The effects of varying Mg2+ ion concentrations on contractions to the cotransmitters ATP and noradrenaline in the rat vas deferens.

The vas deferens responds to a single electrical pulse with a biphasic contraction caused by cotransmitters ATP and noradrenaline. Removing Mg2+ (normally 1.2 mM) from the physiological salt solution (PSS) enhances the contraction. This study aimed to determine the effect of Mg2+ concentration on nerve cotransmitter-mediated contractions. Rat vasa deferentia were sequentially bathed in increasing (0, 1.2, 3 mM) or decreasing (3, 1.2, 0 mM) Mg2+ concentrations. At each concentration a single field pulse was applied, and the biphasic contraction recorded. Contractions to exogenous noradrenaline 10 µM and ATP 100 µM were also determined. The biphasic nerve-mediated contraction was elicited by ATP and noradrenaline as NF449 (10 µM) and prazosin (100 nM) completely prevented the respective peaks. Taking the contractions in normal PSS (Mg2+ 1.2 mM) as 100%, lowering Mg2+ to 0 mM enhanced the ATP peak to 170 ±â€¯7% and raising Mg2+ to 3 mM decreased it to 39 ±â€¯3%; the noradrenaline peak was not affected by lowering Mg2+ to 0 mM (97 ±â€¯3%) but was decreased to 63 ±â€¯4% in high Mg2+ (3 mM). Contractions to exogenous ATP, but not noradrenaline, were increased in Mg2+ 0 mM and both were inhibited with Mg2+ 3 mM. Changing Mg2+ concentration affects the contractions elicited by the cotransmitters ATP and noradrenaline. The greatest effects were to potentiate the contraction to ATP in Mg2+ 0 mM and to inhibit the contraction to both ATP and noradrenaline in high Mg2+. Future publications should clearly justify any decision to vary the magnesium concentration from normal (1.2 mM) values.

The distribution of nerves supplying the testis, epididymis and accessory sex glands of Suncus murinus.

Chronic testicular pain remains an important challenge for urologists. Investigation of the innervation of male gonads thus becomes essential for deepening our understanding of their regulatory roles in male reproductive physiology and pathophysiology. Studies of testicular innervation are mainly limited to the intratesticular peptidergic nerves of the testis by immunohistochemical and acetylcholinesterase histochemical investigations in some animals. Little is known about the detailed, overall distribution in general experimental animal testis. In this study, the distribution of nerves supplying the testis, epididymis and accessory sex glands of Suncus murinus was investigated by whole mount immunohistochemistry staining using a neurofilament protein antibody. Testicular nerves arose through three routes: nerves deriving from the mesenteric and renal plexuses accompanied the testicular artery, entering into the testicular hilum through the superior ligament of the testis. The nerves originating from the hypogastric plexus then ran along the internal iliac artery, deferential artery, and passed through the mesoductus deferens or mesoepididymis, innervating the cauda and corpus of the epididymis, the vas deferens and the inferior pole of the testis. The third route arose from the pelvic plexus, distributed in the seminal vesicle and the prostate. The density of nerve fibers was higher in the cauda epididymidis than in the testis, and more abundant in the vas deferens. The different origins and distribution densities of testicular nerves in S. murinus may serve different neuronal regulatory functions, and, therefore, S. murinus may be an important model animal for understanding the different characteristics of testicular pain.

[Anatomic application of the genitofemoral nerve in uroandrological surgery].

The genitofemoral nerve (GFN) has its unique anatomic characteristics of location, run and function in the male urinary system and its relationship with the ureter, deferens and inguinal region is apt to be ignored in clinical anatomic application. Clinical studies show that GFN is closely correlated with postoperative ureteral complications and pain in the inguinal region after spermatic cord or hernia repair. GFN transplantation can be used in the management of erectile dysfunction caused by cavernous nerve injury. Therefore, GFN played an important role in the clinical application of uroandrology. This review summarizes the advances in the studies of GFN in relation to different diseases in uroandrology.

[Blood vessels and nerves surrounding the seminal vesicles: A clinical anatomic study].

OBJECTIVE: To investigate the precise locations of the blood vessels and nerves surrounding the seminal vesicles (SV) in men and provide some anatomical evidence for SV-related minimally invasive surgery. METHODS: We observed the courses and distribution of the blood vessels and nerves surrounding SVs and obtained the data for positioning the SV neuroplexes in 20 male pelvises. RESULTS: One branch of the neuroplexes was distributed to the SVs bilaterally with the neurovascular bundles, (2.85 ± 0.18) cm from the median sulcus of the prostate (MSP), while another branch ran through the Denonvillier fascia behind the SV, (0.81 ± 0.06) cm from the MSP. The arterial SVs (ASV) originated from the inferior vesical artery and fell into 4 types, 55% going directly to the SVs as one branch, 15% running between the SV and the ampulla of the deferent duct as another branch, 25% downward as 2 branches to the SV and between the SV and the ampulla of the deferent duct respectively, and 5% as the other ASVs. The shortest distance from the ASV through the prostatic neuroplexus to the posterior SV was (1.08 ± 0.09) cm. CONCLUSION: In SV resection, neuroplexus injury can be reduced with a bilateral distance of < 2.85 cm and a posterior distance of < 0.81 cm from the MSP, and so can bleeding by vascular ligation between the SV and the ampulla of the deferent duct.

Increase of angiotensin-converting enzyme activity and peripheral sympathetic dysfunction could contribute to hypertension development in streptozotocin-induced diabetic rats.

Diabetes augments the risk of hypertension. Although several factors have been implicated in the development of such hypertensive state, we designed this study to investigate blood pressure development, the activity of angiotensin-converting enzyme (ACE) in blood as well as sympathetic neurotransmission in the vas deferens of diabetic rats. We used streptozotocin (STZ)-induced diabetic rats (60 mg/kg) in order to evaluate the systolic blood pressure (SBP), ACE activity and peripheral sympathetic neurotransmission. We observed the following changes of parameters: increase of SBP, decrease of heart rate, augmentation of plasma ACE activity, enhancement of phasic and tonic vas deferens contractions elicited by electrical stimulation at 5 Hz, increase of maximal response to noradrenaline (NA) and decrease of adenosine triphosphate (ATP)-elicited contraction of vasa deferentia. The results reveal that in the development of hypertension in diabetic rats, augmentation of circulating ACE activity precedes the sympathetic dysfunction. Additionally, it seems that the purinergic and noradrenergic neurotransmission is compromised.

Microsurgical subinguinal varicocelectomy in children, adolescents, and adults: surgical anatomy and anatomically justified technique.

Microsurgical varicocelectomy has become the gold standard in adults because of low recurrence and postoperative hydrocele rates; it is increasingly applied in children and adolescents. This review aims to provide the surgeon with the necessary surgical anatomy of the spermatic cord and with a step-by-step, anatomically justified description of technique, toward clearer comprehension and improved application. The anatomic compartments of the spermatic cord are delineated by the external and internal spermatic fasciae. Venous drainage of testis-epididymis is accomplished by the internal spermatic, deferential, and external spermatic (cremasteric) veins. All 3 anastomose at the caudal pole of testis, and then via gubernacular veins with the posterior scrotal veins. Another anastomosis exists between a cremasteric branch and anterior scrotal veins, which gives the external pudendal vein. Subinguinal approach offers access to varicose spermatic veins and collaterals. Use of surgical microscope offers identification of small veins, preservation of arteries, lymphatics, and nerves, and appreciation of spermatic cord fasciae, which permits the development of two surgical planes. In the surgical plane of internal spermatic vessels, internal spermatic veins are ligated, whereas the testicular artery and innervation, as well as lymphatics, are preserved. In the plane of cremasteric vessels and vas, cremasteric veins are ligated, whereas the cremasteric artery, vas deferens and its vasculature, lymphatics, and the genital branch of genitofemoral nerve are preserved. Delivery of the testis to ligate gubernacular veins is at the discretion of the surgeon. Finally, venous return is effected by deferential and scrotal veins, or, when gubernacular veins are ligated, by deferential veins only.

Subsequent alterations in the contractile property of the vas deferens according to duration of spermatic cord torsion.

OBJECTIVE: To determine whether twisting of the ipsilateral vas deferens results in alteration of its contractility. DESIGN: Experimental study. SETTING: University animal lab. ANIMAL(S): 24 male Wistar rats. INTERVENTION(S): All the rats in the experimental groups underwent spermatic cord torsion. Durations of torsion were 45 minutes, 3 hours, and 24 hours in groups 2, 3, and 4, respectively. In groups 2 and 3, subgroups b were created to evaluate late effects using in vitro pharmacological techniques. MAIN OUTCOME MEASURE(S): The contractility of the vas deferens was evaluated in groups 1, 2a, 3a, and 4 right after and in groups 2b and 3b 48 hours after the initial operation. RESULT(S): Group 4 and subgroups 2b and 3a had significantly diminished responses compared with the control group, whereas in subgroups 2a and 3b, the responses to noradrenaline and to single-pulse field stimulation were not significantly different. CONCLUSION(S): The impairment of contractility with the twisting of the vas deferens might be another factor responsible for subfertility, particularly that related to sperm transport. The unfavorable late change in short duration of torsion may be the result of either ischemia and reperfusion injury or sympathetic overactivation in the acute period of torsion.

Role of Ca(2+)-activated K(+) channels and Na(+),K(+)-ATPase in prostaglandin E(1)- and E(2)-induced inhibition of the adrenergic response in human vas deferens.

We studied the role of K(+) channels and Na(+),K(+)-ATPase in the presynaptic inhibitory effects of prostaglandin E(1) (PGE(1)) and PGE(2) on the adrenergic responses of human vas deferens. Furthermore, we determined the effects of increasing extracellular K(+) concentrations ([K(+)](o)) and inhibition of Na(+),K(+)-ATPase on neurogenic and norepinephrine-induced contractile responses. Ring segments of the epididymal part of the vas deferens were taken from 45 elective vasectomies and mounted in organ baths for isometric recording of tension. The neuromodulatory effects of PGEs were tested in the presence of K(+) channel blockers. PGE(1) and PGE(2) (10(-8) to 10(-6)M) induced inhibition of adrenergic contractions. The presence of tetraethylammonium (10(-3)M), charybdotoxin (10(-7)M), or iberiotoxin (10(-7)M), prevented the inhibitory effects of PGE(1) and PGE(2) on the adrenergic contraction. Both glibenclamide (10(-5)M) and apamin (10(-6)M) failed to antagonize PGE(1) and PGE(2) effects. Raising the [K(+)](o) from 15.8mM to 25.8mM caused inhibition of the neurogenic contractions. Ouabain at a concentration insufficient to alter the resting tension (10(-6)M) increased contractions induced by electrical stimulation but did not alter the contractions to norepinephrine. The inhibition of neurogenic responses induced PGE(1), PGE(2) and increased extracellular concentration of K(+) was almost completely prevented by ouabain (10(-6)M). The results demonstrate that PGE(1) and PGE(2) inhibit adrenergic responses by a prejunctional mechanism that involves the activation of large-conductance Ca(2+)-activated K(+) channels and Na(+),K(+)-ATPase.

Mechanisms involved in nicotinic acetylcholine receptor-induced neurotransmitter release from sympathetic nerve terminals in the mouse vas deferens.

Prejunctional nicotinic acetylcholine receptors (nAChRs) amplify postganglionic sympathetic neurotransmission, and there are indications that intraterminal Ca(2+) stores might be involved. However, the mechanisms by which nAChR activation stimulates neurotransmitter release at such junctions is unknown. Rapid local delivery (picospritzing) of the nAChR agonist epibatidine was combined with intracellular sharp microelectrode recording to monitor spontaneous and field-stimulation-evoked neurotransmitter release from sympathetic nerve terminals in the mouse isolated vas deferens. Locally applied epibatidine (1 µM) produced 'epibatidine-induced depolarisations' (EIDs) that were similar in shape to spontaneous excitatory junction potentials (SEJPs) and were abolished by nonselective nAChR antagonists and the purinergic desensitizing agonist α,ß-methylene ATP. The amplitude distribution of EIDs was only slightly shifted towards lower amplitudes by the selective α7 nAChR antagonists α-bungarotoxin and methyllcaconitine, the voltage-gated Na(+) channel blocker tetrodotoxin or by blocking voltage-gated Ca(2+) channels with Cd(2+). Lowering the extracellular Ca(2+) concentration reduced the frequency of EIDs by 69%, but more surprisingly, the Ca(2+)-induced Ca(2+) release blocker ryanodine greatly decreased the amplitude (by 41%) and the frequency of EIDs by 36%. Ryanodine had no effect on electrically-evoked neurotransmitter release, paired-pulse facilitation, SEJP frequency, SEJP amplitude or SEJP amplitude distribution. These results show that activation of non-α7 nAChRs on sympathetic postganglionic nerve terminals induces high-amplitude junctional potentials that are argued to represent multipacketed neurotransmitter release synchronized by intraterminal Ca(2+)-induced Ca(2+) release, triggered by Ca(2+) influx directly through the nAChR. This nAChR-induced neurotransmitter release can be targeted pharmacologically without affecting spontaneous or electrically-evoked neurotransmitter release.

The residual nonadrenergic contractile response to nerve stimulation of the mouse prostate is mediated by acetylcholine but not ATP in a comparison with the mouse vas deferens.

Neuronal release of noradrenaline is primarily responsible for the contraction of prostatic smooth muscle in all species, and this forms the basis for the use of α(1)-adrenoceptor antagonists as pharmacotherapies for benign prostatic hyperplasia. Previous studies in mice have demonstrated that a residual nonadrenergic component to nerve stimulation remains after α(1)-adrenoceptor antagonism. In the guinea pig and rat prostate and the vas deferens of guinea pigs, rats, and mice, ATP is the mediator of this residual contraction. This study investigates the mediator of residual contraction in the mouse prostate. Whole prostates from wild-type, α(1A)-adrenoceptor, and P2X1-purinoceptor knockout mice were mounted in organ baths, and the isometric force that tissues developed in response to electrical field stimulation or exogenously applied agonists was recorded. Deletion of the P2X1 purinoceptor did not affect nerve-mediated contraction. Furthermore, the P2-purinoceptor antagonist suramin (30 µM) failed to attenuate nerve-mediated contractions in wild-type, α(1A)-adrenoceptor, or P2X1-purinoceptor knockout mice. Atropine (1 µM) attenuated contraction in prostates taken from wild-type mice. In the presence of prazosin (0.3 µM) or guanethidine (10 µM), or in prostates taken from α(1A)-adrenoceptor knockout mice, residual nerve-mediated contraction was abolished by atropine (1 µM), but not suramin (30 µM). Exogenously administered acetylcholine elicited reproducible concentration-dependent contractions of the mouse prostate that were atropine-sensitive (1 µM), but not prazosin-sensitive (0.3 µM). Acetylcholine, but not ATP, mediates the nonadrenergic component of contraction in the mouse prostate. This cholinergic component of prostatic contraction is mediated by activation of muscarinic receptors.

Dynamic monitoring of NET activity in mature murine sympathetic terminals using a fluorescent substrate.

BACKGROUND AND PURPOSE: To validate a fluorescence approach for monitoring norepinephrine transporter (NET) transport rate in mature sympathetic terminals, and to determine how prejunctional muscarinic receptors affect NET rate. EXPERIMENTAL APPROACH: Confocal imaging of a fluorescent NET substrate [neurotransmitter transporter uptake assay (NTUA)] as it accumulates in the mature sympathetic nerve terminals of the mouse isolated vas deferens. Fluorescence recovery after photobleaching (FRAP), enhanced green fluorescence protein (EGFP)-transgenic mice and contraction studies were also used. KEY RESULTS: NTUA fluorescence accumulated linearly in nerve terminals, an effect that was prevented with NET inhibition with desipramine (1 microM). Such accumulation was reversed by amphetamine (10 microM), which is known to reverse the direction of transport of NET substrates. NTUA labelling was not present in cholinergic terminals (identified using EGFP fluorescence expressed in transgenic mice under a choline acetyltransferase promoter). FRAP experiments, altered nerve terminal distribution with reserpine pretreatment and co-imaging in terminals filled with a cytoplasmic marker (Alexa 594 dextran) indicated that the NTUA labelling was largely confined to vesicles within varicosities; vesicular exchange between varicosities was rare. The rate of NTUA accumulation was slower in the presence of the muscarinic agonist carbachol (10 microM) demonstrating muscarinic inhibition of NET rate. CONCLUSIONS AND IMPLICATIONS: A straightforward protocol now exists to monitor NET transport rate at the level of the single nerve terminal varicosity, providing a useful tool to understand the physiology of NET regulation, the action of NET inhibitors on mature sympathetic terminals, dynamic vesicular tracking and to identify sympathetic terminals from mixed terminal populations in living organs.

Effects of T-type calcium channel blockers and thalidomide on contractions of rat vas deferens.

BACKGROUND AND PURPOSE: In rat vas deferens, nerve mediated-contractions to a single electrical stimulus consist of an early purinergic and a later adrenergic component with differing sensitivities to L-type calcium channel blockers. We have investigated the effects of the T-type calcium channel blockers mibefradil and (1S, 2S)-2-[2-[[3-(1H-benzimidazol-2-yl)propyl]methylamino]ethyl]-6-fluoro-1,2,3,4-tetrahydro-1-(1-methylethyl)-2-naphthalenyl cyclopropanecarboxylic dihydrochloride (NNC 55-0396) against contractions in rat vas deferens. In addition, the actions of thalidomide were examined. EXPERIMENTAL APPROACH: Prostatic and epididymal portions of rat vas deferens were stimulated with a single electrical stimulus every 5 min, and mouse whole vas deferens was stimulated with 40 pulses at 10 Hz every 5 min. KEY RESULTS: Both mibefradil and NNC 55-0396 (100 microM) produced inhibition of contractions of epididymal portions (42 +/- 13%, n= 7, and 43 +/- 4%, n= 15, of control respectively). However, both agents produced small inhibitions of responses in prostatic portions, presumably by L-type calcium channel block. Thalidomide (100 microM) inhibited contractions in epididymal (55 +/- 4% of control, n= 17) but not in prostatic portions of rat vas deferens. Thalidomide (10-100 microM) also inhibited contractions in mouse vas deferens. CONCLUSIONS AND IMPLICATIONS: The T-type calcium channel blockers mibefradil and NNC 55-0396 block particularly the adrenoceptor-mediated, nifedipine-resistant response to nerve stimulation in rat vas deferens, and this may suggest that this component involves T-type calcium channels. In addition, thalidomide has actions that resemble those of the T-type calcium channel blockers, in that it blocks nifedipine-resistant contractions in epididymal portions.

Vas deferens--a model used to establish sympathetic cotransmission.

The vas deferens has been used as a model for many diverse studies of different aspects of autonomic neurotransmission since its introduction including, in particular, sympathetic cotransmission involving release of ATP and neuropeptide Y together with noradrenaline and prejunctional and postjunctional neuromodulation. It has also been used to study sympathetic reinnervation following vasectomy and castration, as well as the deleterious effects of diabetes, hypertension and chronic alcohol.

Inmunohistoquímica de la inervación del conducto deferente humano / Immunohistochemistry in the innervations of the human vas deferens

El conducto deferente humano presenta una pared muscular gruesa, donde el componente muscular liso ocupa la parte media y más prominente. Esta composición histológica le permite al órgano desarrollar las potentes contracciones durante el proceso de la eyaculación y emisión del semen. Objetivos: Analizar la presencia y distribución de la positividad inmunohistoquímica a Neurofilamentos (NF) en las paredes del conducto deferente humano. Pacientes, Materiales y Método: De tres pacientes sometidos a orquiectomía radical por diagnóstico de Seminoma, se obtuvieron los conductos deferentes fijados en formol tamponado (pH 7,2). Mediante procedimientos histológicos de rutina, se obtuvieron secciones de 5 um de espesor en portaobjetos silanizados. Se procedió al desarrollo del protocolo de inmunohistoquímica usando anticuerpos específicos contra Neurofilamentos (NF); las imágenes se obtuvieron con cámara fotográfica digital CCD Micrometrics, en microscopio óptico Olympus CX31. Resultados: En los subcompartimientos de las secciones transversales de la pared de los conductos deferentes humanos, se observa la reacción inmunohistoquímica positiva a NF. Sin embargo, los fascículos nerviosos se concentran en la adventicia, mientras que en la mucosa y pared muscular son en extremo escasos y finos. Conclusión: En el conducto deferente existe una inervación preferencial dispuesta en la adventicia del órgano, siendo posible que la potencia de la contracción de la pared en base a la actividad muscular, requiera factores adicionales de estimulación.

The human vas deferens has a thick muscular wall, where the smooth muscle component occupies the middle and most prominent. This composition allows the organ histologic develop powerful contractions during ejaculation process and the semen. Objectives. To analyze the presence and distribution of immunologically positlve for Neurofilament (NF) on the walls of human vas deferens. Patients, Materiall and Methods.' Three patients undergoing radical orchiectomy for seminoma diagnosis were obtained vas deferens fixed in buffered formain (pH 12). By routine histological procedures, sections were obtained 5 um thick on silylated slides. We proceeded to the development of immunohistochemical protocol using specific antibodies against Neurofilament (NF); the digitized images were obtained with CCO Micrometrics digital camera, in the light microscope Olympus CX31. Results: In the subcompartments of the cross sections of the wall of human vas deferens, there is a positive immunohistochemical reaction to NF However, nerve bundles are concentrated in the adventitia, whereas in the mucosa and muscle wall are extremely rare and fine. Conclusion: In the vas deferens there willing preferential innervation in the adventitia of the court, it being possible for the power of contraction of the wall of the body based on muscle activity, stimulation requires additional factors.

Alpha2 adrenoceptors modulate histamine release from sympathetic nerves in the guinea pig vas deferens.

In our previous studies, we have identified that histamine (HA) is co-released with noradrenaline (NA) from the sympathetic nerve terminals and acts as a novel sympathetic neurotransmitter. However, the modulation of sympathetic HA release by sympathetic prejunctional receptors is still unknown. Therefore, in this study, we explored the modulation effect of alpha(2) adrenoceptors on sympathetic HA release and the interaction of alpha(2) adrenoceptors with HA H(3) receptors in vas deferens isolated from guinea pig. The selective alpha(2) adrenoceptor agonist brimonidine decreased the HA overflow in a concentration-dependent manner and abolished the contractile responses mediated by sympathetic HA release. Yohimbine competitively blocked the effect of brimonidine on HA release. Similarly, the HA H(3) receptor agonist R-(alpha)-methylhistamine also decreased HA release, and thioperamide blocked the effect of R-(alpha)-methylhistamine. When used singly, both yohimbine and thioperamide facilitated HA release. In addition, the inhibitory effect of brimonidine on HA release was stronger in the presence of thioperamide, while it was reduced when HA H(3) receptors were activated by R-(alpha)-methylhistamine. Our findings indicate for the first time that sympathetic HA release is negatively modulated both by prejunctional alpha(2) receptors and HA H(3) receptors and that these two prejunctional receptors interact with each other in modulating sympathetic HA release.

High spatial resolution studies of muscarinic neuroeffector junctions in mouse isolated vas deferens.

It is acknowledged that neurotransmission in the mouse vas deferens is predominantly mediated by ATP and noradrenaline (NA) released from sympathetic nerves while cholinergic transmission in the rodent vas deferens is often overlooked despite early literature. Recently we have characterized a cholinergic component of neurogenic contraction of mouse isolated vas deferens. In the present paper, by confocal imaging of Ca(2+) dynamics we detected acetylcholine (ACh) action at muscarinic cholinergic neuroeffector junctions at high-resolution. Experiments were carried out in the presence of prazosin (100 nM) and alpha,beta methylene ATP (alpha,beta-MeATP) (1 microM) to inhibit responses to NA and ATP respectively. Exogenous ACh (10 microM) elicited Ca(2+) transients, an effect blocked by the muscarinic receptor antagonist, cyclopentolate (1 microM). Ca(2+) transients were evoked by electrical stimulation of intrinsic nerves in the presence of the cholinesterase inhibitor neostigmine (10 microM). Stimulation produced a marked increase in the frequency and number of Ca(2+) transients. Cyclopentolate reduced the frequency of occurrence of spontaneous and evoked events to control levels. The alpha(2)-adrenoceptor antagonist yohimbine (300 nM) did not affect the spontaneous Ca(2+) transients, but increased the frequency of occurrence of evoked transients, an effect inhibited by cyclopentolate. The postjunctional effects of neuronally-released ACh are limited by the action of cholinesterase. Release of ACh appears to be tonically inhibited by NA released from sympathetic nerve terminals through action at prejunctional alpha(2)-adrenoceptors. Tetrodotoxin (TTX, 300 nM) abolished the nerve-evoked Ca(2+) events, with no effect on Ca(2+) transients elicited by exogenous ACh. In conclusion, the presence of spontaneous and evoked cholinergic Ca(2+) transients in smooth muscle cells of the mouse isolated vas deferens has been revealed. These events are mediated by ACh acting at M(3) muscarinic receptors. This action stands in marked contrast to the lack of effect of neuronally-released NA on smooth muscle Ca(2+) dynamics in this tissue.

Allosteric interaction of the anticholinergic drug [N-(4-phenyl)-phenacyl-l-hyoscyamine] (Phenthonium) with nicotinic receptors of post-ganglionic sympathetic neurons of the rat vas deferens.

Phenthonium (Phen), a quaternary analog of hyoscyamine, is a blocker of muscarinic activity and an allosteric blocker of alpha(1)2betagammaepsilon nicotinic receptors. Specifically, Phenthonium increases the spontaneous release of acetylcholine at the motor endplate without depolarizing the muscle or inhibiting cholinesterase activity. This paper compares Phenthonium's effects on sympathetic transmission and on ganglionic nicotinic receptor activation. Neurotransmitter release and twitch of the rat vas deferens were induced either by electrical stimulation or by 1,1-dimethyl-4-phenylpiperazine (DMPP) activation of nicotinic receptors. Contractions independent of transmitter release were induced by noradrenaline and adenosine 5'-triphosphate (ATP). Phenthonium inhibited transmitter release and depressed twitch without changing the responsiveness to noradrenaline or ATP. Twitch depression did not occur after K(+)-channel blockade with 4-aminopyridine (4-AP) or charybdotoxin. DMPP had a similar effect, but high concentrations induced contraction of non-stimulated organs. Incubation of Phenthonium inhibited further DMPP twitch depression and non-competitively depressed the contractile responses elicited by DMPP. Furthermore, mecamylamine, but neither methyllycaconitine nor atropine, blocked the contraction elicited by DMPP. Phenthonium and DMPP are K(+)-channel openers that primarily inhibit sympathetic transmission. Contraction induced by DMPP was probably mediated by neuronal nicotinic receptor other than the alpha7 subtype. The blockade of DMPP contractile response was unrelated to Phenthonium's antimuscarinic or K(+)-channel opening activities. Since Phenthonium's quaternary chemical structure limits its membrane diffusion, the non-competitive inhibition of DMPP excitatory responses should be linked to allosteric interaction with neuronal nicotinic receptors that putatively qualify Phenthonium as a novel modulator of cholinergic synapses.

5-HT antagonists NAN-190 and SB 269970 block alpha2-adrenoceptors in the guinea pig.

Serotonin (5-HT) plays a significant role in the regulation of intestinal secretion of water and electrolytes. The initial aim of this study was to use intracellular recording and specific antagonists to identify roles of 5-HT1A and 5-HT7 receptors of submucosal noncholinergic secretomotor neurons of guinea pig ileum, in vitro. However, it was found that the widely used 5-HT receptor antagonists NAN-190 (5-HT1A) and SB 269970 (5-HT7) both blocked alpha2-adrenoceptors, and hence depressed inhibitory synaptic potentials and hyperpolarizations evoked by noradrenaline, in these neurons. Both compounds enhanced neurally evoked contractions of the guinea pig vas deferens, an effect characteristic of blockade of alpha2-adrenoceptors. These results raise significant concerns about studies using NAN-190 and SB 269970 as specific antagonists of serotonin receptors.

Mechanisms of adaptive supersensitivity in vas deferens.

Adaptive supersensitivity is a phenomenon characteristic of excitable tissues and discloses as a compensatory adjustment of tissue's response to unrelated stimulatory endogenous and exogenous substances after chronic interruption of excitatory neurotransmission. The mechanisms underlying such higher postjunctional sensitivity have been postulated for a variety of cell types. In smooth muscles, especially the vas deferens with its rich sympathetic innervation, the mechanisms responsible for supersensitivity are partly understood and appear to be different from one species to another. The present review provides a general understanding of adaptive supersensitivity and emphasizes early and recent information about the putative mechanisms involved in this phenomenon in rodent vas deferens.

Reinnervation of transplanted vas deferens by cholinergic nerves normally supplying skeletal muscle.

The rat vas deferens was removed and either transplanted alongside the soleus muscle or into the bed of the soleus muscle that had previously been removed, and in this case the soleus nerve was connected to the transplant. The vas deferens reinnervated by the somatomotor nerve recovered the best. Contractions to transmural electrical stimulation could not be elicited from the denervated vas deferens, although noradrenaline and acetylcholine elicited contractions. The reinnervated vas deferens produced good contractile responses to transmural stimulation, and these were substantially reduced by a cholinergic muscarinic blocking agent, hyoscine, as compared to only a small reduction in the control vas deferens. Neostigmine potentiated the contraction of the transplanted vas deferens to a greater extent than that of the control. This indicated that a substantial component of the contractile response was produced by cholinergic fibres. Consistent with this was the finding that, while guanethidine blocked a greater proportion of the contraction in the control vas deferens, the contraction of the reinnervated transplant was less affected. Acetylcholine elicited a strong contraction in control vas deferens, but only a small response was obtained in the reinnervated transplant. However, the response to noradrenaline was greater in the transplant than in the control vas deferens. These results indicate that cholinergic nerves normally supplying skeletal muscle can reinnervate smooth muscle and that the alien somatomotor innervation altered the responsiveness of the smooth muscle of the vas deferens. Morphological studies confirm the shift from adrenergic to cholinergic fibres in the reinnervated vas deferens.