Contractility Of Rat Vas Deferens Research Articles

Effect of noni (Morinda citrifolia Linn.) fruit and its bioactive principles scopoletin and rutin on rat vas deferens contractility: an ex vivo study.

This study examined the effect of methanolic extract of Morinda citrifolia Linn. (MMC) and its bioactive principles, scopoletin and rutin, on dopamine- and noradrenaline-evoked contractility in isolated rat vas deferens preparations. MMC (1–40 mg/mL), scopoletin (1–200 μg/mL), and rutin hydrate (0.6–312.6 μg/mL) dose-dependently inhibited the contractility evoked by submaximal concentrations of both dopamine and noradrenaline, respectively. Haloperidol and prazosin, reference dopamine D2, and α 1-adrenoceptors antagonists significantly reversed the dopamine- and noradrenaline-induced contractions, respectively, in a dose-dependent manner. Interestingly, MMC per se at higher doses (60–100 mg/mL) showed dose-dependent contractile response in rat vas deferens which was partially inhibited by high doses of haloperidol but not by prazosin. These results demonstrated the biphasic effects of MMC on dopaminergic system; that is, antidopaminergic effect at lower concentrations (<40 mg/mL) and dopaminergic agonistic effect at higher concentrations (>60 mg/mL). However, similar contractile response at high doses of scopoletin (0.5–5 mg/mL) and rutin hydrate (0.5–5 mg/mL) per se was not observed. Therefore, it can be concluded that the bioactive principles of MMC, scopoletin, and rutin might be responsible for the antidopaminergic and antiadrenergic activities of MMC.

Purinergic contraction of the rat vas deferens in L-NAME-induced hypertension: effect of sildenafil

Hypertension (HTN) is a risk factor for erectile dysfunction, but its effect on vas deferens (VD) contractility and the ejaculatory response has not been delineated. NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, was used for induction of nitric oxide (NO)-deficient HTN. Our aim was to evaluate the effects of L-NAME-induced HTN on rat VD contractility and to determine whether sildenafil affects VD contractility. A total of 36 male rats were divided into (1) control, (2) L-NAME-HTN, (3) sildenafil treated L-NAME-HTN groups. Group 2 was treated with L-NAME (40 mg kg(-1) per day) in drinking water for 4 weeks. Group 3 received sildenafil (1.5 mg kg(-1) per day, by oral gavage) concomitantly with L-NAME. The prostatic portion of the VD was subjected to electrical field stimulation (EFS, 1-20 Hz), and the P2X(1) agonist alpha,beta-methylene ATP (alpha,beta-meATP, 100 micromol L(-1)-1 micromol L(-1)) and the alpha1-adrenoceptor agonist phenylephrine (Phe, 100 micromol L(-1)-1 mmol L(-1)) were used to construct concentration-response curves. These experiments were repeated in the presence of P2X receptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS, 30 micromol L(-1)). VD contractions in response to EFS, alpha,beta-meATP and Phe were significantly enhanced by L-NAME. Sildenafil treatment in the L-NAME group improved the contractile response of VD to EFS (20 Hz). In the presence of PPADS, the enhanced contractile response of VD to EFS and alpha,beta-meATP in hypertensive rats was reversed. In the rat model of chronic NO depletion, the purinergic and adrenergic components and EFS affect VD contractility. The VD contractile response may be mediated more by the purinergic system than the adrenergic system, and sildenafil may alter the ejaculatory response in men with PE.

Specific H +/K +-ATPase inhibitors decreased contractile responses of isolated rat vas deferens

The effect of H +/K +-ATPase inhibitors on rat vas deferens contractility was investigated in vitro. Omeprazole (100–300 μM), lansoprazole (100–300 μM) and SCH 28080 (10–100 μM) (2-methyl-8-(phenylmethoxy)-imidazo[1,2-a]pyridine-3-acetonitrile) decreased contractile responses of vas deferens to electrical field stimulation, high K + (80 mM) and phenylephrine in a reversible, reproducible and concentration-dependent manner. The inhibitory potency of lansoprazole on vas deferens contractility was increased in relatively acidic solution (pH 6.9), suggesting that the site of action may be related to H +/K +-ATPase. However, lansoprazole-induced inhibition on contractility was unaltered in K + free solution, indicating that the mechanism of action is independent from H +/K +-ATPase. Reversible nature of omeprazole and lansoprazole-induced inhibition on contractility also suggests that the effects are not due to inhibition of H +/K +-ATPase, since both compounds are irreversible inhibitors of the enzyme. Presence of ouabain (5 μM) did not decrease lansoprazole-induced inhibition on contractility but potentiated the inhibitory effect of lansoprazole, suggesting that lansoprazole-induced inhibition is not mediated by the inhibition of Na +/K +-ATPase. Calcium-induced contractions in high K +–Ca 2+ free medium were completely antagonized by lansoprazole, implying that lansoprazole inhibits Ca 2+ entry through voltage-gated channels. In conclusion, three H +/K +-ATPase inhibitors decreased contractile responses of rat vas deferens to various stimulants in vitro. They may act on a common mechanism, which plays a crucial role in regulating rat vas deferens contractility and this mechanism is probably involved in the regulation of intracellular Ca 2+.

2-(4'-aminobenzenamine)-pyrimidine, a new alpha-antagonist from Autonoë madeirensis.

A new natural pyrimidine derivative, 2-(4'-aminobenzenamine)-pyrimidine (1), was isolated from the bulbs of Autonoë madeirensis, a Hyacinthaceae of the Madeira Archipelago (Portugal) and the structure determined on the basis of spectroscopic data. As some pyrimidine compounds are important alpha1-adrenergic antagonists, we investigated the effect of 1 on rat vas deferens contractility induced by the alpha1-agonist phenylephrine. In concentrations virtually devoid of effect on the rat vas deferens contractility, 1 shifted to the right the concentration-response curves of phenylephrine without changing the maximal effect. These results provide evidence that 1 acts as an alpha1-adrenoceptor antagonist and suggest a competitive mechanism of action.

Long-term use of sertraline leads to alterations in contractility of rat isolated vas deferens.

Previous experiments with rat isolated vas deferens have shown that sertraline pretreatment inhibits contractile responses to noradrenaline, KCl, serotonin and electrical field stimulation. In the present study, the aim was to investigate the effects of long-term use of sertraline on contractile responses of rat isolated vas deferens. Fifteen Sprague-Dawley rats were given long-term (21 days) sertraline treatment, while another 15 were used as control. Both vas deferens were excised. Epididymal and prostatic segments of each underwent electrical field and chemical stimulation (noradrenaline, serotonin, acetylcholine, adenosine-triphosphate). Epididymal and prostatic segments had different contraction characteristics. Long-term sertraline treatment inhibited contractile responses of vas deferens segments to electrical field stimulation. The responses to noradrenaline were amplified with a left shift on both segments. Responses to serotonin had only a left shift on epididymal segments, while no contractile responses were observed on prostatic segments of the groups. Long-term treatment with sertraline had peripheral effects on rat vas deferens contractility, and some of the effects may be through mechanisms other than the inhibition of serotonin re-uptake.

Nitric oxide synthase/guanylate cyclase pathway modulates the rat vas deferens contractility induced by phenylephrine.

The involvement of the nitric oxide synthase/soluble guanylate cyclase pathway on the modulation of phenylephrine-induced contractility in the rat vas deferens was investigated. Phenlylephrine-concentration response curves were obtained in absence and in presence of inhibitors, N(G)-Nitro-L-arginine (L-NOARG), NG-Nitro-L-arginine methyl esther (L-NAME) or N(G)-monomethyl-L-arginine (L-NMMA) or GC inhibitior, 1H-(1,2,4)-oxadiaziol-(4,3-a)quinoxalin-1-one (ODQ) or nitric oxide donor, 3-morpholinosydnonimine hydrochloride (SIN-1) alone or together with L-NMMA or ODQ. Both nitric oxide synthase and GC inhibitors reduced the Phe-Emax. SIN-1 alone did not change phenylephrine-induced responses and it could reverse the L-NMMA effect but not ODQ effect. The reduction of the phenylephrine-induced contractility obtained in consequence of the inhibition of the nitric oxide/GC pathway suggest that, in the rat vas deferens, despite its well identified relaxant properties, nitric oxide potentiates the contractility induced by adrenergic stimulation.

Failure of AH11110A to functionally discriminate between α 1-adrenoceptor subtypes A, B and D or between α 1- and α 2-adrenoceptors

The potency of the putatively α 1B-adrenoceptor selective drug, 1-[biphenyl-2-yloxy]-4-imino-4-piperidin-1-yl-butan-2-ol (AH11110A), to antagonize contraction upon stimulation of α 1A-adrenoceptors in rat vas deferens and rat perfused kidney, α 1B-adrenoceptors in guinea-pig spleen, mouse spleen and rabbit aorta, and α 1D-adrenoceptors in rat aorta and pulmonary artery was evaluated and compared to that of a number of subtype-discriminating antagonists. N-[3-[4-(2-Methoxyphenyl)-1-piperazinyl]propyl]-3-methyl-4-oxo-2-phenyl-4 H-1-benzopyran-8-carboxamide (Rec 15/2739) and (±)-1,3,5-trimethyl-6-[[3-[4-((2,3-dihydro-2-hydroxymethyl)-1,4-benzodioxin-5-yl)-1-piperazinyl]propyl]amino]-2,4(1 H,3 H)-pyrimidinedione (B8805-033) were confirmed as selective for α 1A-adrenoceptors, 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione (BMY 7378), 8-[2-(1,4-benzodioxan-2-ylmethylamino)ethyl]-8-azaspiro[4.5]decane-7,9-dione (MDL 73005EF), and cystazosin were found to be selective for α 1D-adrenoceptors, whereas spiperone was weakly selective for α 1B-over α 1A-adrenoceptors. However, from the functional affinity profile obtained for AH11110A at α 1A-adrenoceptors (p A 2=6.41 in rat vas deferens), α 1B-adrenoceptors (p A 2=5.40–6.54) and α 1D-adrenoceptors (p A 2=5.47–5.48), the affinity and presumed selectivity previously obtained for AH11110A in radioligand binding studies at native α 1B- and cloned α 1b-adrenoceptors (p K i=7.10–7.73) could not be confirmed. Additionally, AH11110A enhanced the general contractility of rat vas deferens, produced a bell-shaped dose–response curve of vasodilation in perfused rat kidney, and its antagonism in most other tissues was not simply competitive. The affinity of AH11110A for prejunctional α 2-adrenoceptors in rabbit vas deferens (p A 2=5.44) was not much lower than that displayed for α 1-adrenoceptor subtypes, revealing that AH11110A, besides α 1-adrenoceptors, also interacts with α 2-adrenoceptors, and thus may be unsuitable for α-adrenoceptor subtype characterization, at least in smooth muscle containing functional studies.

Modulatory Effect of Protein Kinase C Activator on Contractility of Rat Vas deferens

The modulatory effect of the protein kinase C activator was examined on contraction of rat isolated vas deferens induced by constrictive agonists, noradrenaline (NA), ATP, BaCl₂ and high K⁺. Phorbol 12,13-diacetate (PDA, 1 µmol/l) induced a transient extracellular Ca²⁺-dependent contraction while the inactive analogue, 4α-phorbol (1 µmol/l) had no effect. PDA significantly enhanced the peak amplitude of the contractile response to NA (0.1–10 µmol/l), ATP (100 µmol/l), Ba²⁺ (3 mmol/l) or high K⁺ (30 mmol/l). Staurosporine at 30 nmol/l reduced the enhancing effect of PDA on the agonist-induced contraction. NA (10 µmol/l) produced a phasic contraction followed by a sustained contraction, while ATP induced monophasic contraction. Pretreatment with nifedipine (10 nmol/l) had no effect on the phasic contraction induced by NA, but it significantly reduced ATP- or high K⁺-induced contraction. Staurosporine (30 nmol/l) alone attenuated the peak contractile response induced by NA or ATP but not by Ba²⁺. NA produced a transient contraction in Ca²⁺-free Krebs solution, and PDA (1 µmol/l) markedly enhanced this effect. These novel data indicate that activation of a protein kinase C-dependent mechanism not only affects contraction mediated by Ca²⁺ influx through voltage-sensitive Ca²⁺ channels, but also promotes intracellular Ca²⁺ release or intracellular Ca²⁺-mediated contractile mechanism in rat vas deferens.

Long-term treatment with fluoxetine associates with peripheral effects on rat vas deferens contractility

The aim of this work was to study whether long-term treatment with fluoxetine could induce peripheral effects by modifying vas deferens contractile activity. For this purpose the contractile response to NE, and 5-HT of vas deferens isolated from male Wistar rats that received fluoxetine 10 mg/kg/day ip, during 21 days, was studied using the isolated organ bath technique. Results show that vas deferens of treated rats presented spontaneous activity, an effect that was abolished by prazosin and isoproterenol and that was not affected by nitroprusside or indomethacin. In addition, fluoxetine did not modify the response to calcium suggesting that spontaneous activity was not a consequence of an abnormal calcium movement. Fluoxetine induced a significant increase in the response of vas deferens to 5-HT and to low NE concentrations while NE maximal effect was unaffected. Fluoxetine treatment did not modify the binding parameters of [ 3H]-prazosin to vas deferens. It is concluded that long-term treatment with fluoxetine modifies vas deferens contractile activity. This effect could be the result of an alteration of adrenergic neurotransmission and could account for some of the untoward effects observed during clinical course with fluoxetine.

Effects of octreotide on the contractility of isolated rat vas deferens

This study was performed to investigate the effect of octreotide on the contractility of rat vas deferens. The smooth muscle strips isolated from the prostatic portion were myographied in isolated organ bath, Electric field stimulation (monophasic square wave, duration: 1 mSec, voltage : 50 V, frequency : 5 Hz or 30 Hz, train: 10 Sec) produced reproducible contraction. The contraction was composed of two component, first phasic component (FPC) and second tonic component (STC). These contractions were abolished by tetrodotoxin (). Octreotide inhibited the field stimulation induced contractions both FPC and STC concentration-dependently. The FPC was decreased by a desentization of purinergic receptor by pretreatment of mATP, and the STC was decreased by pretreatment of reserpine(3 mg/kg, IP) 24 hours before experiments. Octreotide reduced the field stimulation induced contraction in the presence of mATP and of reserpinized muscle strips. The inhibitory effect of octreotide was more potent at 5 Hz than at 30 Hz. Octreotide did not affect basal ton and exogenous norepinephrine- or ATP-induced contraction. These results suggest that octreotide inhibit the contractility of the isolated rat vas deferens by inhibition of the release of neurotransmitters, both ATP and norepinephrine from adrenergic nerve terminal.

The mechanism of supersensitivity to norepinephrine induced by cocaine in rat isolated vas deferens

The influence of cocaine on the response of rat vas deferens to norepinephrine, angiotensin, acetylcholine, K + and Ba ++ was examined. Cocaine produced a significant elevation of maximum response to norepinephrine as well as left-ward shift of the dose-response curve. The effect of cocaine on the dose-response curves for angiotensin, acetylcholine and K + was mainly reflected in the enhancement of maximum responses. The contractility of rat vas deferens was extremely dependent upon calcium concentration in the medium, and cocaine lowered the threshold concentration of calcium required for contraction. The findings lead to the conclusion that cocaine potentiates the effect of norepinephrine in at least two different ways: (1) a presynaptic inhibition of norepinephrine uptake, and (2) a postsynaptic direct action which is nonspecific.