.

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. After interruption of the pelvic nerve and the hypogastric nerve, the enkephalin plexus in the ganglion was virtually absent, including the plexus around penile neurons. Therefore, possible intrinsic sources of the enkephalin fibers such as enkephalin-positive principal neurons and small intensely fluorescent cells, do not account for the delicate enkephalin fiber system in the pelvic ganglion. It is concluded that the pelvic nerve is the major source of preganglionic innervation to penile neurons in the major pelvic ganglion. However, it is significant that the hypogastric nerve is preganglionic to about 20% of penile neurons. The pathway through the hypogastric nerve may represent an alternate vasodilator system to penile erectile tissue.

Substance P immunoreactivity in the major pelvic ganglion of the rat

Substance P immunoreactivity in the major pelvic ganglion (MPG) of the rat was studied to define a possible role for this neuropeptide in functions of the pelvic portion of the autonomic nervous system. Substance P immunoreactivity was found in three locations in the ganglion: 1) as a plexus of varicose fibers, 2) in small intensely fluorescent (SIF) cells, and 3) after colchicine pretreatment, in some principal neurons. The perineuronal plexus of fibers appeared as small varicosities closely related to the somae of principal neurons. Approximately 10-20% of principal neurons were enclosed by a substance P-positive plexus. SIF cells were intensely stained for substance P. The general relationships of SIF cells in this ganglion were confirmed by their staining for substance P: their occurrence singly or in large clusters, their short tapering processes often related to principal neurons, and the occasional presence of a beaded process. Colchicine treatment resulted in the appearance of rare principal neurons that stained for substance P. The pelvic nerve was surgically interrupted to determine whether the perineuronal plexus of varicose fibers had an intrinsic origin or arose from cell bodies outside the ganglion. The perineuronal plexus was virtually absent following this procedure. The results of this study indicate that principal neurons in the major pelvic ganglion may be subject to the influence of substance P derived from two sources: 1) intrinsic substance P-containing SIF cells and 2) neurons probably residing in dorsal root ganglia. The nature of principal neurons that acquire staining for substance P after colchicine is unclear.

Localization of vasoactive intestinal polypeptide in penile erectile tissue and in the major pelvic ganglion of the rat

Vasoactive intestinal polypeptide was localized by immunocytochemical techniques in the major pelvic ganglion and penile erectile tissue of the rat. Vasoactive intestinal polypeptide fibers were concentrated in penile crura with the density of innervation decreasing distally. The helicine arteries were very densely innervated while fewer fibers surrounded the deep artery of the penis. Intrinsic smooth muscle of the cavernous bodies received a moderate supply of vasoactive intestinal polypeptide immunoreactive fibers. Dorsal vascular structures, including the deep dorsal vein were innervated by vasoactive intestinal polypeptide fibers. Vasoactive intestinal polypeptide immunoreactive cell bodies were found in the major pelvic ganglion, concentrated on one end of the ganglion. Retrograde studies with a dye injected into the penile crura indicated that neurons in major pelvic ganglion projected to the penis. Combined dye and immunofluorescent studies showed that all the dye-labeled neurons were immunoreactive for vasoactive intestinal polypeptide. It is concluded that all vascular beds in the penis of the rat are innervated by vasoactive intestinal polypeptide fibers and that the extent of the innervation is related to the occurrence of smooth muscle. Neurons in the major pelvic ganglion probably are the main source of vasoactive intestinal polypeptide fibers to the penis.

Evidence for direct neural control of ovarian steroidogenesis in rats

Electrical stimulation of the superior ovarian nerve of intact anaesthetized dioestrous rats for 30 min reduced ovarian progesterone levels, even when papaverine and propranolol were also given. The administration of phentolamine (an alpha receptor antagonist) before stimulation reversed this effect. The results suggest that a neural control of ovarian steroidogenesis may be either excitatory through the stimulation of beta receptors or inhibitory through the stimulation of alpha receptors.

Modified radical mastectomy with immediate breast reconstruction

Surgery for breast cancer continues to evolve. Less radical procedures and increasing concern about appearance and rehabilitation are now the trend. Such considerations prompted a detailed anatomic study and review of the location and course of the medial and lateral pectoral nerves, the development of a technique for immediate reconstruction of the breast during modified radical mastectomy that protects the innervation of the pectoral muscles and incorporates them in the construction of a submuscular pocket to receive a silicone breast prosthesis, and the administration of low doses of heparin sodium to prevent necrosis of ischemic breast flaps. Fifty immediate reconstructions of the breast after modified radical mastectomy were performed in 48 women with carcinoma of the breast. We believe this procedure greatly enhances rehabilitation and quality of life without diminishing the ability to diagnose or treat recurrent disease.

The Manx cat as an animal model for neurogenic vesical dysfunction associated with myelodysplasia: a preliminary report

The Manx cat breeds consistently for spinal dysraphism (myelodysplasia) and has spinal cord neuropathologic abnormalities similar to those of myelodysplastic humans. The results of detailed urodynamic and histochemical evaluation of 1 Manx kitten and limited anatomic study of another Manx kitten are described. Urodynamic evaluation revealed significant abnormalities of vesicourethral function: detrusor areflexia, autonomous pressure response to bladder filling, a dysfunctional proximal urethra and poor quality pelvic floor electromyographic activity. Of particular interest, catecholaminergic histochemical studies of the bladder and urethra demonstrated a complete absence of adrenergic fibers, even in the trigone area where they are reported to be abundant. This finding correlated with the urodynamic dysfunction of the proximal urethra. Cholinergic histochemical studies were normal. Examination of the spinal cord revealed moderate hydromyelia throughout the entire length of the cord. The similarities of normal vesicourethral function in man and the cat and our preliminary findings of vesicourethral dysfunction in the Manx cat suggest that this animal may be a particularly valuable model for further research.

Cardiac catecholamine stores after cardiac sympathectomy, 6-OHDA, and cardiac denervation

Sympathetic nerves are known to reach the heart via classical vagal pathways. Bilateral cervicothoracic sympathectomy (CS) might be expected therefore to leave significant amounts of releasable catecholamines in the myocardium if the vagi are left intact. Cardiac responses to tyramine (500 micrograms intracoronary) were compared in animals with CS, extrinsic cardiac denervation (CD), and chemical sympathectomy with 6-hydroxydopamine (6-OHDA). Dogs were placed on cardiopulmonary bypass and isovolumic pressures were recorded from the heart. In control animals, tyramine caused profound increases in rate (58%) and isovolumic pressures (86-170%). Ten CS animals demonstrated responses indistinguishable from control animals. Four CD and four 6-OHDA animals showed no response to tyramine. Cervical vagal stimulation after atropine in the CS animals produced tachycardia. Histofluorescent studies demonstrated the presence of significant numbers of cardiac adrenergic fibers in this group. The normal tyramine responsiveness of the CS animals was attributed to 1) significant numbers of vagal adrenergic fibers remaining in the heart after cervicothoracic sympathectomy, and 2) denervation supersensitivity, rendering the heart very responsive to the catecholamine that remains.

Responses to cortical injury: II. Widespread depression of the activity of an enzyme in cortex remote from a focal injury

As a part of a broader study of the reaction of the brain to injury, we report here an interesting loss of the activity of an enzyme in areas quite remote from the site of direct injury. At 36 h following a laceration or contusion injury to the hindpaw area of the motor cortex, a peculiar loss of staining for the enzyme alpha glycerophosphate dehydrogenase (alpha-GPDH) was noted. alpha-GPDH activity was markedly depressed in cortical layers II and III throughout the hemisphere on the side of the injury. The depression of alpha-GPDH activity extended far laterally across the rhinal fissure into the pyriform cortex. The decrease in alpha-GPDH staining was prominent 4 days after the injury: however, the staining pattern had returned to normal at 9 days. Enzyme changes in animals lesioned in the occipital cortex paralleled that seen in animals with a lesion in the motor cortex. Animals which had received an undercut lesion in the motor cortex 56 days earlier were contused in the occipital cortex. The old injury site presented the same sequelae of changes as seen in other lesioned animals. Additionally, a suction ablation injury involving only a small part of motor cortex resulted in the same widespread reduction of staining for alpha-GPDH in layers II and III. The derangement in energy metabolism suggests that cells in layers II and III of the cerebral cortex may be particularly vulnerable to perturbations induced by cortical trauma. These findings may be related to the diffuse and transient functional losses observed after head injury in man.

Responses to cortical injury: I. Methodology and local effects of contusions in the rat

In order to develop some understanding of the evolution of cortical contusions, interdisciplinary studies including behavior, morphology and histochemistry were conducted at varying intervals after standardized injuries. A method for producing graded and reproducible focal cortical contusions in the rat is described. When these impact injuries are made in the "hindpaw cortical area,' specific trauma dose dependent behavioral deficits can be readily observed in the contralateral hindlimb. While most functional recovery occurs in the first two weeks after trauma, with severe contusions, deficits persist beyond 90 days. Morphologically these injuries progress from hemorrhages in white matter directly under contused cortex during the first hours after injury to the development of a necrotic cavity by 24 hours. The cavitation appears to expand over the subsequent two weeks and by 15 days is lined with fibroblast-like elements and macrophages. Intense acid phosphatase activity is seen on the borders of the area of necrosis. This lysosomal enzyme may participate in autolysis and development of focal cavitation following cortical contusion.

Effects of p-chloroamphetamine, a serotonin-depleting drug, on the median eminence and pituitary pars intermedia

p-Chloroamphetamine (PCA), an agent known to cause depletion of levels of brain serotonin in rodents, was administered to rats in three sequential injections (10mg/kg) to study effects on the hypothalamic median eminence and pituitary gland. One week following the initial sequence of injections of PCA, light and electron micrographs revealed degenerate fibers in the outer zone of the median eminence. Lower drug doses or single 10-mg/kg doses did not lead to morphologic changes. Neuronal processes located in the pituitary intermediate lobe appeared normal although there was a significant increase in the numbers of secretory granules contained within intermediate lobe cells drug-treated rats, as compared to controls. Fluorometric analysis of levels of catecholamine and indoleamine showed a decrease in serotonin in median eminence and pons-medulla, but no change in that of the pituitary. Levels of dopamine and norepinephrine remained unchanged after PCA treatment. The data suggest that fibers affected in the median eminence contain serotonin. Processes in the intermediate lobe may be resistant to the serotonin-lowering effects of PCA observed in brain tissue. In addition, PCA may directly affect granule release from pituitary cells, or may alternatively act on hypothalamic regions which affect the release of intermediate lobe cell hormones.

Morphology and physiology of the McLeod erythrocyte. I. Scanning electron microscopy and electrolyte and water transport properties

The McLeod phenotype is a rare condition characterized by deficiencies in the Kell blood group antigens of erythrocytes. The present study has defined some of the morphological and physiological characteristics of these red cells. Scanning electron microscopy reveals that approximately 27% of McLeod cells are morphologically abnormal. These aberrant forms resemble the acanthocytes of abetalipoproteinemia. Incubation experiments indicate that the morphology of McLeod erythrocytes is not due to a plasma factor. Biochemical studies reveal that the lipid composition and microviscosity of these erythrocytes are normal. In addition, isotopic tracer experiments indicate that electrolyte transport is also within the normal range. However, osmotic water permeability is approximately 30% below normal. The absence of a lipid abnormality and other experimental data suggest that the abnormal morphology and reduced H2O permeability of the McLeod erythrocyte may be due to defective membrane protein.

Effects of chronic deafferentation on adrenergic ganglion cells and small intensely fluorescent cells

To determine the reaction of adrenergic ganglion cells and small intensely fluorescent (SIF) cells to chronic deafferentation, catecholamine fluorescence of the major pelvic ganglion (MPG) of the rat has been studied following section of the hypogastric nerve, pelvic nerve and sympathetic trunk. Only minor changes occurred following section of the hypogastric nerve; the fluorescence surrounding a few adrenergic ganglion cells became brighter. In contrast, pelvic neurectomy resulted in the appearance of numerous varicose fibres and an increase in the fluorescent intensity of fibres enclosing many ganglion cells. Varicose fibres seem to originate from adrenergic ganglion cells and SIF cells. In many instances, nests of SIF cells gave rise to radially oriented fibres. Removal of the sympathetic trunk appeared to have no effect on the MPG. It is suggested that the appearance of varicose fibres from SIF cells following deafferentation may be due to collateral sprouting of these cells or to the increased fluorescence of pre-existing processes.

Abnormalities in pelvic visceral nerves. A basis for neurogenic bladder in the diabetic Chinese hamster

In order to determine whether bladder dysfunction and hydronephrosis in diabetic Chinese hamsters are associated with nerve pathology, the pelvic visceral nerves of diabetic and normal hamsters were examined with histochemical and electron microscopic techniques. Acetylcholinesterase activity was reduced in the nerves and on smooth muscle fibers in the urinary bladder of diabetic hamsters when compared to controls. Depression of enzyme staining was most marked in those hamsters with the most severe hydronephrosis. Frequent examples of aberrant myelination were found in the pelvic plexus and urinary bladder of diabetics. Many of these myelinated fibers exhibited wide periaxonal spaces lined by unusual processes of Schwann cells. An increase in the number of microtubules in axons and circular profiles of Schwann cells, which failed to enclose axons, gave evidence of axonal degeneration or Schwann cell injury in diabetic nerves. These findings suggest that pathologic changes in pelvic visceral nerves may underlie urinary bladder dysfunction in the diabetic Chinese hamster.

Efferent arterioles in the cortex of the rat kidney

Although a number of morphological studies have investigated the vascular system of the rat kidney, minimal data are available on the detailed anatomy of the efferent arterioles located throughout the cortex of the kidney. In the present study, the renal vascular system was filled with Microfil and the various efferent arteriole patterns were examined extensively. The efferent vessels of the entire cortex appear to form three major patterns which in turn divided the cortex into three separate regions: the outer, middle and inner cortex. The efferent arterioles of the outer cortex leave the glomerulus and run perpendicular to the kidney capsule. However, as the efferent arterioles ascend, they may show three variations in the way they branch: (1a) the efferent arteriole does not branch until directly beneath the capsule, (1b) the efferent vessel begins to divide into its major branches 100-200 mum below the surface of the kidney and (1c) the efferent vessel has only a short course before giving off many side branches. In the middle cortical area, the branches of the efferent arteriole run lateral to the glomerulus. However, the efferent arterioles of the inner cortex have a few branches which run lateral to the glomerulus while most of them descend into the medulla as vasa rectae. The unique morphological features of the efferent arterioles of the outer cortex are of particular interest in light of the functional data which suggests that the reabsorption of fluid by peritubular capillaries may indeed regulate the rate of net tubular sodium reabsorption.

Scanning electron microscopy of cell surfaces following removal of extracellular material

The application of scanning electron microscopy to the study of cell surfaces is limited in intact tissues, because extracellular material may often obscure the details of nonluminal surfaces. To remove connective tissue elements we have treated human skin and both kidney, and an autonomic ganglion of the rat with hydrochloric acid and collagenase. Regional variations in the basal surface of the nephron are noted following removal of the basement membrane. The basilar interdigitations of the cells of the proximal tubule appeared as parallel ridges encircling the tubule. Ridges on the parietal epithelium of Bowman's capsule were randomly arranged and alternated with smooth surfaces. The dermal surface of the human epidermis has an alveolar or honeycomb appearance due to the elevation of the epidermal ridges and numerous pits for the dermal pegs. At higher magnifications the basal surface of cells of the stratum germinativum possessed numerous and irregular projections. Neurons with their processes are evident in the autonomic ganglion. The soma of the neurons are enclosed by flattened satellite cells. Irregular spaces between opposed satellite cells are interpreted as regions for the passage of processes related to the ganglion cells. Nodes of Ranvier were clearly seen along nerve fibers. Some pitting of the nerve fibers was also noted. The HCl-collagenase method has the advantage of the removal of collagen and basement membrane while preserving the structural integrity of the cell surface.

The major ganglion in the pelvic plexus of the male rat: a histochemical and ultrastructural study

To further evaluate the role of autonomic ganglia in the regulation of pelvic visceral activity, the neural elements in the major pelvic ganglion of the male rat have been studied with histochemixal and electron microscopic techniques. The principal findings are that the ganglion is composed of cholinergic and adrenergic ganglion cells as well as small intensely fluorescent (SIF) cells. Polarity in the ganglion is indicated by clustering of small ganglion cells which stain intensely for acetylcholinesterase (AChE) along the pelvic nerve while larger cells, with weak to moderate AChE activity, collect near small branches of the hypogatrric nerve. Some cholinergic ganglion cells are enclosed by a plexus of adrenergic terminals. SIF cells appear to be in contact with both cholinergic and adrenergic cells, although many of the fluorescent beads around adrenergic neurons may be short dendrites of ganglion cells, rather than processes of SIF cells. Two types of SIF cells may be distingiosjed on the basis of size and morphology of their granulated vesicles. Afferent synapses of the cholinergic type were common on SIF cells of the large granule and small granule type. Portions of SIF cells with large granules occur within the capsule of ganglion cells. Contacts seen here were interpreted as efferent synapses from SIF cells to the dendrites of ganglion cells.

Appearance of hormone-sensitive adenylate cyclase in the developing human heart

Highly significant (P smaller than 0.0025) increases in adenylate cyclase activity were seen at all fetal age periods (5-17 weeks) whenever sodium fluoride (5-10 mM) was added to the enzyme prepared from human myocardium. Norepinephrine (NE) at 10-4 M significantly elevated adenylate cyclase activity commencing at 6-7 weeks (P smaller than 0.01). Beginning at 8-9 fetal weeks, glucagon (6x10-6 M) effectively activated adenylate cyclase. Other hormonal agents, namely, histamine, epinephrine, and isoproterenol at 10-4 M, demonstrated an ability to activate the enzyme (P smaller than 0.025) by as early as 6-7 weeks and continued to act in this manner throughout the remainder of the developmental periods investigated. The beta blocking agents, propranolol, significantly inhibited (P smaller than 0.25) the stimulation of adenylate cyclase by NE throughout the 8-15 fetal week periods.

The intrinsic adrenergic and cholinergic innervation of the genitalia of Galago and Tupaia. The penis

The intrinsic innervation of the penises of Galago and Tupaia were studied using modern histochemical techniques. The adrenergic and cholinergic innervation of the penile vessels and intrinsic musculature in these two species were similar. However, the adrenergic nerves of Tupaia were more intensely fluorescent than in Galago. The possibility of an efferent component of the dorsal nerve of the penis is discussed.