Rat Vas Deferens Research Articles

Evidence for spare alpha 1-adrenoceptors for the accumulation of inositol phosphates in smooth muscle.

The accumulation of inositol phosphates (IP) in smooth muscle from rat vas deferens and caudal artery was maximally increased 3- to 4-fold in response to exposure of the tissues to 100 microM noradrenaline. Clonidine (up to 3 mM) was a partial agonist. Pretreatment of the tissues with the irreversible alpha-adrenoceptor antagonist phenoxybenzamine (0.3-10 microM) shifted the noradrenaline concentration-response curve to the right before depressing the maximum. The maximum of the clonidine concentration-response curve was depressed without significant change in the EC50 by the same treatment. These data, which are most easily interpreted as demonstrating the presence of a receptor reserve for IP accumulation, are discussed.

Characterization of the alpha 1-adrenoceptors of the rat prostate gland.

The alpha 1-adrenoceptor-mediated responses of the rat prostate to phenylephrine have been examined in-vitro. Phenylephrine induced concentration-dependent contractions of the isolated prostate gland which were antagonized by WB4101 (1-30 nM). Schild plot analysis of the antagonism yielded a straight line with a slope not significantly different from unity. The pKB value of 9.2 was similar to that obtained for WB4101 on the rat vas deferens (9.4) but was greater than that obtained on the rat spleen (8.4). Chloroethylclonidine depressed responses to phenylephrine of the rat spleen but not the prostate or the vas deferens. These results indicate that the rat prostate gland possesses a typical alpha 1A-adrenoceptor similar to that found in the vas deferens.

Presynaptic inhibition of neurotransmission in rat vas deferens by 2-(p-methoxyphenyl) adenosine, ethyl adenosine-5'-carboxylate and N-cyclopropyl adenosine-5'-carboxamide.

Presynaptic inhibition of neurotransmission in rat vas deferens by 2-(p-methoxyphenyl) adenosine, ethyl adenosine-5'-carboxylate and N-cyclopropyl adenosine-5'-carboxamide.

Ketanserin potentiates the prejunctional inhibitory effect of 5-hydroxytryptamine on rat vas deferens.

5-Hydroxytryptamine (5-HT) slightly inhibited the twitch contractions of rat vas deferens caused by single pulse field stimulation at 0.1 Hz. The inhibitory effect of 5-HT was much less in the epididymal portion than in the prostatic portion of the vas deferens. Ketanserin potentiated the prejunctional inhibitory effect of 5-HT and attenuated its stimulatory effect. This potentiation was observable only in the epididymal portion, of the vas deferens. Cyproheptadine and mianserin, but not methysergide, had essentially similar potentiating effects to those of ketanserin. These results suggest that the 5-HT receptor that mediates prejunctional inhibition is not of the 5-HT2 type, and that ketanserin acts by suppressing the 5-HT-induced stimulatory effect, which is possibly mediated by a postjunctional 5-HT2 receptor, thus unmasking the inhibitory effect of 5-HT.

Ha-117 and Ha-118 are potent dopamine receptor agonists.

In-vitro studies evaluated the presynaptic dopamine receptor activities of trans-N-propyl-7,9-dihydroxyoctahydrobenzo[f]quinoline (Ha-117) and trans-N-ethyl-7,9-dihydroxyoctahydrobenzo[f]quinoline (Ha-118) using isolated field-stimulated cat right atria. Ha-117 and Ha-118 were found to be potent dopamine receptor agonists since their effects were antagonized by haloperidol. Compounds were inactive on presynaptic alpha 2-adrenoceptors using rat vas deferens and guinea-pig ileum. Results show that both resorcinol derivatives of octahydrobenzo[f]quinoline are potent dopamine receptor agonists without having presynaptic alpha 2-adrenoceptor stimulating activity.

Evidence for alpha 2-adrenoceptor agonist activity of minoxidil.

The present investigation was undertaken to study the mechanism of action of minoxidil using various smooth muscle preparations. Minoxidil (4.7 x 10(-6) M to 4.7 x 10(-4) M) produced a concentration-dependent inhibition of field stimulation-evoked responses in rat anococcygeus muscle and vas deferens. The inhibition produced by minoxidil was antagonized by yohimbine (2.5 x 10(-7) M). Minoxidil (1.4 x 10(-5) M to 4.7 x 10(-4) M) also produced a concentration-dependent relaxation in oestrogen-primed potassium chloride-depolarized rat uterus. These responses were blocked not only by yohimbine but also by glibenclamide (2.02 x 10(-8) M). Our results suggest that minoxidil possesses alpha 2-adrenoceptor agonist activity in addition to potassium-channel-opening activity.

Stereoselectivity of catecholamines: differential effects of cocaine and desipramine on catecholamine-induced contractions of the rat isolated vas deferens.

The effect of uptake inhibitors, cocaine and desipramine, on the contractile response of the rat isolated vas deferens to the enantiomers of noradrenaline and adrenaline and to the corresponding deoxy-derivatives, dopamine and epinephline, was investigated. Cocaine (10(-6)M) significantly potentiated all six agonists; the effect was most marked for the laevo-isomers (-)-noradrenaline and (-)-adrenaline. Desipramine (10(-7) M) also potentiated (-)-noradrenaline, (+)-noradrenaline, (-)-adrenaline, (+)-adrenaline and epinephline but, in contrast, antagonized dopamine. This selective antagonism of dopamine by desipramine was also observed for the separated epididymal and prostatic ends of the rat vas deferens.

Differential blockade of pre- and postsynaptic alpha-adrenoceptors by the 2-R and 2-S enantiomers of WB4101.

Agonists and antagonists of the alpha-adrenoceptor have been shown to possess different degrees of potency at the pre- and postsynaptic levels. The present investigation was undertaken to see whether the two optical isomers of WB4101 likewise exhibit differential blockade at the two receptor sites. This was achieved by measuring the potencies of 2-R and 2-S WB4101 against noradrenaline-induced contractions of the rat isolated vas deferens and against clonidine-induced inhibition of the twitch response in field stimulated rat vas deferens. Results showed that though the enantiomers exhibited widely differing potency, as indicated by calculations of pA2 values, at the postsynaptic level, they possessed almost identical potency presynaptically. In addition, 2-aminomethyl-1,4-benzodioxan itself both exhibited reasonable presynaptic alpha-adrenoceptor blocking activity, whilst being devoid of activity postsynaptically. The values for slope on the Schild plots for 2-R and 2-S WB4101 indicated that they produced classical competitive antagonism at the postsynaptic receptor but at the presynaptic level the values for slope were indicative of a non-competitive type of blockade. Results are discussed in terms of recent suggestions of that agonists and antagonists of the alpha-adrenoceptor may not share a common mechanism or site of action at the presynaptic level.

A thin-layer chromatographic procedure for the assay of labelled noradrenaline and its metabolites in tissues and in incubation medium.

A method for the extraction, separation and quantitative determination of [3H]noradrenaline [3H-NA] and its five major metabolites has been devised using thin layer chromatography. This procedure was used to study the pattern of 3H-NA and its metabolites in the total radioactivity of the tissues and that released spontaneously from the rat isolated vas deferens. Whereas in tissues 3H-NA represented almost all of the total radioactivity (94-8+/-0.47%), in the samples of spontaneous outflow it represented only 16-8+/-2.1%. The rest was mostly accounted for by the five metabolites, primarily 3H-DOPEG and 3H-MOPEG. These findings show that in the rat vas deferens 3H-NA is preferentially metabolized via the two glycol derivatives, i.e. 3H-DOPEG and 3H-MOPEG.

Lack of Mixed Agonist-Antagonist Properties of [Gln8-Gly31]-βh-EP-Gly-Gly-NH2 and [Arg9,19,24,28,29]-βh-EP in the Rat Vas Deferens Neuroeffector Junction: Studies with Naloxone, β-Funaltrexamine and ICI 174,864

The 1-27 truncated fragment of beta h-endorphin (beta h-EP) as well as [Gln8,Gly31]-beta h-EP-Gly-Gly-NH2 or [Arg9,19,24,28,29]-beta h-EP exhibited opiate agonist activity in the rat vas deferens bioassay; the potency of these peptides was 3 to 6 times less than that of beta h-EP. None of these compounds exhibited any degree of antagonism towards the inhibitory action of beta h-EP. Naloxone antagonized and reversed the inhibitory action of beta h-EP and its analogues though with varying potencies. The apparent naloxone-pA2 value for beta h-EP was 8.94; that for [Gln8-Gly31]-beta h-EP-Gly-Gly-NH2 was 8.08 and that for [Arg9,19,24,28,29]-beta h-EP was 8.38. beta-Funaltrexamine (beta-FNA) potently antagonized the inhibitory action of beta h-EP following non-equilibrium kinetics. Tissue preincubation with 10 nM beta-FNA for 60 min followed by extensive washing caused a 10-fold increase in the beta h-EP IC50. However, 10 nM beta-FNA caused only a 1.2 increase in the IC50 of [Gln8,Gly31]-beta h-EP-Gly-Gly-NH2 and a 4.1-fold increase in the IC50 of [Arg9,19,24,28,29]-beta h-EP. In contrast, preincubation of the tissue with 3 microM ICI 174,864 did not modify the potency of beta h-EP or its structural analogues. However, a 60 min pretreatment with 10 microM beta-FNA followed by the addition of 3 microM ICI 174,864 revealed a further decrease in the potency of the opiopeptins compared with tissues exposed to beta-FNA alone or ICI 174,864 alone. In conclusion, the inhibitory action of these peptides is remarkably sensitive to beta-FNA antagonism; in addition the peptides act as pure opiate agonists in marked contrast with the agonist-antagonist properties described in the CNS.

Contraction of rat vas deferens by cocaine.

Contraction of rat vas deferens by cocaine.

N-Chloroacetyl 5-methoxytryptamine (isamide): a selective antagonist of 5-hydroxytryptamine in the rat uterus.

Isamide, the N-chloroacetyl derivative of 5-methoxytryptamine, produced a dose-dependent competitive blockade of uterine contractions in vitro induced by 5-HT. The pA2 value for the 5-HT-isamide interaction was 4.42. The blockade was short-lasting and reversible; after recovery, a dose-dependent increase in the uterine sensitivity to 5-HT was found. The blockade proved to be selective to the 5-HT receptor. The simultaneous application of 5-HT plus isamide partially prevented the 5-HT-induced auto blockade phenomenon. In addition, isamide did not affect the contractile responses of the uterus to oxytocin or bradykinin or the contractile effects of the rat vas deferens to adrenaline.

Pre-junctional alpha 2-adrenoceptor activity of B-HT920.

An in-vitro study has been carried out on the pre-junctional alpha 2-adrenoceptor activity of the thiazoloazepine derivative B-HT 920 (6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo[4,5-d]-azepine) using field-stimulated rat vas deferens and guinea-pig ileum. The alpha 2-selective agonists clonidine (an imidazoline derivative) and alpha-methyl noradrenaline (a beta-phenethylamine derivative) were compared. Results show that B-HT 920 is a potent agonist on pre-junctional alpha 2-adrenoceptors and is competitively antagonized by the selective alpha 2-adrenoceptor antagonist yohimbine. The characteristics of the pharmacological responses obtained with B-HT920 indicate that it interacts with the receptor in an imidazoline-like, rather than a beta-phenethylamine-like, manner.

Some pharmacological properties of the circular smooth muscle layer of the rat vas deferens.

Vas deferens preparations were perfused in-vitro through the lumen and externally with a modified Tyrode solution alone or containing drugs. Contractions of the circular (internal) smooth muscle layer were recorded as changes in the pressure of internal perfusion. Contractions of the longitudinal (external) layer were simultaneously recorded through a tension transducer. When the organ was perfused through the lumen, the circular layer contracted after addition of methacholine (pD2 = 4.13), and noradrenaline (pD2 = 5.00), and relaxed after addition of isoprenaline (pD2 = 5.22). These effects were also observed when the drugs were perfused externally, although with lower values of pD2 for noradrenaline and methacholine. The circular fibres were less sensitive when compared with the longitudinal fibres perfused externally with the above agonists. Methacholine-induced contractions of the circular layer were competitively antagonized by atropine (pA2 = 8.53), indicating the presence of muscarinic receptors. The effects induced by noradrenaline and isoprenaline were antagonized by indoramin (pA2 = 7.78), and timolol (pA2 = 8.68), respectively, indicating the presence of alpha- and beta-adrenoceptors. The effect of noradrenaline was potentiated by cocaine and denervation, indicating the presence of neuronal uptake, and by corticosterone, indicating the presence of extraneuronal uptake in the circular layer.

In vitro and in vivo alpha-blocking activity of thymoxamine and its two metabolites.

The alpha-adrenoceptor potency of thymoxamine and its two metabolites deacetylthymoxamine and demethyldeacetylthymoxamine were determined on the contraction of rat vas deferens induced by noradrenaline, the blood pressure increase induced by noradrenaline given i.v. to dogs and the contraction of the nictitating membrane induced by electrical stimulation in cats. In vivo the three drugs were administered at 6.35 x 10(-6) mol kg-1 intravenously. Deacetylthymoxamine presented nearly the same alpha-blocking activity as the parent drug. This was ascribed in vivo to the rapid deacetylation of thymoxamine. Demethyldeacetylthymoxamine was less active. In vitro its pA2 was 6.20 +/- 0.09 compared with 6.75 +/- 0.20 for thymoxamine and 6.57 +/- 0.13 for deacetylthymoxamine. In vivo, it was inactive in dog and less active than the other two drugs soon after its administration in the cat. The oral LD 50 values in the mouse for the three drugs were respectively 0.81, 0.71 and 1.14 mmol kg-1 for thymoxamine, deacetylthymoxamine and demethyldeacetylthymoxamine.

Effects of novel tacripyrines ITH12117 and ITH12118 on rat vas deferens contractions, calcium transients and cholinesterase activity

We have recently synthesized a new series of hybrid compounds having the moieties of tacrine, a potent inhibitor of brain and peripheral acetylcholinesterase (AChE), and nimodipine, a blocker of L-type voltage-dependent calcium channels (VDCCs). These compounds were designed to target AChE and L calcium channels in the brain, as potential therapeutic agents in Alzheimer's disease. We performed the present study to determine the main peripheral side effects of two of these compounds, ITH12117 and ITH12118. We have here shown that in rat vas deferens these compounds inhibited AChE with a potency about 1000-fold lower than that of physostigmine or tacrine. Furthermore, the hybrid compounds enhanced contractions evoked by acetylcholine, with a potency about 100-fold lower than that of physostigmine or tacrine. Additionally, contractions induced by Ca2+ on depolarized vas deferens were blocked by nimodipine with greater efficacy, compared with ITH12117 and ITH12118. Compound ITH12118 (1μM) caused a pronounced inhibition of the tonic (but not phasic) contraction elicited by electrical field stimulation. Furthermore, the same dose of nimodipine and ITH12118 blocked by 75% cytosolic Ca2+ elevations produced by acetylcholine, noradrenaline, or ATP. As a matter of comparison, we showed that rat brain cortex AChE was inhibited by ITH12118 with a potency 10 to 20-fold higher than that for vas deferens. This study shows that ITH12118 could be a paradigmatic multitarget compound having selective brain effects with smaller peripheral side effects. This may help to orient the search of new neuroprotective compounds with potential therapeutic application in Alzheimer's disease.

Regarding Article “Receptor Activity-Modifying Protein-1 Augments Cerebrovascular Responses to Calcitonin Gene-Related Peptide and Inhibits Angiotensin II-Induced Vascular Dysfunction”

HomeStrokeVol. 42, No. 2Regarding Article “Receptor Activity-Modifying Protein-1 Augments Cerebrovascular Responses to Calcitonin Gene-Related Peptide and Inhibits Angiotensin II-Induced Vascular Dysfunction” Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBRegarding Article “Receptor Activity-Modifying Protein-1 Augments Cerebrovascular Responses to Calcitonin Gene-Related Peptide and Inhibits Angiotensin II-Induced Vascular Dysfunction” Kazushi Tsuda, MD, FAHA Kazushi TsudaKazushi Tsuda Cardiovascular and Metabolic Research Center Kansai University of Health Sciences Osaka, Japan (Tsuda) Search for more papers by this author Originally published30 Dec 2010https://doi.org/10.1161/STROKEAHA.110.604272Stroke. 2011;42:e24Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: January 1, 2010: Previous Version 1 To the Editor:We read with great interest the recent article by Dr Chrissobolis and colleagues1 dealing with the cerebrovascular responses in the transgenic mice with overexpression of the receptor activity-modifying protein-1 (RAMP1) for calcitonin gene-related peptide (CGRP) receptors. The results of their study demonstrated that the responses to CGRP in carotid and basilar arteries in vitro as well as cerebral arterioles in vivo were selectively enhanced in human RAMP1 transgenic mice compared with controls. In addition, the authors presented that angiotensin II-induced oxidative stress and endothelial dysfunction was prevented after expression of RAMP1. The authors propose the hypothesis that RAMP1 may be an important mediator of vascular protection and a new therapeutic target in vascular disease.Several studies have reported that enhanced activity of the sympathetic nervous system might actively participate in the pathogenesis of vascular dysfunction. In a study we presented previously, the changes in norepinephrine release induced by CGRP was investigated in the rat central nervous system.2 In an in vitro study, we showed that CGRP inhibited the stimulation-evoked norepinephrine release in a dose-dependent manner. It was also demonstrated that a dihydropyridine-sensitive calcium channel agonist, Bay K 8644, significantly reversed the inhibitory effect of CGRP on norepinephrine release, indicating that CGRP might partially interact with dihydropyridine-sensitive calcium channels and modulate intracellular calcium mobilization. Furthermore, we showed that the inhibitory action on CGRP on norepinephrine release was significantly attenuated in spontaneously hypertensive rats compared with normotensive rats.3 In the peripheral tissues, Ohhashi and Jacobowitz4 observed that CGRP might have reduced the electric stimulation-induced contraction of rat vas deferens, suggesting that CGRP might inhibit norepinephrine release during adrenergic nerve stimulation. It can be speculated that the sympatholytic action of CGRP might be a defense against vascular dysfunction. Because angiotensin II may stimulate the sympathetic neurotransmission in the central nervous system,5 we would like to know whether changes in sympathetic nervous activity might be associated with the magnitude of the RAMP1 overexpression or whether CGRP might suppress the angiotensin II-induced sympathetic hyperactivity in the study of Dr Chrissobolis and colleagues. Further studies should be performed to assess more thoroughly the interactions between CGRP and the sympathetic nervous system and their role in the protective effect against the angiotensin II-induced vascular dysfunction in the RAMP1 transgenic mice.Kazushi Tsuda, MD, FAHA Cardiovascular and Metabolic Research Center Kansai University of Health Sciences Osaka, JapanDisclosuresNone.FootnotesStroke welcomes Letters to the Editor and will publish them, if suitable, as space permits. Letters must reference a Stroke published-ahead-of-print article or an article printed within the past 3 weeks. The maximum length is 750 words including no more than 5 references and 3 authors. Please submit letters typed double-spaced. Letters may be shortened or edited. Include a completed copyright transfer agreement form (available online at http://stroke.ahajournals.org and http://submit-stroke.ahajournals.org).

Nociceptin/orphanin FQ receptor knockout rats: In vitro and in vivo studies

Nociceptin/orphanin FQ (N/OFQ) regulates several biological functions via selective activation of the N/OFQ peptide (NOP) receptor. Recently knockout rats for the NOP receptor gene (NOP(−/−)) have been generated; these animals were used in the present study to investigate their emotional (open field, elevated plus maze, and forced swimming test), locomotor (drag and rotarod test), and nociceptive (plantar and formalin test) phenotypes in comparison with their NOP(+/+) littermates. In addition, N/OFQ sensitivity has been assessed in electrically stimulated vas deferens tissues taken from NOP(+/+) and NOP(−/−) rats. In the elevated plus maze and forced swimming tests NOP(−/−) rats showed anxiety- and anti-depressant-like phenotype, respectively. No differences were found in the open field test. NOP(−/−) rats outperformed their NOP(+/+) littermates in two motor behaviour assays. Genetic ablation of the NOP receptor gene produced a statistically significant increase in nociceptive behaviour of the mutant rats in the formalin test. Finally, in the electrically stimulated rat vas deferens taken from NOP(+/+) tissues, N/OFQ inhibited in a concentration-dependent manner the electrically induced twitches while the peptide was inactive in tissues taken from NOP(−/−) animals. These results, in line with previous findings obtained with selective NOP receptor antagonists in mice and rats and with mouse knockout studies, clearly indicate that endogenous N/OFQ–NOP receptor signalling plays an important role in controlling anxiety- and mood-related behaviours, exercise-driven locomotor activity and nociception. These observations are relevant for defining the therapeutic indications (and contraindications) of NOP receptor antagonists.

Endogenous hydrogen sulfide as a mediator of vas deferens smooth muscle relaxation

Cystathionine-lyase and cystathionine-synthase, both H(2)S-synthesizing enzymes, were functionally expressed in the vas deferens of rat, mice, and human. Endogenous H(2)S mediated vas deferens smooth muscle relaxation.

Rat vas deferens relaxation induced by Vitis vinifera leaf extract

The relaxatory effect of Vitis vinifera leaf extract on rat uterus has been reported and it was postulated that, the extract relaxed through the blockade of voltage dependent calcium channels. The extract also, relaxed rat aorta through NO and was dependent on the functional endothelium. In the present study, the effect of Vitis vinifera hydroalcoholic leaf extract (VHLE) on rat vas deferens precontracted by KCl and epinephrine was investigated. Extract was prepared by maceration method using 70% alcohol and then the solvent was evaporated. The isolated vas deferen of adult Sprague-Dawley rat was suspended in an organ bath containing Tyrod’s solution (30?C, pH 7.4) bubbled with air. Following 30 min period equilibrium, tissue was contracted by either epinephrine (EN, 2 µg/ml) or KCl (80 mM) under 1 g initial tension and tissue responses was recorded isometrically. VLHE was applied to the organ bath in a non-cumulative manner. Results are presented in mean±SEM of (g) contraction force or percentage of relaxation (%). VHLE (1, 2, 4 and 8 mg/ml) reduced KCl-induced contractions significantly (P