Bisected Vas Deferens Research Articles

α1- and α2-Adrenoceptor hyporesponsiveness in isolated bisected vas deferens of bile duct-ligated rats

It has been suggested that cholestasis accompanied with changes in autonomic balance and hyporesponsiveness in muscarinic and adrenergic receptors of some organs, e.g. cardiovascular system. Increased plasma levels of epinephrine and norepinephrine has been shown during cholestasis suggesting augmented activity of sympathetic nervous system. In this study we evaluate both alpha(1) and alpha(2) responsiveness in isolated rat vas deferens, as a tissue with rich adrenergic innervations. Epididymal and prostatic halves of vas deferens responsiveness have been studied to phenylephrine and clonidine respectively in three groups of un-operated, sham-operated (sham), and bile duct-ligated (BDL) rats. Our results indicate that in vas deferens of BDL animals, the concentration-response curve of both phenylephrine and clonidine shifted to rightward compared to control group, while the position of concentration-response curve of sham group did not change significantly (P > 0.05). EC(50) of phenylephrine and IC(50) of clonidine were increased showing a decreased responsiveness of tissue to phenylephrine (P < 0.05) and clonidine (P < 0.001) in BDL rats. In this study, both subtype of alpha-adrenoceptors (alpha(1) and alpha(2)) has been studied in cholestatic rat vas deference. Our results showed that cholestasis induce hyporesponsiveness to phenylephrine and clonidine. These results are consistent with previous reports, suggesting the hyporesponsiveness of alpha(1)-adrenoceptors in pulmonary artery and papillary muscle and mesenteric beds. Our conclusion is that the cholestasis induces hyporesponsiveness to phenylephrine and clonidine in epididymal (alpha(1)-adrenoceptors) and prostatic (alpha(2)-adrenoceptors) halves of rat vas deferens respectively. Although the logical explanation to this hyporesponsiveness is the down regulation but it has been suggested that it is not because of down regulation.

Selective impairment of noradrenergic transmission in the bisected rat vas deferens following photochemically‐induced cerebral ischaemia

Cerebrovascular disease may impair the autonomic control of peripheral organs including the male urogenital tract. This study investigates the effect of cortico-parietal focal ischaemia on the adrenergic and purinergic transmission in isolated epididymal and prostatic portion of rat vas deferens. Focal brain ischaemia was induced in male rats by photochemical activation following rose bengal intravenous injection. Twenty-four hours following brain ischaemia, cumulative and non-cumulative concentration-response curves were obtained for noradrenaline and alpha,beta-methylene ATP in the right and left epididymal and prostatic portions of the vas deferens. Both portions were also stimulated by single-pulse or pulse trains at 2-30 Hz to produce isometric contractions. In both portions from ischaemic rats the response to exogenous noradrenaline was markedly depressed compared with controls. Acute cortico-parietal ischaemia almost completely abolished the adrenergic phase of the response to single-pulse stimulation in the epididymal portion of the vas deferens. In addition, brain ischaemia deeply depressed phasic and tonic contractions of the frequency-response curve in both portions of bisected vas deferens. Cortico-parietal ischaemia produces a selective noradrenergic impairment at the level of male sexual secondary organs that may contribute to sexual dysfunction after stroke.

REGIONAL DIFFERENCES IN EXTRACELLULAR PURINE DEGRADATION IN THE PROSTATIC AND EPIDIDYMAL PORTIONS OF THE RAT VAS DEFERENS

1. The aim of the present study was to compare ecto-nucleotidase activities in rat bisected vas deferens using 1,N6-etheno(epsilon)-nucleotides (epsilon-ATP and epsilon-AMP) as substrates. Degradation was estimated by measuring the disappearance of the substrate and the appearance of its metabolites using HPLC with fluorescence detection. Incubation of tissue preparations (prostatic or epididymal portions) with 300 nmol/L epsilon-ATP at 37 degrees C caused a partial disappearance of epsilon-ATP and appearance of its metabolites (epsilon-ADP, epsilon-AMP and epsilon-adenosine). Incubation at 25 degrees C reduced epsilon-ATP degradation more in the prostatic than in the epididymal portion. 2. Incubation of tissue preparations with epsilon-AMP at 37 degrees C resulted in the disappearance of epsilon-AMP and the appearance of epsilon-adenosine, which was more pronounced in the epididymal than in the prostatic portion. Incubation at 25 degrees C reduced epsilon-AMP degradation more in the epididymal than in the prostatic portion. 3. Decreasing pH from 7.4 to 6.5 enhanced epsilon-AMP degradation only in the prostatic portion, whereas increasing pH from 7.4 to 8.5 enhanced epsilon-AMP degradation in both portions, but more markedly in the epididymal portion. The alkaline phosphatase inhibitors levamisole (10 mmol/L) and beta-glycerophosphate (10 mmol/L) reduced epsilon-AMP degradation only in the epididymal portion. 4. In conclusion, the results of the present study are compatible with the presence, in the bisected rat vas deferens, of an ecto-nucleotidase system that is involved in the degradation of extracellular purines, which may differ between the epididymal and prostatic portions, with the epididymal portion presenting a different and higher capacity to form adenosine.

Effect of in vivo and in vitro ethanol on adrenergic and purinergic responses of the bisected rat vas deferens to low and high frequency pulses.

1. This study investigates the effect of acute in vivo and in vitro ethanol administration on the contractions evoked electrically and by exogenous noradrenaline and alpha,beta-methylene-ATP in the rat bisected vas deferens. 2. In vivo ethanol treatment (3 g kg(-1), i.p.) significantly potentiated the early purinergic (phase I) and the delayed adrenergic (phase II) phases evoked by single-pulse stimulation of the epididymal portion of the rat vas deferens, leaving unaffected both phases in the prostatic portion. In vitro 50 mM ethanol significantly depressed phase I leaving unaffected phase II in both portions from untreated rats. In vitro ethanol significantly depressed phase I in the epididymal portion from in vivo ethanol treated animals and potentiated phase II in both portions. 3. In vivo ethanol treatment (3.0 g kg(-1), i.p.) selectively impaired the response to noradrenaline only in the prostatic portion of rat vas deferens while it was devoid of any action on alpha,beta-methylene-ATP contractions. Ethanol 50 mM in vitro was devoid of any action on the response to exogenous noradrenaline and alpha,beta-methylene-ATP in both tissues. 4. In vivo ethanol treatment slightly but significantly increased the phasic response in the epididymal portion to trains of stimuli (2-30 Hz). In vitro 50 mM ethanol was ineffective against the phasic and tonic contractions elicited by the tetanus in both portions. 5. It is concluded that ethanol treatment affects purinergic and adrenergic pathways of transmission possibly leading to a disruption of physiological contractions necessary to seminal emission.

Alcohol differentially affects noradrenergic and purinergic responses in the bisected rat vas deferens

This study investigates the effect of acute in vivo or in vitro ethanol administration on the adrenergic and purinergic responses in the epididymal and prostatic portion of rat vas deferens. Acute in vivo ethanol treatment (3.0 g/kg, i.p.) selectively impaired the response to noradrenaline in the prostatic portion of rat vas deferens, leaving unaffected the epididymal portion. In addition, the response evoked by the maximal concentration of α,β-methylene-ATP was significantly depressed by acute in vivo ethanol treatment in both the epididymal and prostatic segments. Ethanol 50 mM in vitro was devoid of any action on the response to exogenous noradrenaline in both tissues. Ethanol in vitro left unaltered the response to α,β-methylene-ATP in the epididymal portion, while potentiated the contractile response in the prostatic one. These results provide, for the first time, evidence that ethanol in vitro and in vivo differentially affects the noradrenergic and purinergic responses in the bisected vas deferens, suggesting that this substance may alter the male reproductive tract function.

Adrenergic and purinergic components in bisected vas deferens from spontaneously hypertensive rats.

1. Purinergic and adrenergic components of the contractile response to electrical field stimulation (EFS) have been investigated in epididymal and prostatic portions of Wystar Kyoto (WKY) and spontaneously hypertensive rat (SHR) vas deferens. 2. In both halves of SHR and WKY vas deferens, EFS (40 V, 0.5 ms for 30 s, 0.5-32 Hz) evoked frequency-related contractions. The neurogenic responses were biphasic, consisting of a rapid non-adrenergic response, dominant in the prostatic portion, followed by a slow tonic adrenergic component, dominant in the epididymal half. 3. Phasic and tonic components of the frequency-response curves evoked by EFS were significantly higher in the epididymal but not in the prostatic portion of vas deferens from SHR compared to WKY rats. 4. The alpha1-adrenoceptor antagonist prazosin (0.1 microM) was more effective against both components of the contractile response in the epididymal end of SHR than in WKY rats. 5. Inhibition by alpha, beta-methylene adenosine 5'-triphosphate (alpha,beta-meATP 3 and 30 microM) was higher in both components of the contractile responses in WKY preparations than in SHR. 6. Combined alpha1-adrenoceptor and P2x-purinoceptor antagonism virtually abolished the EFS-evoked contractile response in both strains. The degree of inhibition by prazosin (0.1 microM) after P2x-purinoceptor blockade was higher in SHR than in WKY rats. 7. These results demonstrate a modification in the purinergic and noradrenergic contribution to neurogenic responses in SHR and WKY animals besides a co-participation of ATP and noradrenaline in both contractile components of the response to EFS.

A1 adenosine receptor modulation of electrically-evoked contractions in the bisected vas deferens and cauda epididymis of the guinea-pig.

1. The effects of adenosine receptor agonists upon both electrically-evoked and phenylephrine-induced contractile responses were investigated in the bisected vas deferens and the cauda epididymis of the guinea-pig. Electrical field-stimulation (10 s trains of pulses at 9 Hz, 0.1 ms duration, supramaximal voltage) elicited biphasic and monophasic contractile responses from preparations of bisected vas deferens and cauda epididymis, respectively; these responses were abolished by tetrodotoxin (300 nM). 2. In the prostatic half of the vas deferens the A1 selective adenosine receptor agonists, N6-cyclopentyladenosine (CPA) and (2S)-N6-[2-endo-norbornyl]adenosine ((S)-ENBA) and the non-selective A1/A2 adenosine receptor agonist, 5'-N-ethylcarboxamidoadenosine (NECA) inhibited electrically-evoked contractions (pIC50+/-s.e.mean values 6.15+/-0.24, 5.99+/-0.26 and 5.51+/-0.24, respectively). The responses to CPA were blocked by the A1 adenosine receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine, DPCPX (100 nM). 3. In the epididymal half of the vas deferens NECA potentiated (at < or = 100 nM) and inhibited (at > or = 1 microM) electrically-evoked contractions. In the presence of the non-selective alpha-adrenoceptor antagonist phentolamine (3 microM), the alpha1-adrenoceptor antagonist, prazosin (100 nM), or at a reduced train length (3 s) NECA inhibited electrically-evoked contractions (pIC50 values 6.05+/-0.25, 5.97+/-0.29 and 5.71 +/-0.27, respectively). CPA (at 10 microM) also inhibited electrically-evoked contractions in this half of the vas deferens. In the presence of prazosin (100 nM), CPA also inhibited electrically-evoked contractions (pIC50 6.14+/-0.67); this effect was antagonized by DPCPX (30 nM, apparent pK(B) 8.26+/-0.88). In the presence of the P2 purinoceptor antagonist, suramin (300 microM), CPA (up to 1 microM) potentiated electrically-evoked contractions. 4. NECA, CPA and APNEA potentiated electrically-evoked contractions in preparations of cauda epididymis (pEC50 values 7.49+/-0.62, 7.65+/-0.74 and 5.84+/-0.86, respectively), the response to CPA was competitively antagonized by DPCPX (100 nM) with an apparent pK(B) value of 7.64+/-0.64. 5. The alpha1-adrenoceptor agonist phenylephrine elicited concentration-dependent contractile responses from preparations of bisected vas deferens and cauda epididymis. NECA (1 microM) potentiated responses to phenylephrine (< or = 1 microM) in the epididymal, but not in the prostatic half of the vas deferens. In preparations of epididymis NECA (1 microM) shifted phenylephrine concentration response curves to the left (4.6 fold). In the presence of a fixed concentration of phenylephrine (1 microM), NECA elicited concentration-dependent contractions of preparations of the epididymal half of the vas deferens and of the epididymis (pEC50 values 7.57+/-0.54 and 8.08+/-0.18, respectively). NECA did not potentiate responses to ATP in either the epididymal half of the vas deferens or the epididymis. 6. These studies are consistent with the action of stable adenosine analogues at prejunctional A1 and postjunctional A1-like adenosine receptors. The prejunctional A1 adenosine receptors only inhibit the electrically-evoked contractions of purinergic origin (an effect predominant in the prostatic half of the vas deferens). At the epididymis, where electrically-evoked contractions are entirely adrenergic, the predominant adenosine receptor agonist effect is a potentiation of alpha1-adrenoceptor-, but not of ATP-induced contractility.

Effects of lithium and myoinositol on the rat bisected vas deferens

1. 1. The effects of lithium (Li +) on the concentration-response curves (CRC) to norepinephrine (NE) and acetylcholine (Ach) on the bisected rat vas deferens (RVD) were investigated, as well as its action on the neuronal uptake of [ 3H] NE. 2. 2. Li + did not affect the 50% effective concentration (EC 50) of NE and Ach in the epididymal (EP) portion of the RVD. 3. 3. Li + caused a significant increase of the EC 50 to NE and Ach in the prostatic (PP) portion of the RVD. This shift to the right of the CRC to NE was prevented by the presence of myoinositol. 4. 4. Incubation of the PP of the RVD with Li +, increased the neuronal uptake of NE. The simultaneous incubation with myoinositol prevented this increase. 5. 5. After the pre-treatment of the rats with 6-hydroxydopamine (6-OHDA), or in the presence of cocaine, Li + failed to desensitize the PP of the RVD to NE. 6. 6. These results suggest that the effect of Li + on the PP of the RVD occurs mainly at the pre-synaptic level and may be related to the increase of neuronal uptake and to the interference of Li + on phosphatidylinositol hydrolysis.

Muscarinic receptor subtypes in the bisected vas deferens of the rat

1. 1. The nature of muscarinic receptor subtypes in the isolated prostatic and epididymal segments of the vas deferens of the rat were studied. 2. 2. Presynaptic receptors were characterized in segments under neurogenic transmural stimulation; postsynaptic receptors in segments without stimulation. 3. 3. The present work suggests that the potency of ACh required to activate muscarinic receptors is higher in the prostatic than in the epididymal segment. 4. 4. McN-A-343 was only able to induce dose-dependent contractions in the prostatic segment. 5. 5. The pA 2 value for 4-DAMP suggests that in the prostatic segment the postsynaptical ACh receptors seem to be pharmacologically similar to the ACh-M 3 subtype. 6. 6. Antagonism of the presynaptic ACh receptor subtype by pirenzepine supports the evidence that these receptors belong to the ACh-M 1 subtype.

Further examination of the inhibitory actions of α 1-adrenoceptor agonists in rat vas deferens

The inhibitory actions of α 1-adrenoceptor agonists were examined in the isolated bisected vas deferens of the rat. The calcium entry facilitator Bay K 8644 markedly potentiated the isometric contraction to a single stimulus pulse in epididymal portions of rat vas deferens: subsequent amidephrine produced an inhibition which was antagonised by the α 1-adrenoceptor antagonist, prazosin, but not by the α 2-adrenoceptor antagonist, yohimbine. The α 1-adrenoceptor agonists amidephrine and cirazoline failed to inhibit the transmitter overflow to trains of pulses at a frequency of 2 Hz in epididymal portions, but also failed to abolish the nifedipine-resistant adrenergic contraction to trains of pulses at 2 Hz in epididymal portions. It is concluded that α 1-adrenoceptor agonists have inhibitory effects which may be by action at presynaptic α 1-adrenoceptors.

Amphetamine-clonidine interaction on neurotransmission in the vas deferens of the rat

The interaction between amphetamine and clonidine on neurotransmission in the rat vas deferens was studied. In the whole vas deferens, clonidine 0.037 mumol/l displaced to the right the frequency-response curve evoked by either hypogastric or field stimulation. The frequency of stimulation that produced 50% of the maximal response (EF 50) was: control 4.0 Hz, clonidine 18.3 Hz (P less than 0.001 n = 4), for hypogastric nerve stimulation; and 2.1 Hz in controls and 17.1 Hz in clonidine-treated preparations, for field stimulation (P less than 0.001 n = 5). Preincubation with 5.4 mumol/l amphetamine antagonized the effect of clonidine (EF 50 amphetamine alone 6.2 Hz, amphetamine + clonidine 7.3 Hz; P greater than 0.5). After 12 min of incubation with clonidine 0.037 mumol/l the responses to 6.4 Hz (3 s, 0.5 ms) were decreased by 77 +/- 2.2%. Both yohimbine and amphetamine, in a concentration-dependent manner, attenuated the inhibition. Washout of clonidine produced a slow recovery of the responses. Inhibition of the motor response to nerve stimulation (6.4 Hz, 3 s) by 30 mumol/l 2',3'-cAMP was increased by 10 mumol/l dipyridamole and impaired by 100 mumol/l theophylline. Amphetamine, in a concentration that markedly reduced clonidine inhibition of neurotransmission failed to antagonize 2',3'-cAMP. In the bisected vas deferens clonidine inhibited the peak motor response to short trains of field stimuli in the prostatic portion ("non-adrenergic") and the sustained response in the epididymal portion ("adrenergic"). Yohimbine potentiated both types of responses and fully prevented the effect of clonidine. In the prostatic portion amphetamine slightly inhibited the peak motor response and attenuated the inhibitory effect of clonidine in both portions of the vas.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of calcium channel inhibitors on twitches and noradrenaline contractions of the rat bisected vas deferens

In the prostatic half of the rat vas deferens, responses to noradrenaline 30 μM were biphasic. Ca-deprivation reduced both phases. The initial part of the noradrenaline contraction was resistant to verapamil (IC 50 74.2 μM), methoxyverapamil (IC 50 ≈ 100 μM) and especially nifedipine (no effect up to 14.4 μM). The late part of this response and the entire response to noradrenaline in the epididymal half were abolished by verapamil (10.2 μM), methoxyverapamil (9.6 μM) or nifedipine (1.44 μM). The first phase of the twitch to single pulse transmural stimulation was abolished by nifedipine (14.4 μM) and inhibited by methoxyverapamil (57.6–96 μM); verapamil was less potent. The second phase of the twitch was totally resistant to nifedipine (14.4 μM), but more sensitive to inhibition by verapamil or methoxyverapamil than was the first. It was concluded that the calcium channel inhibitors can distinguish between three distinct types of calcium ion channel in the rat vas deferens: (1) sensitive calcium channels mediating the noradrenaline response in the epididymal half, and the late part of the noradrenaline response in the prostatic half (2) calcium channels responsible for the first phase of the twitch, blocked by high concentrations of nifedipine (3) calcium channels mediating the second phase of the twitch and the initial response to noradrenaline in the prostatic half, unaffected by nifedipine.