Patients with lower motor spinal cord lesion: a decrease of vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P, but not neuropeptide Y and somatostatin-immunoreactive nerves in the detrusor muscle of the bladder

The role of vasoactive intestinal polypeptide and pituitary adenylate cyclase-activating polypeptide in the neural pathways controlling the lower urinary tract

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are expressed in the neural pathways regulating the lower urinary tract. VIP-immunoreactivity (IR) is present in afferent and autonomic efferent neurons innervating the bladder and urethra, whereas PACAP-IR is present primarily in afferent neurons. Exogenously applied VIP relaxes bladder and urethral smooth muscle and excites parasympathetic neurons in bladder ganglia. PACAP relaxes bladder and urethral smooth muscle in some species (pig) but excites the smooth muscle in other species (mouse). Intrathecal administration of VIP in cats with an intact spinal cord suppresses reflex bladder activity, but intrathecal administration of VIP or PACAP in rats enhances bladder activity and suppresses urethral sphincter activity. PACAP has presynaptic facilitatory effects and direct excitatory effects on lumbosacral parasympathetic preganglionic neurons. Chronic spinal cord transection produces an expansion of VIP-IR (cats) and PACAP-IR (rats) in primary afferent axons in the lumbosacral spinal cord and unmasks spinal excitatory effects of VIP on bladder reflexes in cats. Intrathecal administration of PACAP6-38, a PAC1 receptor antagonist, reduces bladder hyperactivity in chronic spinal-cord-injured rats. These observations raise the possibility that VIP or PACAP have a role in the control of normal or abnormal voiding.

Distribution of neuropeptide Y-containing nerves in the neurogenic and non-neurogenic detrusor

OBJECTIVE

To evaluate the role of neuropeptide Y in the detrusor of patients with neurogenic detrusor overactivity (NDO), as it has an important role in the neural regulation of the lower urinary tract by exerting differential effects on the release of cholinergic and adrenergic transmitters via autoinhibition and heterosynaptic interactions.

MATERIALS AND METHODS

Detrusor biopsies were obtained from 38 patients; 31 had video-urodynamically verified NDO, caused by meningomyelocele in 17 or spinal cord injury in 14. Seven had stress urinary incontinence (SUI) and this group served as a control. All specimens were fixed, paraffin wax-embedded, sectioned and stained with a monoclonal antibody against neuropeptide Y and a general nerve marker protein-gene-product 9.5 (PGP 9.5). The number of PGP 9.5- and neuropeptide Y-containing nerves was quantified by a standardized evaluation using image-analysis software.

RESULTS

The median (range) number of neuropeptide Y-containing nerves in the neurogenic detrusor, at 0.273 (0.126-0.639) per muscle cell nucleus (MCN), was significantly lower (P = 0.014) than that in patients with SUI, at 0.383 (0.267-0.728). In the neurogenic detrusor the number of PGP 9.5-positive nerves, at 0.278 (0.054-0.641)/MCN was also lower (P = 0.111) than in patients with SUI, at 0.368 (0.258-0.497). The ratio of neuropeptide Y to PGP 9.5 counts per biopsy did not differ between the groups (P = 0.628).

CONCLUSIONS

The number of PGP 9.5-positive nerves was not significantly and the number of neuropeptide Y-containing nerves was significantly reduced in patients with NDO. This may have been caused by transynaptic nerve degeneration of the detrusor, as described by in patients with spinal cord injury. As neuropeptide Y inhibits the contractile response of the detrusor the reduction of neuropeptide Y-containing nerves may play a role in the development and persistence of DO.

Alterations in neurogenically mediated contractile responses of urinary bladder in rats with diabetes

Diabetic bladder dysfunction (DBD) is among the most common and bothersome complications of diabetes mellitus. Autonomic neuropathy has been counted as the cause of DBD. In the present study, we compared the alterations in the neurogenically mediated contractile responses of urinary bladder in rats with streptozocin-induced diabetes, 5% sucrose-induced diuresis, and age-matched controls. Male Sprague-Dawley rats were divided into three groups: 9-wk diabetic rats, diuretic rats, and age-matched controls. Micturition and morphometric characteristics were evaluated using metabolic cage and gross examination of the bladder. Bladder detrusor muscle strips were exposed to either periodic electrical field stimulation (EFS) or to EFS in the presence of atropine, alpha,beta-methylene adrenasine 5'-triphosphate, or tetrodotoxin. The proportions of cholinergic, purinergic, and residual nonadrenergic-noncholinergic (NANC) components of contractile response were compared among the three groups of animals. Diabetes caused a significant reduction of body weight compared with diuresis and controls, although the bladders of diabetic and diuretic rats weighed more than the controls. Both diabetes and diuresis caused significant increase in fluid intake, urine output, and bladder size. Diabetes and diuresis caused similarly increased response to EFS and reduced response to cholinergic component compared with controls. However, the purinergic response was significantly smaller in diuretic bladder strips compared with controls but not in diabetic rats. A residual NANC of unknown origin increased significantly but differently in diabetics and diuretics compared with controls. In conclusion, neurogenically mediated bladder contraction is altered in the diabetic rat. Diabetic-related changes do not parallel diuretic-induced changes, indicating that the pathogenesis of DBD needs further exploration.

The tachykinin NK-2 receptor antagonist SR48968 does not block noncholinergic contractions in unstable human bladder

Concentration-response curves to acetylcholine, and responses to electrical field stimulation (EFS) were compared in detrusor muscle strips, from control patients and those with idiopathic detrusor instability (IDI). Responses were similar in both groups. However, atropine abolished responses to EFS in 80% of control but only 33% of IDI patients (P>0.05), with the residual atropine-resistant response in most IDI patients abolished by tetrodotoxin. The post-atropine residual response was unaffected by the tachykinin NK-2 receptor antagonist SR48968. Despite the known existence of NK-2 receptors in the human detrusor, there was no evidence for tachykinin contribution to EFS-induced contractions.

Enhancement of neurokinin A-induced smooth muscle contraction in human urinary bladder by mucosal removal and phosphoramidon: relationship to peptidase inhibition

Neurokinin A (NKA) is potent in contracting the human detrusor muscle. Here, we have investigated whether these contractile responses are influenced by the presence of the mucosa, by the peptidase inhibitor phosphoramidon or by possible modulators, prostaglandins and nitric oxide. Contractile responses to neurokinin A were unaffected by indomethacin or N-omega-nitro-L-arginine, but were significantly reduced in strips containing mucosa. Phosphoramidon, an inhibitor of neutral endopeptidase 24.11 (neprilysin, CD10), was ineffective at 10 microM, but at 100 microM, significant increase in the maximum response was achieved by neurokinin A in detrusor strips with and without mucosa. In immunohistochemical studies, neutral endopeptidase immunoreactivity occurred in peripheral nerve trunks in the detrusor and in a fibrous meshwork in the subepithelial lamina propria. Our data indicate that neutral endopeptidase is present in bladder mucosa and detrusor, and support the concept that this metalloprotease and/or related enzymes are important in regulating the actions of tachykinins.

Functional anatomy of the organs of micturition

The anatomy of the organs of micturition has been the subject of study for nearly 150 years. As a result of advances in techniques and methods of clinical and research investigation, studies over the past three decades have intensified and have been increasingly directed at the functional implications and significance of organ anatomy and structure. This has led to revision of many traditional ideas about micturition and the development of new viewpoints and modalities for study of its disorders. This article summarizes the evolution of our thinking and understanding of the functional anatomy of the bladder and urethra over the years, and suggests possible directions for continued clinical study and investigation.

The norepinephrine tissue concentration and neuropeptide Y immunoreactivity in genitourinary organs of the spontaneously hypertensive rat

Tissue concentration of norepinephrine and neuropeptide-Y immunoreactivity (NPY-IR) were measured in the urinary bladder, urethra, prostate and corpus cavernosum of the spontaneously hypertensive rat, as well as the normotensive Wistar-Kyoto rat. The results showed significantly increased tissue norepinephrine concentrations in the urinary bladder, urethra and prostate of the spontaneously hypertensive rat when compared to those of the normotensive rat (hypertensive, n = 18: 18.3 +/- 2.1, 14.9 +/- 1.7, 22.6 +/- 2.3 vs. normotensive, n = 18: 11.2 +/- 1.9, 10.4 +/- 1.3, 16.7 +/- 2.4 nmol/g tissue, respectively, P < 0.05 in each case). No difference was noted in the cavernosal tissue (hypertensive, n = 18: 11.3 +/- 1.6 vs. normotensive, n = 18: 10.1 +/- 1.8 nmol/g tissue, P > 0.01). Correspondingly, tissue NPY-IR was significantly increased in the bladder, urethra and prostate tissue of the spontaneously hypertensive rat (hypertensive, n = 18: 39.7 +/- 5.6, 25.3 +/- 3.4, 31.5 +/- 2.8 vs. normotensive, n = 18: 27.4 +/- 3.1, 18.6 +/- 2.7, 24.2 +/- 3.2 pmol/g tissue, respectively, P < 0.05 in each case). Again, no significant difference was observed in the cavernosal tissue (hypertensive, n = 18: 15.9 +/- 2.2 vs. normotensive, n = 18: 14.8 +/- 2.6 pmol/g tissue, P > 0.01). It is therefore concluded that increased tissue concentration of norepinephrine and NPY-IR were present in the urinary bladder, urethra and prostate of the spontaneously hypertensive rat. The significance of such biochemical findings needs further investigation but may suggest increased sympathetic innervation or activity. On the contrary, no corresponding changes were observed in the corpus cavernosum of the hypertensive rat.

Age-associated changes in detrusor sensory function in women with lower urinary tract symptoms

This study examined changes in bladder sensation which occur with age in women. 1381 women (age range 20-95 years, mean 54.9) with symptoms of lower urinary tract dysfunction underwent urodynamic study. The bladder capacity at which they first became aware of the desire to void was taken as a quantitative measure of bladder sensation. Maximum bladder capacity fell in the eighth and ninth decades (H = 95.84, df = 7, P = 0.00), but by contrast bladder capacity at first desire to void rose progressively in association with age, both in the group as a whole (H = 17.13, df = 7, P = 0.017) and in a subgroup with detrusor instability (n = 952, H = 15.42, df = 7, P = 0.032). This rise in capacity points to a decrease in bladder sensation in association with age. This is not due to neurological disease, anti-muscarinic drugs or oestrogens, as the median capacity at first desire to void of these three subgroups did not differ significantly from that of the group as a whole.

Expression and characterization of preproVIP derived peptides in the human male urogenital tract

Expression of the gene sequence encoding vasoactive intestinal polypeptide (VIP) leads to the synthesis of a 170 amino acid precursor molecule which can be processed to five fragments: preproVIP 22-79, peptide histidine methionine (PHM), or peptide histidine valine (PHV), preproVIP 111-122, VIP and preproVIP 156-170. Using region specific radioimmunoassays and antisera against the functional domains of the VIP precursor in combination with immunocytochemistry and chromatography, the localization, distribution and identity of the preproVIP derived peptides within the human male urogenital tract were investigated. Postmortem as well as fresh tissue specimens were used. All the preproVIP derived peptides were expressed and could be demonstrated in nerve fibres throughout the urogenital tract in close relation to the epithelial lining and in vascular as well as non-vascular smooth muscle. The VIP-related peptide containing fibres were most abundant in the prostate parenchyma and the seminal vesicle. Using double immunostaining, co-localization of the various preproVIP derived peptides could be evidenced. The fact that all preproVIP derived peptides are present in the urogenital tract, should be taken into consideration when the regulatory aspects of neuropeptides in physiological and pathophysiological functions are discussed.

CGRP-immunoreactive primary afferent nerve fibers in the rat urinary bladder: effects of dorsal rhizotomy and MK-801

A transection lesion of the suprasacral spinal cord results in a decreased density of calcitonin gene-related peptide (CGRP)-immunoreactive (I) primary afferent nerve fibers in the rat urinary bladder. The fiber density can be restored by postsurgical treatment with the N-methyl-D-aspartate receptor antagonist MK-801. We are attempting to determine the level of the primary afferent neuron at which MK-801 might have a restorative effect on CGRP immunostaining. Thus, the purpose of this study was to determine if MK-801 had a similar restorative effect on immunostaining for CGRP in bladder nerves after a direct lesion of the sacral afferent system, i.e., rhizotomy of the L6 and S1 dorsal roots. To assess the effect of the lesion, the mean length and number of bladder CGRP-I nerve fibers, as well as the number of CGRP-I perikarya in the L6 and S1 dorsal root ganglia (DRG), were measured following bilateral L6 and S1 dorsal rhizotomies. Both the mean length and the numbers of CGRP-I bladder fibers were significantly decreased by the lesion. However, the number of CGRP-I primary afferent perikarya in the L6 and S1 DRG was unchanged from control values. Rats which received rhizotomies and subsequent treatment with MK-801 did not exhibit restoration of the density of CGRP-I bladder fibers nor an alteration in the number of CGRP-I primary afferent perikarya. These data suggest that MK-801-induced restoration of bladder CGRP-I primary afferent nerve fibers may rely on an intact central process.

Morphine-induced modulation of calcitonin gene-related peptide levels

Calcitonin gene-related peptide (CGRP) is a novel calcium-modulatory product of the gene that encodes for calcitonin. Acute administration of morphine decreases levels of CGRP in rat corpus striatum. Tolerance to morphine did not alter the levels of CGRP in any brain region or in the spinal cord of the rat. CGRP did not alter the tolerance to the antinociceptive effects of morphine. Chronic naltrexone increased the levels of CGRP in the hypothalamus. Concurrent chronic administration of naltrexone plus morphine raised the levels of CGRP in the medulla, midbrain, and spinal cord. CGRP enhances naloxone-precipitated withdrawal jumping in mice. In rats, during withdrawal the levels of CGRP were tripled in the corpus striatum and significantly reduced in the hippocampus and hypothalamus. In the corpus striatum, CGRP enhances forskolin-stimulated cyclic adenosine monophosphate (cAMP) accumulation when such accumulation is suppressed (as with the chronic opiate administration), but conversely depresses forskolin-stimulated cAMP accumulation under normal conditions (as with chronic vehicle administration). These data are consistent with the hypothesis that CGRP acts as a modulatory peptide in opiate-sensitive systems and tonic opioid control of CGRP levels exists in brain.

Loss of sensory neuropeptides in the obstructed human bladder

This is the first investigation of alterations in the innervation of the obstructed human bladder by nerves containing neuropeptides. The patient groups studied were those with stable detrusor function, those with unstable detrusor function, and those presenting with acute retention of urine. Specimens of bladder tissue were taken from the lateral wall of the bladder below the peritoneal reflection. A total of 23 patients was studied (control, n = 4; acute retention, n = 5; stable obstruction, n = 5; unstable obstruction, n = 9). Substance P, calcitonin gene-related peptide and vasoactive intestinal polypeptide levels in the bladder were quantified by immunoassay. The density of innervation of the bladder detrusor by nerves containing these neurotransmitters and by those containing neuropeptide Y and somatostatin was assessed using both semiquantitative and quantitative immunohistochemical techniques. A reduction in the density of innervation by vasoactive intestinal polypeptide, calcitonin gene-related peptide, substance P and somatostatin-immunoreactive but not neuropeptide Y-immunoreactive nerve fibres was shown in the obstructed bladder. These findings, combined with the significant reduction in substance P content of the obstructed bladder and in particular of the acute retention bladder, indicate that there may be an afferent nerve dysfunction resulting from prostatic bladder outflow obstruction.