Effects of hydrogen sulfide on relaxation responses in the lower esophageal sphincter in rabbits: the potential role of potassium channels.

Hydrogen sulfide (H2S) is a significant physiologic inhibitory neurotransmitter. The main goal of this research was to examine the contribution of diverse potassium (K+) channels and nitric oxide (NO) in mediating the H2S effect on electrical field stimulation (EFS)-induced neurogenic contractile responses in the lower esophageal sphincter (LES). EFS-induced contractile responses of rabbit isolated LES strips were recorded using force transducers in organ baths that contain Krebs-Henseleit solutions (20 ml). Cumulative doses of NaHS, L-cysteine, PAG, and AOAA were evaluated in NO-dependent and NO-independent groups. The experiments were conducted again in the presence of K+ channel blockers. In both NO-dependent and NO-independent groups, NaHS, L-cysteine, PAG, and AOAA significantly reduced EFS-induced contractile responses. In the NO-dependent group, the effect of NaHS and L-cysteine decreased in the presence of 4-AP, and also the effect of NaHS decreased in the NO-dependent and independent group in the presence of TEA. In the NO-independent group, K+ channel blockers didn't change L-cysteine-induced relaxations. K+ channel blockers had no impact on the effects of PAG and AOAA. In addition, NaHS significantly relaxed 80-mM KCl-induced contractions, whereas L-cysteine, PAG, and AOAA did not. In the present study, H2S decreased the amplitudes of EFS-induced contraction responses. These results suggest that Kv channels and NO significantly contribute to exogenous H2S and endogenous H2S precursor L-cysteine inhibitory effect on lower esophageal sphincter smooth muscle.

The effects of different vasovasostomy techniques on motility of vas deferens (vas motility following vasovasostomy).

PURPOSE: Vasovasostomy is used to correct vas deferens (VD) transections encountered during surgery or to reverse sterilization vasectomies. Achieving vasal patency is the primary goal and the success is assessed on various factors including VD patency, flow rates, and pregnancy rates. While preserving vas motility is not a major concern in surgical practice, it is worth noting that VD has peristaltic activity which plays crucial role during ejaculation. Any disruption in its motility could potentially lead to negative outcomes in the future. We conducted an experimental study to assess vas motility changes following vasovasostomy. METHODS: The study was approved by Gazi University, Animals Ethic Committee. Twenty-four rats were allocated to four groups. Left-sided VD was harvested in control group (Gr1). The rest of the animals were subjected to transection of VD. Gr2 and 3 underwent microscopic and macroscopic anastomosis, respectively, while Gr4 underwent vasal approximation. After 12 weeks, all left-sided VD were resected, electrical field stimulation (EFS) and exogenous drugs were applied to induce contractions. Statistical analyses were performed and p value < 0.05 was regarded as statistically significant. RESULTS: The first and second phases of EFS-induced contractile responses(CR) increased for Gr3 and decreased for Gr4 at submaximal and maximal frequencies. An increase only at maximal frequency for second phase EFS-induced CR was encountered for Gr2. α-ß-methylene-ATP-induced CR decreased for Gr3 and 4. Noradrenaline-induced CR increased for Gr2, and 3 and decreased for Gr4. CONCLUSION: The results suggest that vasovasostomy performed using a surgical technique that minimizes disruption or damage to VD may have a favorable impact on motility.

Effects of cannabinoid and vanilloid receptor antagonists on nicotine induced relaxation response enhancement in rabbit corpus cavernosum.

Objectives: Endocannabinoids and nicotine regulate the neurotransmitter release in different central and peripheral synapses. Various studies in the literature demonstrate the interaction between endocannabinoid and nicotinic systems, especially in the central nervous system. The interaction between nicotinic and endocannabinoid systems was investigated in this study. We aimed to show the effects of cannabinoid and vanilloid receptor antagonists on nicotine-induced relaxation response increases in rabbit corpus cavernosum. Materials and Methods: From a total of seven male albino rabbits, three or four equal strips were cut from each corpus cavernosum and inserted in isolated organ baths. Tissues were contracted with phenylephrine (3×10-5 M). After contraction reached a plateau, strips were stimulated with EFS, and with the stabilization of EFS relaxation responses, 10-4 M of nicotine was administered to tissues. After that, in order to investigate the effects of AM251 (CB1 antagonist), AM630 (CB2 inverse agonist) or capsazepine (a vanilloid receptor antagonist) were given to different tissues, after the resting period. Results: Nicotine (10-4 M) increased the EFS-induced relaxation responses (14.60%±2.94%, P<0.05). AM630 decreased the enhancement of nicotine-induced EFS relaxation responses (nicotine 10-4 M enhancement: 17.16%±3.19%; nicotine 10-4 M enhancement in the presence of AM630 10-6 M: 4.44%±3.43% P<0.05; n=6), whereas effects of AM251 and capsazepine were not significant. Conclusion: In the present study, nicotine increased the amplitudes of EFS-induced relaxation responses probably via nicotinic acetylcholine receptors located on the nitrergic nerves of the corpus cavernosum. We showed the role of cannabinoid-like endo-ligands in nicotine-induced enhancement via CB2 receptors but not CB1 and VR1 receptors.

Enhancing effect of nicotine on electrical field stimulation elicited contractile responses in isolated rabbit bladder straight muscle; the role of cannabinoid and vanilloid receptors.

BACKGROUND: Nicotine acts as an agonist of nicotinic acetylcholine receptors (nAChR). These receptors belong to a superfamily of ligand-gated ion channels. We previously demonstrated that nicotine increased electrical field stimulation (EFS)-induced contractile or relaxation responses, possibly by facilitating neurotransmitter release from nerve terminals in various rabbit tissues. Studies have shown that there is an interaction between the endocannabinoid and nicotinic systems. This study aimed to investigate the interaction between nicotine and the endocannabinoid system in the rabbit urine bladder and also investigate the enhancing effect of nicotine on EFS-induced contractile responses in rabbit isolated bladder smooth muscle and its interaction with the endocannabinoid system. METHODS: The New Zealand albino male adult rabbits were used for this study. Following scarification, the urine bladder was rapidly excised, and then uniform strips were prepared. Each strip was mounted under 1 g isometric resting tension in an organ bath containing 20 mL of Krebs-Henseleit solution. After obtaining EFS-induced contractile responses, 10-4 M concentrations of nicotine were applied to the preparations, and EFS was stopped after 5 stimulations. Following washing, the same experimental procedure was performed with the same tissue in the presence of AM251 (a cannabinoid CB1R antagonist, 10-6 M), AM630 (a cannabinoid CB2R antagonist, 10-6 M), and capsazepine (a vanilloid receptor antagonist, 3 × 10-6 M). RESULTS: Nicotine enhanced the EFS-induced contraction responses by 17.16% ± 2.81% at a 4-Hz stimulation frequency. Cannabinoid receptor antagonists AM251 and AM630 reduced this increasing effect of nicotine although it was not significant and vanilloid receptor antagonist capsazepine did not significantly alter the nicotines' effect. DISCUSSION: These results show that enhancing effect of nicotine in the smooth muscle of the rabbit bladder, even though it was not significant endocannabinoid system possibly have a role in nicotines' effect.

Effects of epoxygenases on the nonadrenergic noncholinergic relaxant responses induced by electrical field stimulation in rabbit corpus cavernosum.

We aimed to investigate the effects of epoxygenases on electrical field stimulation (EFS)-mediated nitric oxide (NO)-dependent and NO-independent nonadrenergic noncholinergic (NANC) relaxations in isolated rabbit corpus cavernosum. The tissues of 20 male adult albino rabbits (2.5-3 kg) were suspended in organ baths containing aerated Krebs solution, and isometric contractions were recorded. EFS-mediated NANC relaxations were obtained on phenylephrin (3 × 10-5  M)-contracted tissues in the presence of guanethidine (10-6  M) and atropine (10-6  M). Miconazole (10-9 -10-4  M), 17-octadecynoic acid (ODYA) (10-10 -10-5  M), 14,15-epoxyeicosatrienoic acid (EET) (10-11 -10-8  M), 11,12-EET (10-12 -3 × 10-8  M) and 20-hydroxyeicosatetraenoic acid (HETE) (10-11 -3 × 10-8  M) were added cumulatively (n = 5-7 for each set of experiments). For NO-independent relaxations, Nω -nitro-l-arginine methyl ester (l-NAME) (10-4  M) was added before a group of experiments. Depending on the concentration, miconazole, 17-ODYA, 14,15-EET, 11,12-EET, and 20-HETE significantly enhanced both NO-dependent and NO-independent EFS-mediated relaxations (p < 0.05). Epoxygenases showed similar effect on NO-dependent and NO-independent relaxant responses except 20-HETE which caused significantly more enhanced relaxation on NO-dependent responses (p < 0.05). No drug caused a significant relaxation response on tissues contracted with phenylephrine. Epoxygenases contribute to EFS-mediated NO-dependent and NO-independent NANC relaxations by presynaptic mechanisms, offering a new treatment alternative for erectile dysfunction which needs to be explored in further in vivo, molecular and clinical studies.

Changes in cholinergic and nitrergic systems of defunctionalized colons after colostomy in rabbits.

BACKGROUND: This study was designed to assess smooth muscle function and motility in defunctionalized colonic segments and subsequent changes in pathways responsible for gastrointestinal motility. METHODS: Two-month-old New Zealand rabbits were randomly allocated into control and study groups. Sigmoid colostomies were performed in the study group. After a 2-month waiting period, colonic segments were harvested in both groups. For the in vitro experiment, the isolated circular muscle strips which were prepared from the harvested distal colon were used. First, contraction responses were detected using KCl and carbachol; relaxation responses were detected using papaverine, sodium nitroprusside, sildenafil, and l-arginine. The neurologic responses of muscle strips to electrical field stimulation (EFS) were evaluated in an environment with guanethidine and indomethacin. EFS studies were then repeated with atropine, Nω-nitro-l-arginine methyl ester, atropine, and Nω-nitro-l-arginine methyl ester-added environments. RESULTS: Although macroscopic atrophy had developed in the distal colonic segment of the colostomy, the contraction and relaxation capacity of the smooth muscle did not change. EFS-induced nitrergic-peptidergic, cholinergic-peptidergic, and noncholinergic nonnitrergic responses significantly decreased at all frequencies (0.5-32 Hz) in the study group compared with those in the control group (P < 0.05). CONCLUSIONS: Although the contraction capacity of the smooth muscle was not affected, the motility of the distal colon deteriorated owing to the defective secretion of presynaptic neurotransmitters such as acetylcholine, nitric oxide, and neuropeptides.

The effects of hydrogen sulfide on electrical field stimulation-induced neurogenic contractile responses in isolated rabbit lower esophageal sphincter: Contribution of nitrergic and non-adrenergic non-cholinergic transmission.

BACKGROUND: Hydrogen sulfide (H2S) is a gaseous signaling molecule that, similar to nitric oxide (NO), plays an important role as an inhibitor neurotransmitter in the digestive tract. This study aimed to investigate the effect of H2S and to identify neurogenic contraction responses dependent on the electrical field stimulation (EFS) in the isolated lower esophageal sphincters of rabbits. METHODS: An isolated lower esophageal sphincter was placed in an organ bath system and mechanical responses were recorded using a force transducer. The nerve-evoked contractile responses were obtained by EFS. The contractile responses were obtained as biphasic "on" and "off" phases seen at the beginning and end of EFS, respectively. RESULTS: Sodium hydrogen sulfide (NaHS) reduced the EFS-mediated "off" phase and the EFS-mediated non-adrenergic non-cholinergic (NANC) "off" phase. NaHS reduced the EFS-mediated "on" phase as well. l-Cysteine ​​reduced the EFS-mediated "off" phase and the EFS-mediated NANC "off" phase. l-Propargylglycine (PAG) did not affect the EFS-mediated "off" phase or the EFS-mediated NANC "off" phase. NaHS, l-cysteine, and PAG reduced the EFS-mediated, NO-independent "off" phase. The effect of NaHS in all of the experiments returned in time. Also, NaHS caused significant relaxation of 80-mM KCl-Krebs solution induced-contractions, while l-cysteine ​​and PAG did not cause a significant relaxation. CONCLUSION: These findings suggest that H2S has an inhibitory effect on the lower esophageal sphincter muscle. While the effect of H2S on EFS-mediated responses disappeared in time, the effect of H2S sustained the KCl-Krebs solution-induced contractions. This shows that H2S may have an effect on neurotransmission at the nerve terminal.

Effects of chronic l-DOPA administration on neurogenic and endothelium-dependent relaxation responses in rabbit corpus cavernosum.

BACKGROUND: Dopamine is a crucial central neurotransmitter that plays a fundamental role in the autonomic and somatic components of penile reflexes in animals and humans. Similar to the erectile responses of dopamine, systemic administration of l-DOPA induces yawning and penile erection in some species. The possible effects of l-DOPA on nitric oxide (NO)-dependent and -independent non-adrenergic non-cholinergic (NANC) relaxation responses mediated by electrical field stimulation (EFS) and endothelium-dependent relaxation were investigated in this study. METHODS: Thirty-two adult albino male rabbits, in two- and four-week-treatment groups, were divided into three subgroups: control group (saline-injected) (n=4), 3mg/kg/day (low dose) l-DOPA-injected groups (n=6) and 12mg/kg/day (high dose) l-DOPA-injected groups (n=6). After the intraperitoneal injection treatments, the corpus cavernosum tissues were placed in organ bath chambers. The EFS-mediated responses, and the concentration-response curve to carbachol, sodium nitroprusside (SNP), sildenafil were assessed. RESULTS: The two-week treatment with high-dose l-DOPA decreased the NO-dependent NANC relaxation responses, while there was no change in the low-dose two- and four-week treatment groups. The NO-independent NANC relaxation responses in the two-week groups decreased, and the responses in the four-week groups were unchanged when compared to the controls. The relaxation responses to carbachol showed no differences among all groups except for the high-dose four-week l-DOPA group. The relaxation responses of SNP and sildenafil were increased in all of the treatment groups when compared to the controls. CONCLUSIONS: The observed increases in SNP- and sildenafil-induced responses, along with the decreased EFS-mediated responses, suggest increased sensitivity in the NO-signalling pathway following l-DOPA administration.

Microwave-assisted synthesis and myorelaxant activity of 9-indolyl-1,8-acridinedione derivatives.

In this study a microwave-assisted method was applied for the synthesis of novel 9-(substituted indolyl)-3,4,6,7-tetrahydroacridine-1,8-(2H,5H,9H,10H)-dione derivatives. The structures of the compounds were confirmed by spectral methods including X-ray studies and elemental analysis. The Emax and pD2 values of the compounds and pinacidil were determined on noradrenaline precontracted tissues of isolated strips of rabbit gastric fundus smooth muscle. The obtained results indicated that some compounds and pinacidil produced concentration-dependent relaxation on the strips. The efficacy of compound 9 was higher than pinacidil. Docking studies were carried out to understand the interactions of the compounds with the active site of potassium channel. Methyl substituents on the acridine backbone and bromine atom on the indole ring led to more active compounds.

Chronic administration of fluoxetine impairs neurogenic and endothelium-dependent relaxation of the rabbit corpus cavernosum smooth muscle.

Antidepressants, including selective serotonin reuptake inhibitors (SSRIs), cause erectile dysfunction; however, the mechanism by which they cause erectile function is unclear. We investigated the reactivity of the corpus cavernosum after chronic fluoxetine treatment in rabbits. Twelve rabbits were randomly divided into two groups: control (n=6) or 20mg/kg/day of fluoxetine delivered i.p. (n=6). The reactivity of the corpus cavernosum tissue from the fluoxetine-treated and control groups was studied in organ chambers after 21 days of fluoxetine injection. In the fluoxetine-treated group, endothelium-dependent relaxation of the corpus cavernosum in response to acetylcholine was significantly decreased compared to the control group. However, the sensitivity (i.e., pD(2)) of the fluoxetine-treated cavernosal tissue strips to acetylcholine was not changed with respect to controls. Electrical field stimulation (EFS)-induced neurogenic relaxation was also significantly reduced in the fluoxetine-treated group. Relaxation in response to the nitric oxide (NO) donor sodium nitroprusside was similar between the cavernosal tissues from the two groups. There was also no change in agonist potency between the two groups. Additionally, chronic fluoxetine treatment had no effect on KCl-induced contractile responses. When tissue contraction was produced with phenylephrine to study relaxation in response to various stimuli, the tension induced was similar between the fluoxetine-treated and control groups. This study suggests that chronic fluoxetine treatment causes significant functional changes to the penile erectile tissue of rabbits, and these changes may contribute to the development of impotence.

A cannabinoid ligand, anandamide, exacerbates endotoxin-induced uveitis in rabbits.

PURPOSE: This study aimed to investigate the effects of anandamide or arachidonylethanolamide (AEA), an endogenous cannabinoid receptor agonist, on intraocular inflammation in an endotoxin-induced uveitis (EIU) model in rabbits. METHODS: Forty New Zealand albino male rabbits were used (5 groups, 8 animals in each). After establishment of sufficient anesthesia, animals were taken under surgery for intravitreal injections. A maximum amount of 50 µL of solution was injected into the central vitreous with a 30-gauge needle. In the control group, sterile saline was injected into the right eyes of the animals. Likewise, AEA (10(-5) M) in the second group, lipopolysaccharide (LPS; 100 ng) in the third group, and AEA (10(-5) M) and LPS (100 ng) in the fourth group were administered. Fifth group received 0.1 mL subtenon injection of AM251 (10(-5) M), a CB(1)-receptor antagonist, 30 min prior to intravitreal LPS (100 ng) and AEA (10(-5) M) injection. At 24 h after the surgical intervention, clinical evaluation was performed and animals were then euthanized with 100 mg/kg intravenous pentobarbital injections. Immediately after the induction of pentobarbital anesthesia, the anterior chamber of the eyes was quickly punctured using a 30-gauge needle to drain aqueous humor (AH) and obtained specimens were used for cell count, protein measurement, and microbiological contamination tests. After AH collection, enucleation was performed and enucleated material was kept for the pathological evaluation. RESULTS: AEA caused an overall worsening of EIU in studied eyes. It significantly increased the detrimental effects of endotoxin, as assessed by clinical investigation of ocular inflammation, AH leukocyte content, and AH protein concentrations. CB(1)-receptor antagonist AM251 administration reversed some components of this AEA-induced exacerbation to significant extents. CONCLUSION: AEA exacerbated EIU in rabbit eyes. AM251 has been found beneficial to prevent AEA's aggravating impact on EIU. As AEA is a treatment choice for lowering intraocular pressure in ophthalmology practice, concurrent use of CB(1)-receptor antagonists may be a questionable strategy in cases of secondary glaucoma, to avoid aggravation of the present inflammation.

Enhancement effects of nicotine on neurogenic relaxation responses in the corpus cavernosum in rabbits: the role of nicotinic acetylcholine receptor subtypes.

Nicotine acts as an agonist of nicotinic acetylcholine receptors, which belong to a superfamily of neurotransmitter-gated ion channels. We previously demonstrated that nicotine increases the electrical field stimulation (EFS)-evoked nitrergic relaxation responses via activation of nicotinic acetylcholine receptors. The aim of the present study is to investigate the subtypes of nicotinic acetylcholine receptors in rabbit corpus cavernosum. EFS-evoked relaxation responses were recorded from corpus cavernosum strips obtained from rabbits with an isometric force displacement transducers. Effects of nicotine on EFS-evoked relaxations were examined in pre-contracted tissues. Then the effect of nicotine on the EFS-evoked relaxations was examined in the presence of hexamethonium, dihydro-beta-erythroidine, mecamylamine or alpha-bungarotoxin. In our study, nicotine (3 x 10(-5), 10(-4)) transiently increased nitrergic relaxations induced by EFS in the rabbit isolated corpus cavernosum. While hexamethonium and mecamylamine near totally inhibited or abolished the neurorelaxation response to nicotine (3 x 10(-5)) on EFS, dihydro-beta-erythroidine and alpha-bungarotoxin partially inhibited these responses. These findings demonstrated that the alpha3-beta4, alpha4-beta2 and alpha7 subunits of nicotinic acetylcholine receptors play role on the nicotine-induced augmentation in EFS-evoked relaxation responses in rabbit corpus cavernosum.

Effect of a chloride channel inhibitor, 5-nitro-2- (3-phenylpropylamino)-benzoate, on endothelin-1 induced vasoconstriction in rabbit basilar artery.

AIM: Endothelin-1 (ET-1) has been implicated in the pathophysiology of cerebral vasospasm. Chloride (Cl-) channels exist in vascular smooth muscle and activation of these channels leads to depolarization and contraction. The aim of the present study was to test the effect of 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), a Cl- channel antagonist, on the ET-1-induced cerebral vasospasm in rabbit basilar artery and thus investigate the contribution of Cl- channels. MATERIAL AND METHODS: Thirty rabbits were divided into five groups and received intra-arterial injection of isotonic saline (Group I, n=6), ET-1 (group II, n=6), ET-1 plus NPPB (Group III, n=6), dimethylsulfate (DMSO4) (Group IV, n = 6) and NPPB (Group V, n=6). Pre and post injection basilar artery diameters were measured in each group and transmission electron microscopic investigations on basilar arteries were performed. RESULTS: The mean pre-injection and post-injection vessel diameters were 0.8833 mm and 0.7000 mm in ET-1 group, 0.6833 mm and 0.8500 mm in ET-1 + NPPB group. NPPB administered prior to ET-1 injection, prevented the ET-1-induced vasoconstriction. Additionally, NPPB prevents the ET-1 induced changes in vessel wall and neurons in the brain stem. CONCLUSION: The results of this study add further insights to our armamentarium against cerebral vasospasm.

Functional characterization of nonadrenergic noncholinergic neurotransmitter release via endocannabinoids: an in vitro study in rabbit corpus cavernosum.

INTRODUCTION: Corporal smooth muscle relaxation is mediated mainly but not completely by nitric oxide. Endocannabinoids modulate the various neurotransmitter systems. AIM: In the present study, a possible role of endocannabinoids on non-nitrergic nonadrenergic noncholinergic (NANC)-mediated relaxations was investigated. METHODS: In precontracted tissues, control electrical field stimulation (EFS)-induced NANC relaxation responses were obtained using varying frequencies of stimulation in the presence of L-arginine methyl ester (L-NAME), guanethidine, and atropine. To investigate the effects of cannabinoids on EFS-evoked non-nitrergic NANC relaxation responses, a similar experimental procedure was applied in the presence of cannabinoid receptor antagonists AM251 or AM630; vanilloid receptor antagonist capsazepine; or cannabinoid receptor agonists anandamide, arachidonyl-2-chloroethylamide (ACEA), or JHW015. MAIN OUTCOME MEASURES: Effects of cannabinoid receptor antagonists and agonists on EFS-evoked non-nitrergic NANC relaxation responses. RESULTS: L-NAME abolished EFS-induced relaxation responses at lower frequencies (2-4 Hz) and inhibited the relaxation responses at higher frequencies (8-32 Hz). AM251 and AM630 either together or separately inhibited, whereas anandamide, ACEA, and JHW015 enhanced non-nitrergic NANC relaxation responses. Anandamide did not alter EFS-induced non-nitrergic NANC relaxations in the presence of AM251 and AM630. Capsazepine enhanced non-nitrergic NANC relaxation responses. CONCLUSION: These results suggest that non-nitrergic NANC relaxations may be mediated partially by cannabinoid-like neuronal factors acting at both cannabinoid CB(1) and cannabinoid CB(2) receptors.

Role of nicotinic acetylcholine receptor subtypes on nicotine-induced neurogenic contractile response alternation in the rabbit gastric fundus.

Nicotine is a nonspecific agonist of nicotinic acetylcholine receptors. We previously demonstrated that nicotine increases the electrical field stimulation (EFS)-evoked contractile responses possibly by facilitating neurotransmitters release from nerve terminals by a mechanism dependent on the influx of Ca(2+) from voltage gated Ca(2+) channels via activation of nicotinic acetylcholine receptor. The aim of this study is to investigate subtypes of presynaptic nicotinic acetylcholine receptors involved in nicotine induced EFS-evoked contractile response alternation in the rabbit gastric fundus. EFS-evoked contractile responses were recorded from gastric fundus strips obtained from rabbits with isometric force displacement transducers. Effects of nicotine on EFS evoked contractions were examined. Then the effect of nicotine on the EFS-evoked contractions was examined in the presence of hexamethonium, dihydro-beta-erythroidine, mecamylamine or alpha-bungarotoxin. In our study, nicotine (10(-4), 3x10(-4) M) transiently increased neurogenic contraction induced by EFS in the rabbit isolated gastric fundus. While hexamethonium, dihydro-beta-erythroidine and mecamylamine inhibited the neurocontractile response to nicotine on EFS, alpha-bungarotoxin did not alter these responses. The pA(2) values of the antagonists were 4.67 (hexamethonium, n=8), 5.33 (dihydro-beta-erythroidine, n=8) and 5.43 (mecamylamine, n=8). These findings showed that the alpha3beta4 and alpha4beta2 subunits of nicotinic acetylcholine receptors play a role on the nicotine-induced augmentation in EFS-evoked contractile responses in rabbit gastric fundus.

Condensed 1,4-dihydropyridines with various esters and their calcium channel antagonist activities.

New alkyl 2,6,6-(2,7,7)-trimethyl-4-(2-fluoro-3-chloro-5-trifluoromethylphenyl)-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylates and 9-(3-chloro-2-fluoro-5-trifluoromethylphenyl)-6,6(7,7)-dimethyl-6,7-dihydrofuro[3,4-b]quinoline-1,8-diones have been synthesised and their calcium antagonistic activities on isolated rabbit sigmoid colon have been investigated and compared with Nifedipine. The investigation examined the influence of ester groups in the 3-position of the HHQ ring and the 2-methoxyethyl analogs were found to be the most active derivatives.

Lack of nitrate tolerance in isosorbid dinitrate- and sodium nitroprusside-induced relaxation of rabbit internal anal sphincter.

AIM: To investigate the tolerance development against the relaxant effect of nitric oxide donating drug isosorbide dinitrate (ISDN) and sodium nitroprusside (SNP) in internal anal sphincter (IAS) smooth muscle. METHODS: Relaxation responses of ISDN, and electrical field stimulation (EFS) were obtained before and after tolerance induction by ISDN incubation. RESULTS: ISDN (10(-7)-10(-4) mol/L) and SNP (10(-8)-10(-4) mol/L) caused a concentration-dependent relaxation on the basal tonus of the isolated rabbit IAS strips. After a period of 2 h incubation of the 6 multiply 10(-4) mol/L ISDN the relaxation effects of ISDN and SNP did not change compared to control strips. EFS evoked frequency-dependent relaxation in internal anal sphincter smooth muscle and E(max) obtained from control strips were not changed in ISDN tolerance-inducing condition. In this study nitrate tolerance was not observed in rabbit IAS smooth muscle. CONCLUSION: This result shows that nitric oxide donating drugs relaxes the internal anal sphincter of the rabbits without the development of tolerance.

Hydrogen peroxide and antioxidizing enzymes involved in modulation of transient facilitatory effects of nicotine on neurogenic contractile responses in rat gastric fundus.

Nicotine acts as an agonist of nicotinic acetylcholine receptors. Nicotinic acetylcholine receptors play a role in the modulation of neurotransmitter release in both the central and the peripheral nervous system. Moderate reactive oxygen species levels modulate the regulation of physiological functions e.g. neurotransmitter release. Previously in rabbit gastric fundus we demonstrated that nicotine transiently increased neurogenic contraction induced by electrical field stimulation (EFS). In this study we aimed to investigate the effects of hydrogen peroxide (H2O2), antioxidizing enzymes catalase and superoxide dismutase (SOD) on nicotine induced increases at cholinergic neurotransmission in rabbit gastric fundus. Although H2O2 did not alter nicotine induced transient neurogenic contractions at concentrations of 10(-6) and 10(-5) M, at high concentration (10(-4) M) H2O2 inhibited nicotine induced increases. Catalase (500 units/ml), enhanced the effect of nicotine but did not alter nicotine induced transient neurogenic contractions at the concentrations of 100 and 250 units/ml. SOD (75,150 and 225 units/ml) did not alter nicotine induced transient neurogenic contractions. In conclusion, at high concentration H2O2 (10(-4) M) inhibited nicotine's transient ability to augment neurogenic contractions and catalase (500 units/ml) enhanced the effect of nicotine.

Does tourniquet application alter the nitrergic responses of rabbit corpus cavernosum penis? A functional study.

OBJECTIVE: To investigate the effects of short and long periods of tourniquet application on corporal nerves, endothelium and smooth muscle responses. METHODS: After the rabbits were anesthetized with xylazine (5 mg/kg) and ketamine hydrochloride (35 mg/kg), a standard rubber circular band was applied to the base of the penis. After waiting for 20, 40 and 60 min, the tourniquets were removed and the penil tissue was reperfused for 5 min. In all groups, relaxation [carbachol, sodium nitroprusside (SNP) and electrical field stimulation (EFS) and contraction (phenylephrine and EFS)] responses were examined. In another set of experiments, the rabbits were killed 24 h after the tourniquet period of 60 min and carbachol-induced relaxation responses were obtained. RESULTS: SNP- and EFS-induced relaxation responses were similar in all groups. Carbachol-induced relaxation responses were not altered in tissues from 20 min tourniquet group, but they were significantly reduced in tissues from 40 and 60 min tourniquet group compared to that from control group. The impaired endothelium-mediated relaxation responses did not return to control levels after 24 h of reperfusion period. Neither phenylephrine nor EFS-mediated contraction responses were altered with tourniquet application. CONCLUSIONS: The results suggest that long period of tourniquet application altered endothelium-dependent muscarinic receptor-mediated relaxation responses. This is the first functional study that examined the effects of tourniquet application on corpus cavernosum tissue. In conclusion, it can be suggested that if tourniquet is necessary in penile surgery the application time of up to 20 min is more appropriate instead of prolonged usage.

The effects of varicocele and its surgical correction on vas deferens motility.

Varicocele is the abnormal dilation of venous pampiniform plexus and internal spermatic vein. Its prevalence in the adolescent period is almost equal to the prevalence of adult age. That is why the disease is accepted to appear in early adolescence and does not disappear spontaneously. Varicocele is established to be the most common cause of infertility in the adulthood period in terms of the testicular and/or epididymal damages it causes. Besides, malfunctioning of testis and/or epididymis cannot be blamed as the one and only reason of infertility. One major reason of the male infertility is vas deferens motility disorders. There is limited data in the literature investigating the effects of varicocele on the vas deferens motility. The aim of the study is to evaluate not only the motility defects of vas deferens for the period of varicocele, but also the effects of surgical varicocele correction on vas deferens motility. Thirty male Wistar-Albino rats were allocated to five groups. In the control group (Gr C, n = 6) bilateral vas deferens strips were harvested without any surgical intervention. Using the partial left renal vein obstruction technique, the experimental varicocele model was performed for the other four groups. Varicocele was apparent for these animals after the fourth week of the venous ligation. Bilateral vas deferens strips of varicocele group (Gr V, n = 6) were harvested. The rest of the animals having varicocele underwent relaparotomies. Three different surgical procedures were performed to these animals. The animals of group P (Gr P, n = 6) and group I (Gr I, n = 6) underwent Palomo and Ivanissevich procedures, respectively, for varicocele correction. And the animals of group S (Gr S, n = 6) underwent sham operation. After 4 weeks of relaparotomies, bilateral vas deferens strips of all three groups harvested. The electrical field stimulation (EFS) induced responses of all vas deferens strips as well as exogenous drug induced responses were recorded and analysed. The results of the study showed that the varicocele significantly inhibited the first phase of biphasic response of vas deferens in the ipsilateral side. However the correction of varicocele, free from surgical technique, ameliorated the affected first phase of EFS induced biphasic response in the ipsilateral side. The results of this study suggest that varicocele can be the reason of male infertility by not only causing testicular and/or epididymal damages but also triggering vas deferens motility defects. The correction of varicocele free from surgical technique may reverse the damaging of the vas deferens. Therefore when indicated surgical correction of varicocele is essential. It seems that varicocele surgery does not only prevent late term testicular and/or epididymal damages but also avoids vas deferens motility defects.