vasoactive-intestinal-peptide and linsidomine

We investigated whether the signal mechanism for relaxation may be affected by inflammation of the cat esophagus. Acute esophagitis was induced by perfusion with 0.1N HCI at a rate of 1 mL/min for 45 min over three consecutive days. We then isolated esophageal smooth muscle cells by enzymatic digestion with collagenase. We pre-contracted the isolated smooth cells with acetylcholine (ACh) (10(-5) M) and compared the agonist-induced relaxation of pre-con tracted normal cells with those of esophagitic cells. Vasoactive intestinal polypeptide (VIP) caused a dose-dependent relaxation in normal cells, and this curve was down shifted in esophagitic cells. Sodium nitroprusside (SNP) or SIN-1 (NO donor) produced dose-dependent relaxation in normal cells, which was not affected by esophagitis. 8-Br-cGMP (a cGMP ana log) also induced dose-dependent relaxation to a similar extent in both normal and esoph agitic cells. Forskolin (a cAMP activator) or db-cAMP (a cAMP analog) produced dose-dependent relaxation in normal cells, and this relaxation curve was down shifted in esoph agitic cells. Western blotting was used to determine what subtype of adenylyl cyclase was involved in the cAMP pathway. Western blot analysis of homogenates derived from esophageal smooth muscle using antibodies against adenylyl cyclase types II, III, IV and V/VI revealed the presence of type V and/or type VI only. This result suggests that relaxation via a cAMP-dependent pathway rather than a cGMP dependent-pathway is down regulated in cat acute esophagitis. This subsensitivity of the cAMP related pathway may be related to the activ ity of adenylyl cyclase V/VI.

Topics: Adenylyl Cyclases; Animals; Blotting, Western; Bucladesine; Cats; Cell Membrane Permeability; Colforsin; Cyclic AMP; Cyclic GMP; Dose-Response Relationship, Drug; Down-Regulation; Esophagitis; In Vitro Techniques; Isoenzymes; Molsidomine; Muscle Relaxation; Muscle, Smooth; Nitric Oxide Donors; Nitroprusside; Signal Transduction; Vasoactive Intestinal Peptide

1. We examined the role of the NO/cyclic GMP (cyclic GMP) pathway in nitric oxide (NO)- and vasoactive intestinal peptide (VIP)-induced relaxation of feline lower oesophageal sphincter (LES). Furthermore, it was studied whether methylene blue, LY83583 and ODQ, which are soluble guanylate cyclase (sGC) inhibitors, could inhibit NO-induced relaxation. 2. The nitric oxide synthase (NOS) inhibitor, N omega-nitro-L-arginine (L-NNA) had no effect in sodium nitropruside (SNP)-induced relaxation, but 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1)-induced relaxation was decreased by the pretreatment of L-NNA, which showed that SIN-1, not SNP, could activate NOS to cause relaxation. Methylene blue and LY83583 did not inhibit the relaxation by SNP and SIN-1. However, the more specific sGC inhibitor ODQ blocked the relaxation induced by NO donors. 3. To identify the relationship of NOS, sGC and adenylate cyclase in VIP-induced relaxation, tissue were pretreated with L-NNA and ODQ and SQ22536. These inhibitors produced significant inhibition of this response to VIP. The adenylyl cyclase inhibitor SQ 22536 also inhibited relaxation by VIP. 4. In conclusion, our data showed that SNP- and SIN-1-induced relaxation was mediated by sGC. Of sGC inhibitors, methylene blue and LY83583 were not adequate for the examination of NO donor-induced feline LES smooth muscle relaxation. VIP also caused relaxation by the pathway involving NO and cGMP and cAMP.

Topics: Aminoquinolines; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cats; Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Esophagogastric Junction; In Vitro Techniques; Indomethacin; Male; Methylene Blue; Molsidomine; Muscle Relaxation; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroprusside; omega-N-Methylarginine; Oxadiazoles; Quinoxalines; Signal Transduction; Vasoactive Intestinal Peptide

In accordance with the data reporting the identification of nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP) positive nerve fibres in the trabecular meshwork of the corpus cavernosum, we suggest that nitric oxide (NO) and VIP may serve complementary physiological roles in penile erection. Therefore SIN-1 and VIP were administered alone and in combination in an in vivo rabbit model. All rabbits revealed basal pressure values of 5-8 cm H2O intracavernously. In the rabbits intracavernously (i.c.) injected with SIN-1 alone and VIP alone, no adequate erectile responses were observed. Whereas, in the group intracavernously injected with the combination of SIN-1+VIP, erectile responses with mean maximal intracavernous pressure (max. ICP) 52.8 (+/-13.2) cm H2O were noted. These pressure elevations do not statistically diverge (P>0.05) than the ones obtained in the control group administered i.c. injections of the combination of papaverine/phentolamine (mean max. ICP 51 (+/-14.73) cm H2O). Referring to our results, we conclude that the combined use of SIN-1+VIP could play an important role in the physiological treatment of erectile dysfunction.

Topics: Animals; Drug Combinations; Injections; Male; Molsidomine; Nitric Oxide Donors; Penile Erection; Penis; Pressure; Rabbits; Vasoactive Intestinal Peptide; Vasodilator Agents

The interaction between nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) was investigated in isolated circular smooth muscle cells and strips of the guinea-pig gastric fundus. VIP induced a concentration-dependent inhibition of carbachol-induced contraction in smooth muscle cells with a maximum at 10(-6) M. The relaxation by 10(-6) M VIP was inhibited for 79.1+/-5.8% (mean+/-s.e. mean) by the NO-synthase (NOS) inhibitor L-N(G)-nitroarginine (L-NOARG; 10(-4) M) in a L-arginine reversible way. Also the inducible NOS (iNOS) selective inhibitor N-(3-(acetaminomethyl)-benzyl)acetamide (1400 W; 10(-6) M) inhibited the VIP-induced relaxation, but its inhibitory effect was not reversed by L-arginine. When cells were incubated with the guanylyl cyclase inhibitor 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ, 10(-6) M), the protein kinase A-inhibitor (R)-p-cyclic adenosine-3', 5'-monophosphothioate ((R)-p-cAMPS, 10(-6) M) and the glucocorticoid dexamethasone (10(-5) M), the relaxant effect of VIP was decreased by respectively 80.9+/-7.6, 77.0+/-11.6 and 87.1+/-4.5%. In circular smooth muscle strips of the guinea-pig gastric fundus, the VIP (10(-9) - 10(-7) M)-induced relaxations were not significantly influenced by 10(-4) M L-NOARG, 10(-6) M 1400 W, 10(-6) M ODQ and 10(-5) M dexamethasone. These results suggest that iNOS, possibly induced by the procedure to prepare the smooth muscle cells, is involved in the relaxant effect of VIP in isolated smooth muscle cells but not in smooth muscle strips of the guinea-pig gastric fundus. This study illustrates the importance of the experimental method when studying the influence of NOS inhibitors on the relaxation induced by VIP in gastrointestinal smooth muscle preparations.

Topics: Adenine; Adrenergic beta-Agonists; Animals; Atrial Natriuretic Factor; Carbachol; Colforsin; Cyclic AMP; Dexamethasone; Electric Stimulation; Enzyme Inhibitors; Gastric Fundus; Guinea Pigs; In Vitro Techniques; Isoproterenol; Molsidomine; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Nitroprusside; Pinacidil; Tetrodotoxin; Thionucleotides; Vasoactive Intestinal Peptide

1. Guanosine 3', 5'-cyclic monophosphate (cyclic GMP)-dependent kinase I (cGKI) is a major receptor for cyclic GMP in a variety of cells. Mice lacking cGKI exhibit multiple phenotypes, including severe defects in smooth muscle function. We have investigated the NO/cGMP- and vasoactive intestinal polypeptide (VIP)/adenosine 3', 5'-cyclic monophosphate (cyclic AMP)-signalling pathways in the gastric fundus of wild type and cGKI-deficient mice. 2. Using immunohistochemistry, similar staining patterns for NO-synthase, cyclic GMP- and VIP-immunoreactivities were found in wild type and cGKI-deficient mice. 3. In isolated, endothelin-1 (3 nM - 3 microM)-contracted, muscle strips from wild type mice, electrical field stimulation (1 - 16 Hz) caused a biphasic relaxation, one initial rapid, followed by a more slowly developing phase. In preparations from cGKI-deficient mice only the slowly developing relaxation was observed. 4. The responses to the NO donor, SIN-1 (10 nM - 100 microM), and to 8-Br-cyclic GMP (10 nM - 100 microM) were markedly impaired in strips from cGKI-deficient mice, whereas the responses to VIP (0.1 nM - 1 microM) and forskolin (0.1 nM - 1 microM) were similar to those in wild type mice. 5. These results suggest that cGKI plays a central role in the NO/cGMP signalling cascade producing relaxation of mouse gastric fundus smooth muscle. Relaxant agents acting via the cyclic AMP-pathway can exert their effects independently of cGKI.

Topics: Animals; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Electric Stimulation; Female; Fluorescent Antibody Technique; Immunohistochemistry; Male; Mice; Mice, Knockout; Molsidomine; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Receptor Cross-Talk; Signal Transduction; Stomach; Vasoactive Intestinal Peptide

We investigated whether nitric oxide (NO) exerts an inhibition on its own synthesis in the gastric myenteric plexus in rats. Nonadrenergic, noncholinergic relaxations in response to transmural electrical stimulation (TS) were markedly antagonized by NG-nitro-L-arginine methyl ester, (10(-4) M) and abolished by tetrodotoxin (10(-6) M). Pretreatment with various NO donors (3-morpholino-sydnonymide [SIN-1 (3 x 10(-7) to 3 x 10(-6) M)], S-nitroso-N-acetylpenicillamine (10(-6) to 10(-5) M), sodium nitroprusside (10(-8) to 3 x 10(-8) M) and 8-bromoquanosine 3', 5'-cyclic monophosphate [8-bromo-cGMP (10(-6) to 3 x 10(-6) M)]) significantly inhibited TS-evoked nonadrenergic, noncholinergic relaxations in a dose-dependent manner. In contrast, vasoactive intestinal polypeptide (10(-8) M)-induced relaxations were not affected by SIN-1 or 8-bromo-cGMP. TS evoked a significant increase in 3H-citrulline formation, which was completely abolished by calcium-free medium, NG-nitro-L-arginine methyl ester, (10(-4) M) and tetrodotoxin (10(-6) M). 3H-citrulline formation evoked by TS was significantly inhibited by SIN-1 (10(-7) to 10(-5) M) and 8-bromo-cGMP (10(-7) to 10(-5) M) in a dose-dependent manner. The inhibitory effect of SIN-1 was partially prevented by 1H-[1,2, 4]oxadiazolo[3,4-a]quinoxalin-1-one (10(-5) M), a guanylate cyclase inhibitor. We conclude that NO synthesis in the gastric myenteric plexus is negatively regulated by NO and cGMP. This suggests an autoregulatory feedback mechanism of NO synthesis in the gastric myenteric plexus.

Topics: Animals; Calcium Channels; Citrulline; Cyclic GMP; Dose-Response Relationship, Drug; Gastric Mucosa; Male; Molsidomine; Muscle Relaxation; Myenteric Plexus; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitroprusside; Rats; Rats, Sprague-Dawley; Stomach; Vasoactive Intestinal Peptide

The inhibitory innervation of guinea-pig urethral smooth muscle was investigated histochemically and functionally. The distribution of immunoreactivities to haem oxygenases (HO), neuronal NO synthase (nNOS), and vasoactive intestinal polypeptide (VIP) was studied, and the functional effects of the corresponding putative transmitters, CO, NO, and VIP, were assessed. HO-2 immunoreactivity was found in all nerve cell bodies of intramural ganglia, localized between smooth muscle bundles in the detrusor, bladder base and proximal urethra. About 70% of the ganglionic cell bodies were also NOS-immunoreactive (IR), whereas a minor part was VIP-IR. Some ganglion cells exhibiting tyrosine hydroxylase (TH) activity were demonstrated. Rich numbers of NOS-IR varicose nerve terminals could be found innervating the smooth muscle of the urethra, whereas VIP-IR terminals were less numerous. A rich number of TH-IR terminals were observed. The bladder showed a similar distribution of nerves, although only a few number of TH-IR nerves could be found. In bladder preparations exposed to sodium nitroprusside, cGMP-IR cells could be seen, forming an interconnecting network with long spindle-shaped processes. The cGMP-IR cells were especially abundant in the outer smooth muscle layers of the bladder, but less numerous in the urethra. In urethral strip preparations, electrical field stimulation evoked long-lasting frequency-dependent relaxations. The relaxations were not inhibited by the NO-synthesis inhibitor, L-NOARG, or enhanced by the NO-precursor, L-arginine. The haem precursor, 5-aminolevulinic acid (5-ALA), or the inhibitor of guanylate cyclase, ODQ, did not affect the urethral relaxations. Exogenously applied NO, SIN-1, and VIP relaxed the preparations by approximately 50%, whereas the relaxation evoked by exogenous CO was minor. These results suggest that CO probably is not involved in non-adrenergic, non-cholinergic inhibitory control of the guinea-pig urethra, where a non-NO/cGMP mediated relaxation seems to be predominant.

Topics: Animals; Carbon Monoxide; Cyclic GMP; Electric Stimulation; Enzyme Inhibitors; Female; Fluorescent Antibody Technique; Ganglia, Autonomic; Guinea Pigs; Heme Oxygenase (Decyclizing); Immunohistochemistry; Molsidomine; Nerve Tissue Proteins; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Sodium-Potassium-Exchanging ATPase; Urethra; Urinary Bladder; Vasoactive Intestinal Peptide; Xanthenes

Modulation of canine ileal pacemaker activity by nitric oxide (NO) or vasoactive intestinal peptide (VIP) was studied during recording of the intracellular electrical and mechanical activity from the entire muscularis externa and from an isolated circular muscle preparation both cut in the long axis of the circular muscle. In the whole-thickness preparation with cholinergic and adrenergic nerve function blocked, the inhibitory junction potentials (IJPs) recorded near the myenteric plexus (MyP) or deep muscular plexus (DMP) were abolished by omega-conotoxin GVIA (omega-CTX, 10(-7) to 3 x 10(-7) M), tetrodotoxin (TTX, 1 microM), or the NO synthase (NOS) inhibitor N omega-nitro-L-arginine (L-NNA at 50 microM). IJPs from electrical field stimulation triggered slow waves (TSWs); after TTX or omega-CTX, TSWs still occurred, advanced in time and increased in amplitude after TTX. Addition of L-NNA advanced the onset of the TSWs after omega-CTX. TTX, L-NNA, or omega-CTX left the resting membrane potentials, the characteristics of spontaneous slow waves, or TSWs evoked by a long stimulating pulse unchanged. L-NNA at 100 microM enhanced the amplitude but not the frequency of spontaneous slow waves. TTX and NOS blockers all increased circular muscle contractions associated with the spontaneous slow waves and TSWs. In isolated circular muscle preparations, the NOS inhibitors N omega-nitro-L-arginine methyl ester (L-NAME at 300 microM) or L-NNA at 100 microM abolished the IJPs and increased the regularity and amplitude of spontaneous slow waves and associated contractions, but TSWs could not be evoked before or after NOS inhibition. The NO donor 3-morpholinosydnonimine hydrochloride (SIN-1) at 200 microM caused hyperpolarizations (10-15 mV) similar to the IJP mediator, attenuated the IJPs, and abolished mechanical activities. SIN-1 increased the slow wave frequency but decreased the amplitude and duration of spontaneous slow waves and TSWs. VIP (10(-6) M) decreased contraction and slow wave amplitude and prolonged IJP duration without affecting membrane potential or slow wave frequency. We conclude that spontaneous slow waves and TSWs originate independently of neural activity. Pacemaking regions possess inhibitory neural inputs that release NO to mediate IJPs and relaxation and influence the delay before a TSW. NO (not VIP) release from nerves inhibits initiation of spontaneous slow waves or TSWs near the MyP, and spontaneous NO release modulates pacemaking activity f

Topics: Animals; Calcium Channel Blockers; Dogs; Electrophysiology; Enzyme Inhibitors; Female; Ileum; Male; Membrane Potentials; Molsidomine; Muscle Contraction; Nitric Oxide; Nitric Oxide Synthase; omega-Conotoxin GVIA; Peptides; Tetrodotoxin; Vasoactive Intestinal Peptide

The basal release of vasoactive intestinal polypeptide (VIP) from freshly prepared enriched synaptosomes was 159.1 +/- 17.3 fmol/mg protein (100%), which constituted 2.5% of the total VIP content. Basal VIP release was reduced by 65% by removal of external Ca2+. Release of VIP was stimulated by depolarization with KCl (65 mM, 143%) and in the presence of veratridine (10(-6) M, 184%), monensin (10(-5) M, 131%), and the Ca2+ ionophore A-23187 (10(-6) M, 160%). Stimulation of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent mechanisms using isoproterenol (10(-6)-10(-4) M) and forskolin (10(-6) and 10(-5) M) had no stimulatory influence on VIP release. In contrast, sodium nitroprusside (10(-4) M, 198%), the nitric oxide (NO) donor 3-(morpholino)sydnonimine (10(-4) M, 155%), and the guanosine 3',5'-cyclic monophosphate (cGMP) analogue 8-bromo cGMP (10(-4) M, 196%) caused a significant release of VIP. L-Arginine (10(-3) M, 246%) also caused a significant increase of VIP release that was antagonized by the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (5 x 10(-4) M, 131%), which had no effect when given alone. The results demonstrate that VIP can be released from enriched synaptosomes by Ca(2+)-dependent mechanisms by NO agonists or NO-dependent mechanisms. It is speculated that this VIP release is induced by a presynaptic stimulatory mechanism of NO and this effect could enhance or contribute to the action of NO.

Topics: Animals; Arginine; Calcium; Cell Fractionation; Cyclic GMP; Intestine, Small; Membrane Potentials; Molsidomine; NADPH Dehydrogenase; Nerve Endings; Nitric Oxide; Nitroprusside; Protein Kinase C; Rats; Rats, Wistar; Synaptosomes; Tetradecanoylphorbol Acetate; Vasoactive Intestinal Peptide

Nonadrenergic, noncholinergic (NANC) relaxations of airway smooth muscle are thought to be mediated by vasoactive intestinal peptide (VIP) and nitric oxide (NO). Previous studies of the parasympathetic innervation of guinea pig trachealis suggest that the ganglion neurons mediating NANC relaxations but not cholinergic contractions are associated with the esophagus. In this study, the location of the neurons mediating these responses and their neurochemical phenotype was further assessed. Guinea pig tracheas maintained in organotypic culture for 2 days with the adjacent esophagus intact displayed cholinergic contractions and NANC relaxations to electrical field stimulation (EFS) as well as VIP and NO synthase (NOS) nerve fiber densities that were similar to those of control tracheas. By contrast, in tracheas cultured without the esophagus, NANC relaxations to EFS were not observed, and VIP and NOS nerve fiber densities were reduced > 80%. EFS-induced cholinergic contractions were unaffected by esophagus removal. These results provide further evidence that NANC relaxations are mediated by VIP and NO coreleased from noncholinergic parasympathetic nerve endings derived from neurons intrinsic to the esophagus.

Topics: Analysis of Variance; Animals; Atropine; Electric Stimulation; Enzyme Inhibitors; Esophagus; Guinea Pigs; Male; Molsidomine; Muscle Contraction; Muscle Relaxation; Muscle, Smooth; Myenteric Plexus; Nerve Fibers; Neurons; Nitric Oxide Synthase; Nitroarginine; Organ Culture Techniques; Parasympathetic Nervous System; Trachea; Vagus Nerve; Vasoactive Intestinal Peptide

Since vasoactive intestinal peptide (VIP) and nitric oxide (NO) are considered to be non-adrenergic, non-cholinergic (NANC) inhibitory mediators in human penile erectile tissue, the goal of this study was to discover possible synergistic effects of exogeneous VIP and the NO donor 3-morpholino-sydnonimine (SIN-1) in human isolated cavernous arteries and cavernosal smooth muscle. In contrast to VIP, SIN-1 elicited complete and reproducible relaxant actions. Combined administration of VIP and SIN-1 revealed non-synergistic, independent relaxant effects in both investigated tissues. The results do not favour a combined administration of VIP and SIN-1 as a new therapeutic approach in the treatment of erectile dysfunction.

Topics: Arteries; Drug Interactions; Humans; In Vitro Techniques; Isometric Contraction; Male; Molsidomine; Muscle Relaxation; Muscle, Smooth; Muscle, Smooth, Vascular; Penis; Phenylephrine; Regional Blood Flow; Vasoactive Intestinal Peptide; Vasodilator Agents

1. We have investigated the correlation between relaxation and changes in cyclic nucleotide content of human tracheal smooth muscle (HTSM) in vitro following inhibitory non-adrenergic non-cholinergic (i-NANC) neural bronchodilator responses evoked by electrical field stimulation (EFS), and compared these with changes seen with sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1) and vasoactive intestinal peptide (VIP). The effects of N omega-nitro-L-arginine methyl ester (L-NAME), Methylene Blue and alpha-chymotrypsin (alpha-CT) were studied. 2. EFS (10 Hz, 1 ms, 40 V for 30 s) evoked a time-dependent relaxation accompanied by a concurrent rise in cGMP, both of which were maximal at 30 s and unaffected by epithelium removal. Levels of cAMP were more variable than those of cGMP and were not significantly changed at any time point. 3. SIN-1 (1 mM) and SNP (100 microM) also produced time-dependent relaxations which were maximal between 2 and 8 min, accompanied by concomitant rises in cGMP; however, these changes were larger than those associated with i-NANC relaxations. cAMP levels were unchanged at all time points. 4. EFS-evoked i-NANC relaxations and cGMP increases (time, t = 30 s) were inhibited by L-NAME. The effects were partially reversed by L-arginine (1 mM), but not by D-arginine. D-NAME and alpha-CT (2 u ml-1) had no effect on either relaxation or cGMP accumulation. Tetrodotoxin (TTX, 3 microM) inhibited both relaxation and cGMP accumulation. 5. VIP (1 microM) also produced a time-dependent relaxation associated with a concurrent rise in cAMP levels with no change in cGMP levels. 6. Methylene Blue (10 microM) partially inhibited EFS (10 Hz)-evoked i-NANC relaxation and cGMP accumulation, and almost completely inhibited both relaxation and cGMP accumulation evoked by SIN-1 (1 mM). Methylene Blue had no significant effect on relaxation or cGMP accumulation evoked by SNP (100 microM). 7. Neural i-NANC relaxations in HTSM are associated with a concurrent selective accumulation of cGMP which is unaffected by epithelium removal. This is inhibited in a stereoselective manner by L-NAME and mimicked by SNP and SIN-1; however, cGMP accumulation was greatly increased with SNP and SIN-1 suggesting compartmentalized changes in cGMP content. VIP also caused relaxation associated with an increase of cAMP; however, no evidence was found for VIP being involved in i-NANC relaxation. Hence nitric oxide (NO), or a NO-containing complex, appears to mediate i-NANC

Topics: Adenosine Monophosphate; Adolescent; Adult; Arginine; Bronchoconstriction; Child; Chymotrypsin; Cyclic GMP; Electric Conductivity; Epithelium; Female; Humans; Male; Methylene Blue; Middle Aged; Molsidomine; Muscle, Smooth; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitroprusside; Tetrodotoxin; Time Factors; Trachea; Vasoactive Intestinal Peptide; Vasodilator Agents

The effects of pretreatment with the nitric oxide (NO)-releasing substances 3-morpholino-sydnoninime (SIN-1) and nitroglycerin were investigated on relaxations induced by non-adrenergic non-cholinergic (NANC) nerve stimulation, authentic NO and vasoactive intestinal polypeptide (VIP) in the rat gastric fundus. Short periods of electrical stimulation (0.5-16 Hz, 1 ms, pulse trains of 10 s) induced frequency-dependent transient relaxations, previously shown to be mainly mediated by NO. Both SIN-1 (10-100 microM) and nitroglycerin (0.5 mM) pretreatment significantly reduced these electrically induced responses to a similar extent as the inhibitor of the NO biosynthesis L-nitroarginine (30-300 microM). Prolonged periods of electrical stimulation (16 Hz, 1 ms, pulse trains of 180 s) induced a sustained relaxation, previously shown to be mediated by NO and VIP. L-Nitroarginine (30-300 microM) or pretreatment with SIN-1 (100 microM) or nitroglycerin (0.5 mM) did not affect the amplitude of this relaxation but slowed down its onset. Authentic NO (0.01-10 microM) and VIP (0.01-10 nM) induced respectively transient and sustained concentration-dependent relaxations. SIN-1 or nitroglycerin pretreatment had no effect on the concentration-response curves to NO and VIP. These results indicate that prolonged exposure to NO donors inhibits electrically induced nerve-mediated NANC relaxations without affecting the postjunctional response to NO and VIP. As similar results are obtained with NO biosynthesis inhibitors, our results illustrate a prejunctional inhibitory effect of NO on the NANC nerves of the rat gastric fundus and suggest the presence of an autoregulatory mechanism for the nitrergic innervation.

Topics: Animals; Autonomic Nervous System; Electric Stimulation; Feedback; Gastric Fundus; In Vitro Techniques; Isometric Contraction; Male; Molsidomine; Muscle Relaxation; Muscle, Smooth; Nitric Oxide; Nitroglycerin; Rats; Rats, Wistar; Vasoactive Intestinal Peptide; Vasodilator Agents

Human isolated central (5 to 12 mm) and peripheral (< 2 mm) bronchi were contracted with 3 microM histamine. Relaxations were then evoked by electrical field stimulation (EFS) (1 to 32 Hz, 1 ms, 12 V for 15 s in the presence of indomethacin, atropine, and propranolol). The magnitude, time-course, and frequency-response relationship of these nonadrenergic, noncholinergic (NANC) relaxations were similar in the central and the peripheral airways. NG-Nitro-L-arginine (L-NOARG) (10 microM) inhibited the tetrodotoxin-sensitive NANC relaxations in both central and peripheral bronchi, whereas the stereoisomer D-NOARG was without effect. This inhibition was reversed by L-arginine (1 mM) but not be D-arginine (1 mM). The nitric oxide donor compound, 3-morpholinosydnonimine (SIN-1), was equipotent at relaxing the central and peripheral airways. Vasoactive intestinal peptide (VIP), although it relaxed central airways, was virtually ineffective in relaxing the peripheral airways. In addition, the peptidase, alpha-chymotrypsin, at a concentration that blocked relaxations to VIP, was without effect on NANC relaxations in the central bronchi. The results support the following hypotheses: (1) both central and peripheral airways receive nonadrenergic relaxant innervation; (2) the relaxant response to electrical stimulation of this system is dependent on a pathway involving L-arginine; and (3) the relaxant response does not appear to involve VIP, but it may involve the production of nitric oxide.

Topics: Arginine; Bronchi; Chymotrypsin; Electric Stimulation; Humans; In Vitro Techniques; Molsidomine; Muscle Relaxation; Nitroarginine; Stereoisomerism; Vasoactive Intestinal Peptide; Vasodilator Agents