Immunohistochemical localization of nitric oxide synthase in the autonomic innervation of the human penis

The emerging multifaceted roles of nitric oxide

Nitric oxide (NO) is a highly reactive free radical with a multitude of organ specific regulatory functions. Since 1985, NO has been the subject of numerous research efforts and as a result, has been found to play a major role in the cardiovascular, pulmonary, gastrointestinal, immune, and central nervous systems. In addition, deranged NO synthesis is the basis for a number of pathophysiologic states, such as atherosclerosis, pulmonary hypertension, pyloric stenosis, and the hypertension associated with renal failure. Traditional NO donors such as sodium nitroprusside and new pharmacologic NO adducts such as S-nitrosothiols may serve as exogenous sources of NO for the treatment of NO-deficient pathologic states. This review is an attempt to acquaint the surgical community with the fundamentals of NO biochemistry and physiology. Increased knowledge of its functions in normal homeostasis and pathologic states will enable physicians to better understand these disease processes and utilize new pharmacologic therapies.

Effects of nitric oxide on human and canine prostates

OBJECTIVES

To determine whether nitric oxide (NO) is a mediator of prostatic smooth muscle activity.

METHODS

Pharmacologic experiments using electrical field stimulation (EFS) were performed on strips of human and canine prostate.

RESULTS

EFS alone elicited frequency-dependent contractions in preparations of human and canine prostates. The greatest contractile activity was achieved at 30 Hz. In the presence of 10(-5) M guanethidine (GUA) and 2 x 10(-6) M atropine (ATR), EFS elicited relaxation of canine prostate strips relative to baseline tension. A weak biphasic response consisting of initial relaxation and subsequent contraction relative to baseline tension was observed in the human prostate strips exposed to similar conditions. The smooth muscle activity observed in the presence of GUA plus ATR was attributed to nonadrenergic, noncholinergic (NANC) nerve transmission. 10(-4) M L-NG-nitroarginine methylester (NAME) significantly increased EFS-elicited NANC smooth muscle activity both in human and canine prostates. L-arginine, 10(-2) M, reversed the effect of L-NAME in human and canine prostates. Sodium nitroprusside, 10(-4) M, a donor of NO, caused relaxation of both human and canine prostates. The mean magnitude of the relaxant response/cross-sectional area in human prostate (2.64 +/- 0.4 g/cm2) was significantly greater than in the canine prostate (1.09 +/- 0.17 g/cm2) (P < 0.005).

CONCLUSIONS

These results provide compelling evidence that NO plays a role in mediating contractile function of human and canine prostates.

Coexistence of nitric oxide synthase, tyrosine hydroxylase and vasoactive intestinal polypeptide in human penile tissue--a triple histochemical and immunohistochemical study

Recently, nitric oxide (NO) has been believed to act as a neuronal messenger to mediate penile erection. In the present study using human penile tissue, we investigated the coexistence of neuronal NO synthase (NOS), tyrosine hydroxylase (TH) and vasoactive intestinal polypeptide (VIP) by a triple staining method using NADPH diaphorase (ND) staining, a specific histochemical marker of neuronal NOS, and immunohistochemical staining for TH and VIP. Numerous ND-positive nerve fibers and TH-containing fibers were seen in axon bundles, but their distributions were different. Only a few axons in the bundles showed VIP immunoreactivity. Abundant fine varicose nerve terminals innervating cavernous smooth muscles and deep and helicine arteries were observed. The proportion of fibers showing TH-immunoreactivity in ND-positive terminals in the cavernous space was about 25%, and that of VIP was about 40%. Vasoactive intestinal polypeptide may act as a coworker in these fibers both in cavernous trabeculae and around arteries, as about 40% of NOS-containing fibers also showed VIP immunoreactivity. The physiological significance of the colocalization of TH and NOS is unclear, and further studies are required to know the physiological significance of the colocalization of NOS and other neurotransmitters in penile tissue.

Localization of nitric oxide synthase in spinal nuclei innervating pelvic ganglia

We employed retrograde axonal tracing techniques and nitric oxide synthase (NOS) and choline acetyltransferase (ChAT) immunohistochemistry to identify NOS-containing neuronal populations within the lumbosacral spinal cord and determine whether these project to the major pelvic ganglion in the adult male Sprague-Dawley rat. Immunohistochemical localizations of NOS included neurons situated at the L5 to S2 segments of the spinal cord, which corresponded to the sacral parasympathetic nucleus. Another prominent locus for NOS was a group of neurons identified in the L1 segment corresponding to the dorsal commissural nucleus. These regions correlated directly with preganglionic parasympathetic and sympathetic neuronal origins, respectively, which were established with ChAT colocalizations. Retrograde tracing verified the projection of these neurons to the pelvis. Additional neuronal localizations of NOS were observed throughout the intermediolateral cell column, involving the superficial laminae of the dorsal horn, in the region surrounding the central canal and occasionally in the medial area of the ventral horn. These results indicate that the regulation of pelvic visceral activity may involve NO-based neuronal mechanisms operating at the level of the lumbosarcal spinal cord.

A large proportion of pelvic neurons innervating the corpora cavernosa of the rat penis exhibit NADPH-diaphorase activity

Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, which indicates the presence of neural nitric oxide synthase, the enzyme responsible for the generation of nitric oxide, was used in combination with retrograde labelling methods to determine, in whole-mounts and sections of rat major pelvic ganglia, whether neurons destined for the penile corpora cavernosa were able to produce nitric oxide. In whole-mount preparations of pelvic ganglia, among the 607 +/- 106 retrogradely labelled neurons innervating the penile corpora cavernosa, 84 +/- 7% were NADPH-diaphorase-positive, 30 +/- 7% of which were intensely histochemically stained. In serial sections of pelvic ganglia, out of a mean count of 451 retrogradely labelled neurons, 65% stained positively for NADPH-diaphorase. An average of 1879 +/- 363 NADPH-diaphorase positive cell bodies was counted in the pelvic ganglion. In the major pelvic ganglion, neurons both fluorescent for Fluorogold or Fast Blue and intensely stained for NADPH-diaphorase were consistently observed in the dorso-caudal part of the ganglia in the area close to the exit of the cavernous nerve and within this nerve. This co-existence was much less constant in other parts of the ganglion. In the rat penis, many NADPH-diaphorase-positive fibres and varicose terminals were observed surrounding the penile arteries and running within the wall of the cavernous spaces. This distribution of NADPH-diaphorase-positive nerve cells and terminals is consistent with the idea that the relaxation of the smooth muscles of the corpora cavernosa and the dilation of the penile arterial bed mediated by postganglionic parasympathetic neurons is attributable to the release of nitric oxide and that nitric oxide plays a crucial role in penile erection.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide synthase activity in the human urogenital tract

Nitric oxide (NO) has been suggested as a nonadrenergic non-cholinergic neurotransmitter in the urogenital tract and has previously been shown to have a smooth muscle relaxing effect in the urogenital organs both in various animals and in humans. It has been shown that NO is a mediator of the erection and the dilatation of the bladder neck and urethra. The aim of the study was to analyse nitric oxide synthase (NOS) activity in the human urogenital tract. NOS activity was measured by the conversion of L-[U-14C] arginine to L-[U-14C] citrulline. In the upper urinary tract there was Ca(2+)-dependent NOS activity in the renal pelvis, but no significant NOS activity could be found in the ureter. In the lower urinary tract we found high Ca(2+)-dependent NOS activity in the urethra, intermediate activity in the bladder neck and comparatively low activity in the detrusor muscle. In the male genital tract the testis and epididymis had no significant NOS activity. The vas deferens, prostate, seminal vesicle and corpus cavernosum were found to have high levels of Ca(2+)-dependent NOS activity. Ca(2+)-independent NOS activity was not obtained in the urogenital tract. Our results correspond well with previous functional studies indicating NO to be an important nerve-induced mediator of erection and in the micturition reflex, but also suggest that NO may be involved in several other functions in the human urogenital tract.

Neuronal nitric oxide synthase is localized in extrinsic nerves regulating perireceptor processes in the chemosensory nasal mucosae of rats and humans

Nitric oxide synthase is the enzyme responsible for the production of the free radical gas nitric oxide, which has been implicated as an intercellular messenger in both the central and peripheral nervous systems. Immunoreactivity for nitric oxide synthase is often coincident with the histochemical demonstration of NADPH-diaphorase activity. Using an antibody to the neuronal form of nitric oxide synthase and a histochemical technique for NADPH-diaphorase, we have compared the localization of immunoreactivity and histochemical reaction product in the nasal mucosae of rats and humans. Immunoreactivity for neuronal nitric oxide synthase was localized in the extrinsic perivascular innervation of the olfactory and vomeronasal mucosae of rats and in the olfactory mucosa of humans. In the rat nasal mucosa, specific groups of glands were also innervated; the density of nitrinergic innervation varied among them, with vomeronasal glands and posterior glands of the nasal septum being the most densely innervated. In contrast, NADPH-diaphorase activity was present in olfactory, vomeronasal, and septal organ receptor neurons in rats and in olfactory receptor neurons in humans as well as in numerous nerve fibers, glands, and surface epithelial cells. The localization of neuronal nitric oxide synthase in extrinsic perivascular and periglandular nerve fibers suggests that nitric oxide may modulate the perireceptor processes of local blood flow and mucus secretion that influence the access to and clearance of chemical stimuli from rat and human chemosensory mucosae.