Dual modulation of urinary bladder activity and urine flow by prostanoid EP3 receptors in the conscious rat.

BACKGROUND AND PURPOSE: Cyclooxygenase inhibitors function to reduce levels of prostaglandin E(2) (PGE(2)) and are broadly efficacious in models of bladder overactivity. We therefore investigated a regulation of urinary bladder function in conscious rats by modulation of the EP(3) receptor for PGE(2). EXPERIMENTAL APPROACH: The activity of the EP(3) receptor agonist GR63799X, and EP(3) receptor antagonists, CM9 and DG041, at recombinant EP(3) receptors was evaluated in vitro. In vivo, intraduodenal dosing during conscious, continuous-filling cystometry of spontaneously hypertensive rats was utilized to determine the urodynamic effect of EP(3) receptor modulation. KEY RESULTS: GR63799X dose-dependently (0.001-1 mg x kg(-1)) reduced bladder capacity, as indicated by a reduction in both the micturition interval and volume of urine per void. In contrast, CM9 (10 and 30 mg x kg(-1)) and DG041 (30 mg x kg(-1)) enhanced bladder capacity, as indicated by significantly longer micturition intervals and larger void volumes. CM9 and DG041 inhibited the responses to GR63799X supporting the in vivo activity of these pharmacological agents at the EP(3) receptor. In addition to its effect on bladder capacity, GR63799X increased endogenous urine production. Intra-arterial infusion of saline mimicked the enhancement of urine flow observed with GR63799X, and the response was inhibited by CM9. CONCLUSIONS AND IMPLICATIONS: These data support the EP(3) receptor as a modulator of urinary bladder activity in the conscious rat, and in addition, indicate a role for EP(3) receptor activity in regulating urine flow.

Potentiation by bradykinin and substance P of purinergic neurotransmission in urinary bladder.

PURPOSE: The higher than normal levels of substance P (SP) and the kinins in patients suffering from interstitial cystitis suggest that they may contribute to the complex symptoms of the condition. The purpose of our experiments was to determine whether SP and bradykinin (BK) influence the excitatory motor innervation of the urinary bladder. MATERIALS AND METHODS: Strips of guinea pig urinary bladder were placed in isolated tissue baths, and the influence of SP and BK on contractions induced by transmural electrical stimulation and cholinergic and purinergic agonists was evaluated. RESULTS: Substance P and BK potentiated responses to the purinergic component of the neurogenic stimulation (that part of the contractile response that remains after treatment with atropine) and potentiated responses to exogenously applied adenosine triphosphate (ATP). The peptides did not potentiate the response to the cholinergic component of the nerve-induced contraction (that part of the neurogenic response that remains after desensitization of purinoceptors with alpha, beta-methylene ATP) nor responses to carbachol. The potentiating actions of SP and BK were reduced but not abolished by treatment with meclofenamic acid. CONCLUSIONS: Substance P and BK potentiate the neurogenic response of the bladder by influencing the purinergic component of the excitatory motor innervation, apparently at a postjunctional site. Prostaglandins may be involved in mediating some of the actions of these peptides.

Potentiation of purinergic neurotransmission in guinea pig urinary bladder by histamine.

Patients suffering from the inflammatory condition of interstitial cystitis frequently exhibit an increased number of mast cells in the bladder. To determine whether mast cell mediators have the potential to influence the neurogenic contraction of the bladder smooth muscle and thereby possibly contribute to the symptoms of interstitial cystitis, we examined the effects of histamine, a major inflammatory mediator of mast cell origin, on nerve- and agonist-induced contractions of in vitro strips of guinea pig urinary bladder. Histamine (10 microM.) potentiated by more than 50% the nerve-induced contraction of bladder strips evoked by field stimulation with 0.5 msec. pulses at 4 Hz. Because the neurogenic contraction of the bladder is mediated by at least two neurotransmitters, acetylcholine (ACh) and ATP, we examined the effects of histamine on each of these transmitters. Histamine potentiated responses to the purinergic component of the neurogenic response (that part of the neurogenic response that remains after treatment with atropine) and potentiated responses to exogenously applied ATP. Histamine did not potentiate the response to the cholinergic component of the neurogenic response (that part of the neurogenic response that remains after desensitization of purinoceptors with alpha, beta-methylene ATP) nor responses to carbachol, a cholinergic agonist. These results indicate that histamine potentiates the neurogenic response of the bladder by influencing the purinergic component, apparently at postjunctional sites.

Quantitative evaluation of spermatogenesis in mice following chronic exposure to cannabinoids.

In mice, chronic administration of crude marihuana extract (CME), delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) (50 mg kg-1 body weight for 15 and 35 days) impaired spermatogenesis at both mitotic and meiotic stages. Although the total number of step 7 spermatids was unaltered, mature spermatozoa recovered from the cauda epididymidis showed severe abnormalities in morphology. Body weight and sex organ weights were not affected markedly but the adrenal gland was hypertrophied. Leydig cell nuclear area was increased by CME and CBD and reduced by CBN. Cannabis deranges several stages of the spermatogenic cycle, most of the activity of the crude extract being attributable to CBN and CBD.

Biogenic amines and ascorbic acid in rat brain following steroid contraceptive treatment.

Chronic treatment with steroid contraceptive produced a decrease in dopamine and norepinephrine concentration in discrete brain areas and an increase in ascorbic acid level. We suggest that alteration in the level of biogenic amines by steroid contraceptive may have some functional correlation with the ascorbic acid concentration in rat brain.

Effect of the synthetic cannabinoid nabilone on spermatogenesis in mice.

Chronic treatment of mice with the synthetic cannabinoid nabilone (50 mg/kg, 3 times per week) reduced the number of pachytene spermatocytes. Nabilone did not affect other cell types in the testis or the sex organ weights. Nabilone tended to increase the number of abnormal spermatozoa, but this did not reach statistical significance. It is concluded that nabilone causes less testicular toxicity than the natural cannabinoids.

The effect of inhibitors of prostaglandin formation on contraction of the rat, rabbit and human vas deferens.

1. The rat vas deferens releases both PGE2 and PGF2 alpha under basal conditions in vitro but the human vas deferens synthesizes prostaglandins only when arachidonic acid is supplied exogenously. 2. The release of PGE2 and PGF2 alpha is augmented by alpha-adrenoceptor activation or by BaCl2, both of which cause contraction. 3. Release of PGE2 and PGF2 alpha is substantially inhibited by indomethacin 10 micrograms ml-1 which does not affect contraction. 4. Contraction is strongly inhibited by higher concentrations of indomethacin (50-80 micrograms ml-1). 5. It is concluded that the release of PGE2 and PGF2 alpha from the rat and human vas deferens is not correlated with contraction.

Interactive effects of chronic phencyclidine and delta 9-tetrahydrocannabinol on spermatogenesis in mice.

In this study, the combined effects of chronic phencyclidine (PCP) and delta 9-tetrahydrocannabinol on spermatogenesis in mice were examined. Mice were treated with THC (50 mg/kg, PO) and PCP (15 mg/kg, IP) alone or in combination for 16 days and with PCP alone for 35 days. THC had a significant effect on spermatogenesis and decreased the number of all germinal cells. PCP, on the other hand, affected all germinal cells except spermatids after 35 days of treatment. Combination of THC and PCP treatment caused a significant decrease in resting and pachytene spermatocytes. Similarly, combination of these two drugs caused a significant increase in cauda epididymal abnormal sperms. These results suggest that THC and PCP may cause greater disruption in spermatogenesis when they are abused together.

Body fluid and hematologic changes in the toad exposed to 48 h of simulated high altitude.

Body fluid and hematologic changes were found in three groups of adult male toads that had been exposed to 48 h of continuous simulated altitudes of 12,000, 18,000, and 24,000 ft, respectively. Erythrocyte counts and hematocrit ratios were increased significantly in all the high-altitude-exposed animals compared with the control group of animals kept at sea level, whereas the hemoglobin concentrations were significantly increased only in the 18,000- and 24,000-ft-exposed animals. Exposure to high altitude generally caused a reduction of plasma volume, blood volume, extracellular fluid volume, and total body water. These reductions were markedly lower in the animals exposed to 24,000 ft. These simulated high-altitude effects on body fluids and hematology in the toad (Bufo melanostictus) were compared with those of the rat, birds, and humans acutely acutely exposed at various high altitudes and were found to be qualitatively similar.

Studies on the erythropoietic effect of testis of toad at a simulated high altitude (hypoxic exposure).

Sham operated control toads (non castrated) have shown increased activity in regard to the hematological parameters in comparison to the castrated toads kept under simulated hypoxic condition. Injection of plasma from sham operated control toads exposed to hypoxic stimulation initiates erythropoiesis in starved toads, whereas plasma from castrated exposed to the same hypoxic stimulation failed to do so. It can be suggested that in toad, testis is the only organ responsible for controlling erythropoiesis by secreting certain substance in the blood, which acts as erythropoietic stimulating factor (ESF), and the production of this factor was found to increase in response to the hypoxic stimulation in order to combat under low atmospheric condition.

A histochemical study of leucine amino peptidase activity in the testes of immature and mature guinea-pigs.

The distribution of the enzyme leucine amino peptidase (LAP) has been studied histochemically in immature and mature guinea-pig testes. Immature guinea-pig testis showed a very feeble LAP activity, while in mature ones strong LAP activity was noted. The present communication indicates a direct relationship between the activity of the enzyme LAP and sexual maturation.

Augmentation of luteinizing hormone action by prostaglandin E2 in the prevention of antispermatogenic effect of indomethacin. Indomethacin & spermatogenesis.

Administration of indomethacin exhibited antigonadal action by inhibiting the Leydig cells, sex-accessories and spermatocyte-spermatid conversion process. Administration of PGE2 or PGF2 alpha had no effect on Leydig cell nuclear volume or accessory organ weights, but PGE2 had a restorative effect on the efficiency of meiosis, although at a statistical non-significant level. Administration of LH to indomethacin treated rats restored the accessories fully with a non-significant effect on the yield of step-7 spermatids from meiosis. Simultaneous administration of indomethacin, LH and PGE2 (but not PGF2 alpha) restored both sex-accessories and spermatid number to the level of vehicle injected controls.

Possible alpha-adrenergic involvement in nicotine induced alteration of spermatogenesis in rat.

Nicotine caused a fall in primary spermatocyte number together with a retardation of spermatocyte to spermatid conversions process. These effects of nicotine were possibly secondary to increased activity of adrenomedullary catecholamines, since the antispermatogenic effect of nicotine was prevented by phentolamine, a known blocker of catecholamine action at the alpha-receptor level.

Andrenogonadal interactions in nicotine-induced alteration of steroidogenesis in male rat.

Chronic nicotine administration in larger doses inhibits steroidogenesis in testis. This inhibition is possibly secondary to increased adrenomedullary norepinephrine activity, since the anti-steroidogenic effect of nicotine can be prevented by alpha-adrenergic blocker like phentolamine. In vitro incubation of testicular slices with nicotine failed to elicit any appreciable effect on delta 5-3 beta-hydroxysteroid dehydrogenase activity indicating lack of direct action of nicotine on testicular steroidogenesis.

In vitro studies on histochemical localization of testicular delta5-3beta-hydroxysteroid dehydrogenase activity from indomethacin pretreated rats--effect of prostaglandins and luteinizing hormone.

In vitro studies on the effect of LH and prostaglandins on delta5 3beta-hydroxysteroid dehydrogenase activity using indomethacin pre-treated testis as the experimental model, revealed a greater stimulation of the enzyme activity when the incubation medium contained LH and PGE2 both at a concentration of 1 microgram/ml in comparison to the effect produced by 1 microgram LH/ml alone, but the augmentory effect of PGE2 on testicular response to LH was not evidenced as the LH: PGE2 ratio became 1 : 10. Neither PGE2 nor PGF2A produced any stimulation of the enzyme activity at concentrations of 1, 10, or 20 microgram/ml in the incubating medium. PGF2A at concentrations of 1 or 10 microgram/ml did not appear to interfere with LH action on this steroidogenic enzyme. On the contrary, prostaglandins, both PGE2 and PGF2A, at concentrations of 20 microgram/ml, antagonized LH action over testicular delta5-3beta-hydroxysteroid dehydrogenase activity. On the basis of these findings, it appears that prostaglandin E2 in some way, is necessary for manifestation of the steroidogenic action of LH in testis.