Hiroya Mizusawa

INTRAVESICAL OXYHEMOGLOBIN INITIATES BLADDER OVERACTIVITY IN CONSCIOUS, NORMAL RATS

PURPOSE To investigate whether intravesical oxyhemoglobin, a nitric oxide scavenger, changes bladder activity in normal rats. MATERIALS AND METHODS Oxyhemoglobin was given intravesically at different concentrations to conscious, female Sprague-Dawley rats undergoing continuous cystometry. RESULTS Intravesical oxyhemoglobin increased bladder activity in a concentration-dependent way. At a concentration of 2.5 x 10-4 M (n = 8), micturition pressure (p <0. 01), basal pressure (p <0.01), and residual volume (p <0.05) increased, and bladder capacity (p <0.001) and micturition volume (p <0.001) decreased. The effect of oxyhemoglobin was reduced or abolished by L-arginine (200 mg./kg.-1), given intra-arterially near the bladder, and was enhanced by the guanylate cyclase inhibitor, ODQ (0.5 and 1 mg./kg.-1). The K+ channel opener, ZD6169 100 ng.ml. -1, given intravesically for 1 hour prior to instillation of oxyhemoglobin, reduced or completely prevented the bladder activity induced by oxyhemoglobin. CONCLUSIONS Intravesical oxyhemoglobin induces bladder overactivity, probably by interfering with nitric oxide (NO) generated in the urothelium or suburothelially. NO may be involved in the regulation of the threshold for afferent firing in the bladder.

Morphological and functional in vitro and in vivo characterization of the mouse corpus cavernosum.

In normal mice, the distribution of adrenergic, cholinergic, some peptidergic, and neuronal nitric oxide synthase (nNOS)‐containing nerves were investigated. Functional in vitro correlates were obtained. An in vivo model was developed in which erectile haemodynamics in response to drugs or nerve‐stimulation were studied. Immunoreactivities for vesicular acetylcholine transporter protein (VAChT), nNOS‐, and vasoactive intestinal polypeptide (VIP), co‐existed in nerve fibres and terminal varicosities. Immunoreactivities for neuropeptide Y (NPY) and tyrosine hydroxylase (TH) were found in the same nerve structures. Chemical sympathectomy abolished TH‐ and NPY‐IR nerve structures in cavernous smooth muscle bundles. The distribution of calcitonin gene‐related peptide (CGRP)‐, nNOS‐, VAChT‐ and VIP‐IR nerve structures was unchanged. In endothelial cells of the central and helicine arteries, veins and venules, intense immunoreactivity for endothelial NOS (eNOS) was observed. No distinct eNOS‐IR cells were found lining the cavernous sinusoids. In vitro, nerve‐induced relaxations were verified, and endothelial NO/cyclic GMP‐mediated relaxant responses were established. VIP and CGRP had small relaxant effects. A functioning adenylate cyclase/cyclic AMP pathway was confirmed. Neuronal excitatory responses were abolished by prazosin, or forskolin. VIP and CGRP counteracted contractions, whereas NPY and scopolamine enhanced excitatory responses. In vivo, erectile responses were significantly attenuated by L‐NAME (50 mg kg−1) and facilitated by sildenafil (200 μg kg−1). It is concluded that the mouse is a suitable model for studies of erectile mechanisms in vitro and in vivo.

alpha-Melanocyte stimulating hormone and oxytocin induced penile erections, and intracavernous pressure increases in the rat.

PURPOSE alpha-Melanocyte stimulating hormone (alpha-MSH; Fluka Chemie AG, Geneva, Switzerland) and oxytocin induce erection in rats after intracerebroventricular administration. We studied possible interactions of alpha-melanocyte stimulating hormone with mechanisms pertaining to oxytocin or nitric oxide. MATERIALS AND METHODS We used 78 anesthetized male Sprague-Dawley rats. Catheters were implanted in the lateral cerebral ventricle or into the subarachnoid space at L6 to S1. Intracavernous pressure was documented and arterial blood pressure was directly measured. RESULTS Intracerebroventricular alpha-MSH (3 microg.) produced a mean of 2.6 +/- 0.6 erectile responses (p <0.05) with a mean duration of 3.4 +/- 1.1 minutes (p <0.05). Mean peak intracavernous pressure was 114 +/- 8 cm. water. An intracerebroventricular dose of 100 microg. N-nitro-L-arginine-methyl ester HCl (Sigma Chemical Co., St. Louis, Missouri) given in intracerebroventricular fashion abolished alpha-MSH induced erectile responses, whereas intracerebroventricular administration of 500 ng. of the oxytocin receptor antagonist l-deamino, 2-D-Tyr(Oet), 4-Thr, 8-Orn-OT (Ferring AB, Malmö, Sweden) had no effect. Intracerebroventricular oxytocin (30 ng.) induced a mean of 3.2 +/- 0.9 erectile responses (p <0.05) with a mean peak intracavernous pressure of 81 +/- 8 cm. water and a mean duration of 3.3 +/- 1.1 minutes. Intrathecal alpha-MSH (3 microg.) did not produce any erectile responses, whereas a mean of 5.7 +/- 0.9 responses (p <0.001) with a mean peak intracavernous pressure of 142 +/- 8 cm. water and mean duration of 5.0 +/- 1.3 minutes was obtained with 30 ng. oxytocin intrathecally. Responses induced by intrathecal oxytocin were abolished by 100 microg. N-nitro-L-arginine-methyl ester HCl intrathecally. CONCLUSIONS We confirmed by monitoring intracavernous pressure and blood pressure that supraspinal erectile responses induced by alpha-melanocyte stimulating hormone involve effects mediated by nitric oxide but are independent of oxytocinergic mechanisms. At the spinal level oxytocin produces erectile responses involving nitric oxide. alpha-Melanocyte stimulating hormone does not seem to have a spinal site of action.

A rat model for investigation of bladder dysfunction associated with demyelinating disease resembling multiple sclerosis

Myelin basic protein (MBP) can be used as an antigen for inducing experimental allergic encephalomyelitis (EAE). In various studies, EAE animals have been used as an experimental model of demyelinating diseases. The aim of this study was to determine whether EAE, induced by MBP in rats, can be useful for investigation of bladder dysfunction associated with demyelinating disease. Female Lewis rats were used. In Study 1, the time course of behavioral and cystometric changes were observed consecutively after MBP sensitization. In Study 2, the correlations between behavioral, cystometric, and histologic abnormalities were studied. The degree of paralysis and histologic findings were evaluated. In Study 1, transient hind limb paralysis was observed in all rats. Cystometric findings were characterized by three different patterns: 1) detrusor areflexia (DA), 2) detrusor hyperactivity (DH), and 3) normal. Ten (77%) of the 13 rats given MBP showed bladder dysfunction, including DA (seven), DA/DH (two) and DH (one). Study 2 showed DA in 10 rats, DH in one, and normal findings in nine animals. The difference in degree of paralysis between the DA and the cystometrically normal animals was statistically significant (P < 0.01). The mean value of the degree of inflammation in the spinal cord (L6–S1) in the DA group was significantly (P < 0.05) higher than that in the cystometrically normal group. The degrees of paralysis and spinal inflammation were weakly correlated (R = 0.47, P = 0.05). The present rat model seems useful for studies of bladder dysfunction associated with spinal myelitis/demyelinating diseases. Neurourol. Urodynam. 19:689–699, 2000.

Squamous cell carcinoma in the renal pelvis of a horseshoe kidney.

Abstract We report a rare case of squamous cell carcinoma in the renal pelvis of a horseshoe kidney. An 80‐year‐old woman was referred to the National Nagano Hospital for the examination of occult blood in her urine. Microscopic hematuria was found, but pyuria was not seen. Computed tomography and magnetic resonance imaging showed a mass in the left renal pelvis of the horseshoe kidney. No renal stone or hydronephrosis was found. Cytopathological examination in the voided urine specimen was positive. Left nephroureterectomy with the splitting of the isthmus of the horseshoe kidney was performed without renal pedicle clamping using a microwave tissue coagulator. No bleeding was encountered after separating the isthmus. A final pathological diagnosis of squamous cell carcinoma with a tumor thrombus was made. Lymph node metastasis had developed and rapidly progressed and the patient died of disseminated malignancy 4 months after the operation.

Effect of apomorphine on intracavernous pressure and blood pressure in conscious, spinalized rats

Apomorphine, given subcutaneously (s.c.), induces erection and bladder overactivity in rats through stimulation of dopamine (D1- and D2-like) receptors in the central nervous system. In paraplegic patients, apomorphine was reported to cause bladder overactivity. This suggests that apomorphine may have a spinal site of action also for stimulation of erection. The present study was initiated to evaluate the effect of apomorphine on erectile function in spinalized rats. Apomorphine (100 μg/kg, s.c.) was given to awake, unrestrained male Sprague-Dawley rats (300 g) with or without spinal cord injury, made at the Th 8 level 2 weeks before the experiment. Intracavernous pressure changes from baseline were evaluated as time to first response to apomorphine (TFR; sec), number of phasic pressure changes in the first 30 min (PP30), duration (D; sec) of the phasic pressure changes, the amount of increase in tonic peak pressure (TPP; cmH2O), and burst peak pressure (BPP; cmH2O). Blood pressure (cmH2O) was recorded via an intra-arterial catheter. Apomorphine, 100 μg/kg, caused no significant differences in TFR (217.8 vs 271.2), PP30 (6.4 vs 6.5), D (38.9 vs 37.6.), TPP (51.0 vs 54.0) and BPP (128.9 vs 160.4) between normal (n=8) and spinalized rats (n=6). However, blood pressure decreased significantly more in spinalized than in normal animals (17.7 vs 43.3; P<0.05). The results suggest that both in normal rats, and in rats with spinal cord injury, apomorphine given s.c., can produce erection. This finding supports the use of apomorphine for treatment of erectile dysfunction in paraplegia patients. However, due consideration should be given to possible decreases in blood pressure.

Enhancement of apomorphine-induced penile erection in the rat by a selective alpha(1D)-adrenoceptor antagonist.

Effects of A‐322312 (α1B‐adrenoceptor (AR) antagonist), A‐119637 (α1D‐AR antagonist), prazosin (non‐selective α1‐AR antagonist), and yohimbine (α2‐AR antagonist) were studied in rat corpus cavernosum (CC) and cavernous artery (Acc) preparations. Effects of intracavernous (i.c.) or intraperitoneal (i.p.) administration of α1‐AR antagonists on apomorphine‐induced erections were investigated. A‐119637 attenuated electrically induced contractions in isolated CC (−logIC50; 8.12±0.15), and relaxed noradrenaline (NA)‐contracted preparations by more than 90% at 10−7 M. At the same concentration, the −logEC50 value for NA in Acc was altered from 6.79±0.07 to 4.86±0.13. In the CC and Acc, prazosin similarily inhibited contractile responses. Inhibitory effects of A‐322312 (10−7 M) in electrically activated CC were 32.3±5.1%, whereas no effect on concentration‐response curves for NA was observed in the Acc. Yohimbine (10−8 M and 10−7 M), enhanced electrically‐induced contractions in isolated CC by 20 to 50%. At 10−6 M, inhibitory effects of yohimbine were obtained. A‐119637 (0.3 μmol kg−1, i.p.) tripled the number of erections, and produced a 6 fold increase in the duration of apomorphine‐induced erectile responses. A‐322312, prazosin, or yohimbine did not enhance erections induced by apomorphine. None of the α1‐AR antagonists significantly increased ICP upon i.c. administration. Decreases in blood pressure were seen with A‐119637 and prazosin. The present findings show that there is a functional predominance of the α1D‐AR subtype in the rat erectile tissue, and that blockade of this receptor facilitates rat penile erection induced by a suboptimal dose of apomorphine.