cyclic-gmp and 7-nitroindazole

Topics: Animals; Antidepressive Agents; Arginine; Cyclic GMP; Depression; Dizocilpine Maleate; Glucagon-Like Peptide 2; Indazoles; Male; Methylene Blue; Mice; Motor Activity; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Phosphodiesterase 5 Inhibitors; Receptors, N-Methyl-D-Aspartate; Serine; Signal Transduction; Sildenafil Citrate; Swimming

Considering the pivotal role of nitric oxide (NO) pathway in depressive disorders, the aim of the present study was to investigate the antidepressant-like effect of selegiline in mice forced swimming test (FST), and possible involvement of NO-cyclic guanosine monophosphate (cGMP) pathway in this action.. After assessment of locomotor activity in open-field test, mice were forced to swim individually and the immobility time of the last 4min was evaluated. All drugs were given intraperitoneally (ip).. Selegiline (10mg/kg) decreased the immobility time in the FST similar to fluoxetine (20mg/kg). Pretreatment with l-arginine (NO precursor, 750mg/kg) or sildenafil (a phosphodiesterase 5 inhibitor, 5mg/kg) significantly reversed the selegiline anti-immobility effect. Sub-effective dose of selegiline (1mg/kg) showed a synergistic antidepressant effect with NG-nitro-l-arginine methyl ester (L-NAME, inhibitor of NO synthase, 10mg/kg) or 7-nitroindazole (specific neuronal NO synthase inhibitor, 30mg/kg), but not with aminoguanidine (specific inducible NO synthase inhibitor, 50mg/kg). Pretreatment of mice with methylene blue (an inhibitor of NO synthase and soluble guanylyl cyclase, 10mg/kg) significantly produced a synergistic response with the sub-effective dose of selegiline. Neither of the drugs changed the locomotor activity. Also, hippocampal and prefrontal cortex (PFC) nitrite content was significantly lower in selegiline-injected mice compared to saline-administrated mice. Also, co-injection of 7-nitroindazole with selegiline produced a significant reduction in hippocampal or PFC nitrite contents.. It is concluded that selegiline possesses antidepressant-like effect in mice FST through inhibition of l-arginine-NO-cyclic guanosine monophosphate pathway.

Topics: Animals; Antidepressive Agents; Arginine; Cyclic GMP; Drug Synergism; Fluoxetine; Guanidines; Hippocampus; Immobility Response, Tonic; Indazoles; Male; Methylene Blue; Mice; Motor Activity; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitrites; Prefrontal Cortex; Selegiline; Signal Transduction; Sildenafil Citrate; Swimming

The goal of the study was to investigate the effects of drugs modifying L-arginine:NO:cGMP pathway on the development of tolerance to flunitrazepam (FNZ)-induced motor impairment in mice. FNZ-induced motor incoordination was assessed on the 1st and 8th days of experiment, using the rotarod and chimney tests. It was found that (a) both a non-selective nitric oxide synthase (NOS) inhibitor: N

Topics: Animals; Arginine; Cyclic GMP; Drug Interactions; Drug Tolerance; Flunitrazepam; Indazoles; Male; Mice; Motor Skills; NG-Nitroarginine Methyl Ester; Nitric Oxide; Signal Transduction; Sildenafil Citrate

In the current study, the involvement of N-methyl-d-aspartate receptor (NMDAR) and nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) system in the antidepressant-like effects of baclofen was evaluated by using animal model in forced swimming test. Followed by an open field test for the evaluation of locomotor activity, the immobility time for mice in force swimming test was recorded. Only the last four min was analyzed. Administration of Baclofen (0.5 and 1mg/kg, i.p.) reduced the immobility interval in the FST. Prior administration of l-arginine (750mg/kg, i.p.,) a nitric oxide synthase substrate or sildenafil (5mg/kg, i.p.) a phosphodiesterase 5 into mice suppressed the antidepressant-like activity of baclofen (1mg/kg, i.p.).Co-treatment of 7-nitroindazole (50mg/kg, i.p.,) an inhibitor of neuronal nitric oxide synthase, L-NAME (10mg/kg, i.p.,) a non-specific inhibitor of nitric oxide synthase or MK-801 (0.05mg/kg, i.p.) an NMDA receptor antagonist with subeffective dose of baclofen (0.1mg/kg, i.p.), reduced the immobility time in the FST as compared to the drugs when used alone. Co-administrated of lower doses of MK-801 (0.01mg/kg) or l-NAME (1mg/kg) failed to effect immobility time however, simultaneous administration of these two agents in same dose with subeffective dose of baclofen (0.1mg/kg, i.p.), minimized the immobility time in the FST. Thus, our results support the role of NMDA receptors and l-arginine-NO-GMP pathway in the antidepressant-like action of baclofen.

Topics: Animals; Antidepressive Agents; Arginine; Baclofen; Cyclic GMP; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Indazoles; Male; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Phosphodiesterase 5 Inhibitors; Receptors, N-Methyl-D-Aspartate; Signal Transduction; Sildenafil Citrate; Stress, Psychological; Swimming

Wuling mycelia powder is the dry powder of rare a fungi Xyla ria sp., Carbon species, with a long history of medicinal use in Chinese medicine. Recently it has shown a powerful antidepressant activity in clinic.. The present study explores the antidepressant activity of Wuling mycelia powder in chronic unpredictable mild stress (CUMS) rats and its possible involvement of l-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signaling pathway.. Experiments were performed in the rat CUMS model. CUMS rats were treated with Wuling mycelia powder (0.5, 1.0 or 2.0 g/kg, i.g.) to test behavioral changes including the sucrose preference, the crossing number and food consumption. Further, L-arginine (substrate for nitric oxide) (750 mg/kg), 7-nitroindazole (a specific neuronal nitric oxide synthase inhibitor) (25 mg/kg), sildenafil (phosphodiesterase 5 inhibitor) (5 mg/kg) and methylene blue (direct inhibitor of both nitric oxide synthase and soluble guanylate cyclase) (10 mg/kg) were treated for 60 min before each test to detect the possible mechanism of antidepressant-like effect of Wuling mycelia powder.. After 4 weeks of administration, both 1.0 or 2.0 g/kg Wuling mycelia powder suppressed the behavioral changes including the sucrose preference [F(3, 31)=50.87, p<0.001], the crossing number [F(3, 31)=68.98, p<0.05], and food consumption [F(3, 31)=19.04, p<0.05] in the CUMS rats. The antidepressant-like effect of Wuling mycelia powder was prevented by pretreatment with l-arginine and sildenafil. Pretreatment of rats with 7-nitroindazole and methylene blue potentiated the effect of Wulin mycelia powder.. Our findings demonstrate that Wuling mycelia powder has an antidepressant-like effect in the CUMS rats, and possible involvement of L-arginine-nitric oxide-cyclic GMP signaling pathway in its antidepressant effect.

Topics: Animals; Antidepressive Agents; Arginine; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Feeding Behavior; Food Preferences; Hippocampus; Indazoles; Male; Methylene Blue; Mycelium; Nitric Oxide; Powders; Rats, Sprague-Dawley; Signal Transduction; Sildenafil Citrate; Stress, Psychological; Sucrose

Clinical and preclinical data reported that ascorbic acid has antidepressant properties. The present study was designed to investigate the participation of l-arginine-NO-cGMP pathway in the antidepressant-like effect of ascorbic acid in the tail suspension test (TST) in mice. The antidepressant-like effect of ascorbic acid (1mg/kg, p.o.) in the TST was prevented by the pre-treatment of mice with NMDA (0.1pmol/site, i.c.v.), l-arginine (750mg/kg, i.p., a substrate for nitric oxide synthase) or sildenafil (5mg/kg, i.p., a phosphodiesterase 5 inhibitor). The administration of MK-801 (0.001mg/kg, i.p), 7-nitroindazole (25mg/kg, i.p., a neuronal nitric oxide synthase inhibitor) or ODQ (30pmol/site i.c.v., a soluble guanylate cyclase inhibitor) in combination with a sub-effective dose of ascorbic acid (0.1mg/kg, p.o.) reduced the immobility time in the TST test when compared with either drug alone. None of the results in the TST appears to be due to a nonspecific locomotor effect. Our findings provide evidence that the effect of ascorbic acid in the TST involve an interaction with NMDA receptors and l-arginine-NO-cGMP pathway, contributing to the understanding of the mechanisms underlying the antidepressant-like effect of this vitamin.

Topics: Animals; Antidepressive Agents; Arginine; Ascorbic Acid; Cyclic GMP; Depression; Disease Models, Animal; Dizocilpine Maleate; Enzyme Inhibitors; Exploratory Behavior; Female; Hindlimb Suspension; Indazoles; Mice; N-Methylaspartate; Nitric Oxide; Oxadiazoles; Piperazines; Purines; Quinoxalines; Signal Transduction; Sildenafil Citrate; Sulfones

1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol is a novel putative trace amine receptor modulator hypothesized to be useful for treatment-resistant depression. In our previous study, we have demonstrated the antidepressant-like effect of this molecule in mouse forced swim and tail suspension tests and shown to act via modulating the levels of norepinephrine, serotonin and dopamine. The present study attempts to explore the involvement of l-arginine-nitric oxide-cyclic guanosine monophosphate pathway in the antidepressant-like effect of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol in the mouse forced swim test. The antidepressant-like action of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol (8 mg/kg, i.p) was reversed by pretreatment with L-arginine (750 mg/kg, i.p.), a nitric oxide precursor. In contrast, pretreatment with methylene blue (a soluble guanlyate cyclase inhibitor and nitric oxide synthase (NOS) inhibitor) or 7-nitroindazole (a specific neuronal NOS inhibitor) potentiated the antidepressant-like effect of sub-effective dose of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol (2mg/kg, i.p.) in this test model. Furthermore, the antidepressant-like effect of this molecule (8 mg/kg, i.p.) was reversed by sildenafil (5mg/kg, i.p.), a phosphodiesterase inhibitor. In conclusion, the antidepressant-like action of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol involved L-arginine-nitric oxide-cyclic guanosine monophospate signaling pathway.

Topics: Analysis of Variance; Animals; Antidepressive Agents; Arginine; Biogenic Amines; Brain Chemistry; Cyclic GMP; Cyclohexanols; Depression; Guanylate Cyclase; Indazoles; Isoquinolines; Male; Methylene Blue; Mice; Motor Activity; Neurotransmitter Agents; Nitric Oxide; Nitric Oxide Synthase; Phosphodiesterase Inhibitors; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Sulfones; Swimming

The L-arginine/nitric oxide (NO)/cGMP pathways have been implicated in the control of a variety of physiological mechanisms and are believed to participate in the modulation of anxiety in the CNS. The aim of this study was to investigate the effects of N(G)-nitro-L-arginine-methyl-ester (L-NAME), a non-selective inhibitor of NO synthase (NOS); 7-nitroindazole (7-NI), a preferential inhibitor of neuronal NOS; and sodium nitroprusside (SNP), an NO donor, administered into the ventral hippocampus (VH) of rats submitted to the elevated T-maze (ETM). The ETM, an animal model derived from the elevated plus-maze, allows the measurement of two defensive behavioral responses in the same rat: inhibitory avoidance and escape. Results showed that L-NAME and 7-NI impaired the acquisition of inhibitory avoidance and prolonged escape latency in the ETM, suggesting an anxiolytic-like and panicolytic-like effect, respectively. SNP facilitated the acquisition of inhibitory avoidance without interfering with escape performance, suggesting an anxiogenic-like effect. Treatment with methylene blue did not alter per se any of the behavioral responses measured in the ETM, but blocked the effect promoted by SNP. Thus, altogether these results suggest that NO in the VH is critically involved in the modulation of defensive behavior of rats exposed to the ETM.

Topics: Analysis of Variance; Animals; Anti-Anxiety Agents; Anxiety; Avoidance Learning; Behavior, Animal; Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Escape Reaction; Exploratory Behavior; Hippocampus; Indazoles; Male; Methylene Blue; Motor Activity; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroprusside; Rats; Rats, Wistar; Staining and Labeling

Lithium is still the mainstay in the treatment of affective disorders as a mood stabilizer. Lithium also shows some anticonvulsant properties. While the underlying mechanisms of action of lithium are not yet exactly understood, we used a model of clonic seizure induced by pentylenetetrazole (PTZ) in male NMRI mice to investigate whether the anticonvulsant effect of lithium is mediated via NO-cGMP pathway. Injection of a single effective dose of lithium chloride (25 mg/kg) intraperitoneally (i.p.) increased significantly the seizure threshold (P<0.01). The anticonvulsant properties of the effective dose of lithium were prevented by pre-treatment with the per se non-effective doses of L-ARG [the substrate for nitric oxide synthase; NOS] (30 and 50 mg/kg) or sildenafil [a phosphodiesterase 5 inhibitor] (10 and 20 mg/kg). L-NAME [a non-specific NOS inhibitor] (5, 15 and 30 mg/kg), 7-NI [a specific neural NOS inhibitor] (30 and 60 mg/kg) or MB [a guanylyl cyclase inhibitor] (0.5 and 1 mg/kg) augmented the anticonvulsant effect of a sub-effective dose of lithium (10 mg/kg, i.p.). Whereas several doses of aminoguanidine [an inducible NOS inhibitor] (20, 50 and 100 mg/kg) failed to alter the anticonvulsant effect of lithium. Our findings demonstrated that nitric oxide-cyclic GMP pathway could be involved in the anticonvulsant properties of the lithium chloride. In addition, the role of constitutive NOS versus inducible NOS is prominent in this phenomenon.

Topics: Animals; Anticonvulsants; Arginine; Convulsants; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Indazoles; Injections, Intraperitoneal; Lithium Chloride; Male; Methylene Blue; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Pentylenetetrazole; Phosphodiesterase Inhibitors; Piperazines; Purines; Seizures; Sildenafil Citrate; Sulfones; Treatment Outcome

We have previously shown that kainic acid (KA) increases nitric oxide (NO) synthase (NOS) production in the rat dentate gyrus (DG) and hippocampus (CA3), and NOS inhibition [(by N(G)-nitro-L-arginine methylester (L-NAME)] modulates the vasoactive intestinal peptide (VIP)-responsive gene, activity-dependent neuroprotective protein, and alters neuro- and astrogliogenesis (Cosgrave et al. in Neurobiol Dis 30(3):281-292 2008, J Mol Neurosci 39(1-2):9-21, 2009, 2010). In the present study, using the same model we demonstrate that VIP synthesis is differentially regulated by the NO-cyclic guanosine monophosphate (cGMP) pathway in the DG and CA3 at 3 h and 3 days post-KA. At 3 h post-KA: In L-NAME+KA/7-nitroindazole (7-NI)+KA, stratum granulosum (SG) and subgranular zone (SGZ) cells were intensely stained for VIP when compared with L-NAME/7-NI/KA alone. Soluble guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, blocks cGMP production), suppressed astrocytic activation (glial fibrillary acidic protein) but other cell types were VIP(+); however, ODQ+KA suppressed overall VIP synthesis in the DG. At 3 days post-KA: In L-NAME+KA/7-NI+KA, SGZ and SG cells continued to express VIP, while in the KA alone, only SGZ cells were VIP(+). ODQ increased VIP(+) cells in the SG, and in contrast to 3 h, VIP-containing nNOS(+) cells increased in ODQ+KA when compared to vehicle+KA. In the hippocampus, 7-NI/ODQ had no effect on VIP at 3 h/3 days, while L-NAME+KA at 3 days increased VIP(+) cells, but reduced VIP-like immunoreactivity in astrocytes. These results suggest that the NO-cGMP pathway differentially regulates VIP in the DG and hippocampus during seizure.

Topics: Animals; Cyclic GMP; Dentate Gyrus; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Guanylate Cyclase; Hippocampus; Indazoles; Kainic Acid; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Oxadiazoles; Quinoxalines; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Soluble Guanylyl Cyclase; Vasoactive Intestinal Peptide

The aim of this work was to investigate in the avascular heart of the frog Rana esculenta the influence of nitric oxide (NO) on ventricular systolic and diastolic functions by using a novel image analysis technique. The external volume variations of the whole ventricle were monitored during the heart cycle by video acquisition(visible light) and analysed by an appropriately developed software with a specific formula for irregular convex solids. The system, which measures the rate of volume changes and the ejection fraction, directly determined the volumetric behaviour of the working frog heart after stimulation or inhibition of NOS-NOcGMP pathway. End-diastolic volume (EDVext), end-systolic volume (ESVext), contraction and relaxation velocities (dV/dtsys and dV/dtdia, respectively), stroke volume (SV) and ejection fraction (EF), were measured before and after perfusion with NOS substrate (L-arginine), NO donor (SIN-1), cGMP analogue (8-Br-cGMP),NOS inhibitors (NG-monomethyl-L-arginine, L-NMMA; L-N(5)-(1-iminoethyl)-ornithine, L-NIO; 7-Nitroindazole,7-NI) and guanylyl cyclase inhibitor (ODQ). The results showed that NO reduces ventricular systolicfunction improving diastolic filling, while NOS inhibition increases contractility impairing ventricular filling capacity. The presence of activated eNOS (p-eNOS) was morphologically documented, further supporting that the mechanical activity of the ventricular pump in frog is influenced by a tonic release of NOS-generated NO.

Topics: Animals; Anura; Arginine; Cyclic GMP; Female; Heart Ventricles; In Vitro Techniques; Indazoles; Male; Molsidomine; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; omega-N-Methylarginine; Perfusion; Serine; Software; Ventricular Function

The mechanism of action underlying the "analgesic activity" of diazepam remains unclear. In this study, the possible participation of the GABA/benzodiazepine receptor and the nitric oxide-cyclic GMP (NO-cGMP) pathway was assessed utilizing the pain-induced functional impairment model in the rat (PIFIR). Nociception was induced by an intra-articular injection of 15% uric acid. Diazepam (1 and 2 mg/kg, i.p.) reversed the dysfunction induced by uric acid. Flumazenil (10 mg/kg, i.p.), a GABA/benzodiazepine receptor antagonist, abolished the "antinociceptive-like effect" of diazepam (at 2 mg/kg). The "antinociceptive-like effect" of diazepam (at 2 mg/kg) was antagonized by the non-selective nitric oxide synthase (NOS) inhibitor, Nomega-L-nitro-arginine methyl ester hydrochloride (L-NAME, 5 mg/kg, s.c.) (but not by its inactive isomer), and by the selective neuronal NOS inhibitor, 7-nitroindazole (7-NI, 1 mg/kg, i.p). While, the NO precursor, l-arginine (125 mg/kg, s.c.), but not d-arginine (125 mg/kg, s.c.), increased the "antinociceptive-like effect" of a non-effective dose of diazepam (1 mg/kg). Methylene blue (10 mg/kg, i.p.), a guanylate cyclase inhibitor, also prevented the "antinociceptive-like effect" of diazepam (at 2 mg/kg). These results suggest that the GABA/benzodiazepine receptor and the NO-cGMP pathway participate in the "antinociceptive-like effect" of diazepam.

Topics: Analgesics; Animals; Arginine; Cyclic GMP; Diazepam; Enzyme Inhibitors; Guanylate Cyclase; Hypnotics and Sedatives; Indazoles; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase Type I; Pain Measurement; Rats; Rats, Wistar; Receptors, GABA-A; Signal Transduction

Antidepressant-like activity of folic acid in forced swimming test and in the tail suspension test was demonstrated previously by our group. In this study we investigated the involvement of N-methyl-d-aspartate (NMDA) receptors and l-arginine-nitric oxide (NO)-cyclic guanosine monophosphate pathway in its antidepressant-like effect in the forced swimming test in mice. The antidepressant-like effect of folic acid (10 nmol/site, i.c.v.) was prevented by the pretreatment of mice with NMDA (0.1 pmol/site, i.c.v.), l-arginine (750 mg/kg, i.p., substrate for nitric oxide synthase), S-nitroso-N-acetyl-penicillamine (SNAP, 25 microg/site, i.c.v, a NO donor) or sildenafil (5 mg/kg, i.p., phosphodiesterase 5 inhibitor). The administration of 7-nitroindazole (25 and 50 mg/kg, i.p., a specific neuronal nitric oxide synthase (nNOS) inhibitor) or methylene blue (20 mg/kg, i.p., direct inhibitor of both nitric oxide synthase and soluble guanylate cyclase) in combination with a sub-effective dose of folic acid (1 nmol/site, i.c.v.) reduced the immobility time in the FST as compared with either drug alone. Together the results suggest that the antidepressant-like effect of folic acid in the forced swimming test is dependent on an inhibition of either NMDA receptors or NO and cGMP synthesis.

Topics: Animals; Antidepressive Agents; Arginine; Cyclic GMP; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Female; Folic Acid; Indazoles; Injections, Intraventricular; Male; Methylene Blue; Mice; N-Methylaspartate; Nitric Oxide; Nitric Oxide Donors; Receptors, N-Methyl-D-Aspartate; S-Nitroso-N-Acetylpenicillamine; Signal Transduction; Swimming; Vitamin B Complex

It is known that several second messengers, such as Ca(2+) or cAMP, play important roles in the intracellular pathway of electrolyte secretion in tracheal submucosal gland. However, the participation of cGMP, and therefore nitric oxide (NO), is not well understood. To investigate the physiologic role of NO, we first examined whether tracheal glands can synthesize NO in response to acetylcholine (ACh), and then whether endogenous NO has some effects on the ACh-triggered ionic currents. From the experiments using the NO-specific fluorescent indicator 4,5-diaminofluorescein diacetate salt (DAF-2DA), we found that a physiologically relevant low dose of ACh (100 nM) stimulated the endogenous NO synthesis, and it was almost completely suppressed in the presence of the nonspecific NO synthase (NOS) inhibitor Nomega-Nitro-L-arginine Methyl Ester Hydrochloride (L-NAME) or the neuronal NOS (nNOS)-specific inhibitor 7-Nitroindazole (7-NI). Patch-clamp experiments revealed that both the NOS inhibitors (L-NAME or 7-NI) and cGK inhibitors (KT-5823 or Rp-8-Br-cGMP) partially decreased ionic currents induced by 30 nM of ACh, but not in the case of 300 nM of ACh. Our results indicate that NO can be synthesized through the activation of nNOS endogenously and has potentiating effects on the gland secretion, under a physiologically relevant ACh stimulation. When cells were stimulated by an inadequately potent dose of ACh, which caused an excess elevation in [Ca(2+)](i), the cells were desensitized. Therefore, due to NO, gland cells become more sensitive to calcium signaling and are able to maintain electrolyte secretion without desensitization.

Topics: Acetylcholine; Animals; Calcium Signaling; Carbazoles; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Enzyme Inhibitors; Exocrine Glands; In Vitro Techniques; Indazoles; Indoles; Models, Biological; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Protein Kinase Inhibitors; Sus scrofa; Trachea

Berberine is an isoquinoline alkaloid isolated from Berberis aristata, a major herb widely used in Indian and Chinese systems of medicine. Berberine possessed a wide range of biological activity including antidiarrheal, antimicrobial, anti-inflammatory effects and some central nervous system activity as well. The present study was designed to explore the antidepressant activity and its possible mechanism of action. Further, the involvement of L-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signaling pathway in the antidepressant action of berberine chloride was investigated. The antidepressant activity was assessed in forced-swim and tail-suspension tests. Total immobility period was recorded during a six-min test. Berberine (5-20 mg/kg, i.p.) produced a reduction in immobility period in both the tests. When berberine (5 mg/kg, i.p.) was co-administered with other antidepressant drugs, it enhanced the anti-immobility effect of subeffective doses of imipramine (2 mg/kg, i.p.), desipramine (5 mg/kg, i.p.), tranylcypromine (4 mg/kg, i.p.), fluoxetine (5 mg/kg, i.p.), venlafaxine (2 mg/kg, i.p.) or bupropion (10 mg/kg, i.p.) in forced-swim test. However, berberine did not modify the effects of mianserine (32 mg/kg, i.p.) or trazodone (2 mg/kg, i.p.), the two atypical antidepressant drugs. The neurochemical analysis revealed that berberine (5 mg/kg, i.p.) increased the levels of norepinephrine, serotonin or dopamine in the mouse whole brain. The antidepressant-like effect of berberine (5 mg/kg, i.p.) in forced-swim test was prevented by pretreatment with L-arginine (750 mg/kg, i.p.) [substrate for nitric oxide synthase (NOS)]. Pretreatment of mice with 7-nitroindazole (25 mg/kg, i.p.) [a specific neuronal nitric oxide synthase (nNOS) inhibitor] produced potentiation of the action of subeffective dose of berberine (2 mg/kg, i.p.). In addition, treatment of mice with methylene blue (10 mg/kg, i.p.) [direct inhibitor of both nitric oxide synthase (NOS) and soluble guanylate cyclase (sGC)] potentiated the effect of berberine (2 mg/kg, i.p.) in the forced-swim test. Furthermore, the reduction in the immobility period elicited by berberine (5 mg/kg, i.p.) was also inhibited by pretreatment with sildenafil (5 mg/kg, i.p.) [phosphodiesterase 5 inhibitor]. The various modulators and their combination with berberine did not produce any changes in locomotor activity. Our findings demonstrated that berberine exerted antidepressant-like effect in various

Topics: Animals; Antidepressive Agents; Arginine; Behavior, Animal; Berberine; Brain Chemistry; Cyclic GMP; Dose-Response Relationship, Drug; Drug Synergism; Hindlimb Suspension; Indazoles; Injections, Intraperitoneal; Male; Mice; Motor Activity; Neurotransmitter Agents; Nitric Oxide; Piperazines; Purines; Signal Transduction; Sildenafil Citrate; Stress, Psychological; Sulfones; Swimming; Time Factors

Catalepsy is a preclinical test that predicts extrapyramidal symptoms in humans. It models symptoms of acute extrapyramidal side effects induced at the beginning of antipsychotic treatment. Nitric oxide (NO) plays a role in a series of neurobiological functions underlying behavior. For example, inhibition of NO synthesis disrupts rodent exploratory behavior and induces catalepsy. Although several effects mediated by NO involve the activation of soluble guanylyl cyclase (sGC), the transduction mechanism of the catalepsy-inducing effect of NO has not yet been investigated.. The study was designed to test if intracerebroventricular (i.c.v.) microinjection of NO-sensitive inhibitors of sGC (NO-sGC) induces catalepsy in mice similar to that induced by NO synthase (NOS) inhibitors. Exploratory behavior was tested in the open field. In addition, the effects of a NOS inhibitor on oxidative metabolites of NO were measured in the striatum.. Drug effects were examined in the hanging-bar test after the following i.c.v. treatments: oxadiazolo-quinoxalin (ODQ, 30-300 nmol) or methylene blue (MB, 3-100 nmol), selective and nonselective sGC inhibitors, respectively, or 7-nitroindazole (7-NI, 3-90 nmol) and G-nitro-L: -arginine methyl ester (L: -NAME, 3-90 nmol), selective and nonselective neuronal NOS inhibitors. To test if the effects were related to interference with the NO system, additional groups received 7-NI (30 nmol), ODQ (100 nmol), or L-NAME (90 nmol) preceded by L: -arginine (L: -arg, 30-100 nmol, i.c.v. 30 min before). A possible interference of ODQ and 7-NI on exploratory behavior was tested in an open field. The concentration of nitrites and nitrates (NO( x )) in striatum homogenates was measured by the Griess reaction.. Both NO-sGC and NOS inhibitors induced catalepsy in mice that lasted for at least 2 h. The range of effective doses of these drugs, however, was limited, and the dose-effect curves had an inverted U shape. The cataleptic effect induced by L: -NAME was inversely correlated with NO( x ) products in the striatum. The cataleptic effect of 7-NI and ODQ was prevented by pretreatment with L: -arginine. No drug changed exploratory behavior in the open field.. This study showed that pharmacological disruption of the endogenous NO-sGC signaling in the central nervous system induces long-lasting catalepsy in mice. Moreover, the cataleptic effect of NOS inhibition correlates with the decrease in NO( x ) products formation in the striatum. The results give further support to the hypothesis that NO plays a role in motor behavior control mediated, at least in part, by cyclic guanosine monophosphate production in the striatum.

Topics: Animals; Arginine; Behavior, Animal; Catalepsy; Corpus Striatum; Cyclic GMP; Dose-Response Relationship, Drug; Enzyme Inhibitors; Guanylate Cyclase; Indazoles; Injections, Intraventricular; Male; Methylene Blue; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Oxadiazoles; Quinoxalines; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Soluble Guanylyl Cyclase; Time Factors

Conflicting results have been reported regarding the role of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway in the hippocampus on anxiety modulation.. To investigate the effects of intrahippocampal injections of drugs that modify the NO-cGMP pathway in rats submitted to two animal models that are sensitive to anxiolytic drugs, the elevated plus-maze and the Vogel punished licking test.. Male Wistar rats with cannulae aimed at the dentate gyrus of the dorsal hippocampus received microinjections of the NO synthase (NOS) inhibitors N (G)-nitro-L: -arginine methyl ester (LNAME, 15-300 nmol/0.2 microl), N (G)-nitro-L: -arginine (LNOARG, 50-300 nmol/0.2 microl), 7-nitroindazole (7NI, 10-100 nmol/0.2 microl), or the soluble guanylate cyclase inhibitor 1H-oxadiazolo-quinoxalin-1 one (ODQ, 10-100 nmol/0.2 microl), and were submitted to the elevated plus-maze. In a second group, the animals received 7NI, LNAME, or ODQ and were submitted to the Vogel punished licking test. To control for drug-induced changes in locomotor behavior, the animals were submitted to an open arena or to the Rota-rod test.. All drugs increased the exploration of the open arms of the elevated plus-maze. They also increased the number of punished licks in the Vogel test, indicating an anxiolytic effect. The anxiolytic effect of LNAME was prevented by previous treatment with L: -arginine (300 nmol/0.2 microl). Except for the lower dose of LNAME (15 nmol), administration of the NOS inhibitors or ODQ did not change exploratory activity in the open field nor cause any gross locomotor impairment in the Rota-rod test.. The results suggest that NO plays an anxiogenic role in the dentate gyrus of the dorsal hippocampus.

Topics: Analysis of Variance; Animals; Anxiety; Cyclic GMP; Dentate Gyrus; Dose-Response Relationship, Drug; Guanylate Cyclase; Hippocampus; Indazoles; Male; Maze Learning; Microinjections; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxadiazoles; Punishment; Quinoxalines; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Soluble Guanylyl Cyclase

The possible participation of the nitric oxide (NO)-cyclic GMP-protein kinase G (PKG) pathway on gabapentin-induced spinal antiallodynic activity was assessed in spinal nerve injured rats. Intrathecal gabapentin, diazoxide or pinacidil reduced tactile allodynia in a dose-dependent manner. Pretreatment with NG-L-nitro-arginine methyl ester (L-NAME, non-specific inhibitor of NO synthase NOS), 7-nitroindazole (neuronal NO synthase inhibitor), 1H-[1,2,4] -oxadiazolo [4,3-a] quinoxalin-1-one (ODQ, guanylyl cyclase inhibitor) or (9S, 10R, 12R)-2,3,9,10,11,12-hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9,12-epoxy-1H-diindolo-[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT-5823, specific PKG inhibitor), but not NG-D-nitro-arginine methyl ester (D-NAME) or okadaic acid (protein phosphatase 1 and 2 inhibitor) prevented gabapentin-induced antiallodynia. Pinacidil activity was not blocked by L-NAME, D-NAME, 7-nitroindazole, ODQ, KT-5823 or okadaic acid. Moreover, KT-5823, glibenclamide (ATP-sensitive K+ channel blocker), apamin and charybdotoxin (small- and large-conductance Ca2+-activated K+ channel blockers, respectively), but not margatoxin (voltage-gated K+ channel blocker), L-NAME, 7-nitroindazole, ODQ or okadaic acid, reduced diazoxide-induced antiallodynia. Data suggest that gabapentin-induced spinal antiallodynia could be due to activation of the NO-cyclic GMP-PKG-K+ channel pathway.

Topics: Amines; Analgesics; Animals; Apamin; Carbazoles; Charybdotoxin; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cyclohexanecarboxylic Acids; Diazoxide; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Gabapentin; gamma-Aminobutyric Acid; Glyburide; Indazoles; Indoles; Injections, Spinal; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Okadaic Acid; Oxadiazoles; Pain; Pinacidil; Potassium Channel Blockers; Potassium Channels; Protein Kinase Inhibitors; Quinoxalines; Rats; Rats, Wistar; Signal Transduction; Spinal Nerves; Stereoisomerism; Time Factors; Vasodilator Agents

The study was aimed at investigating the expression and the activity of neuronal nitric oxide synthase, and of soluble guanylyl cyclase and phosphodiesterase activities that regulate guanosine 3',5'-cyclic monophosphate level in the midbrain, in a mouse model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injections. Adult male mice of the C57/BL strain were given three i.p. injections of physiological saline or three i.p. injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine solution in physiological saline at 2 h intervals (summary 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine dose: 40 mg/kg), and were killed 3, 7, or 14 days later. mRNA, protein level, and/or activities of neuronal nitric oxide synthase, soluble guanylyl cyclase, phosphodiesterase and guanosine 3',5'-cyclic monophosphate were determined. Immunohistochemistry showed about 75% decrease in the number of tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine showed increased midbrain guanylyl cyclase and total nitric oxide synthase activities at 3, 7, and 14 days post-treatment. The specific neuronal nitric oxide synthase inhibitor 7-nitroindazole (10 microM) and the specific inducible nitric oxide synthase inhibitor 1400W (10 microM) inhibited the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced excess in nitric oxide synthase activity by 63-70 and 13-25%, respectively. The increases in total midbrain nitric oxide synthase activity were accompanied by elevated guanosine 3',5'-cyclic monophosphate, enhanced expression of neuronal nitric oxide synthase and of the beta1 subunit of guanylyl cyclase at both mRNA and protein levels that persisted up to the end of the observation period, and by enhanced neuronal nitric oxide synthase and guanylyl cyclase beta1 immunoreactivities in substantia nigra pars compacta 7 and 14 days after the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment. The increases in guanylyl cyclase activity were found to occur exclusively due to increased maximal enzyme activity. No 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced change in phosphodiesterase activity has been detected in any brain region studied. 7-Nitroindazole prevented a significant increase in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced midbrain guanosine 3',5'-cyclic monophosphate level and neurodegeneration of dopaminergic neurons. These results raise the possibility that the nitric

Topics: 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; Analysis of Variance; Animals; Cell Count; Cyclic GMP; Disease Models, Animal; Drug Administration Schedule; Gene Expression Regulation; Guanylate Cyclase; Immunohistochemistry; Indazoles; Male; Mesencephalon; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Parkinsonian Disorders; Time Factors; Tyrosine 3-Monooxygenase

Post-traumatic stress disorder (PTSD) may be associated with shrinkage of the hippocampus, with glutamate release causally related to these events. Recent animal studies strongly implicate activation of the nitric oxide (NO)-cascade in anxiety and stress. Using an animal model of repeated trauma, the effect of stress was investigated on the hippocampal NO-cGMP signalling pathway, specifically the release of nitrogen oxides (NOx) and its modulation by NMDA receptor-, NO-, cGMP- and nuclear factor K-beta (NFK-beta)-selective drugs. Immediately after stress, rats received the glutamate NMDA receptor antagonist, memantine (MEM; 5 mg/kg i.p./d), the NO synthase inhibitor, 7-nitroindazole sodium salt (7-NINA; 20 mg/kg i.p./d), the cGMP-specific PDE inhibitor, sildenafil (SIL; 10 mg/kg i.p./d) or the NFkappa-beta antagonist, pyrollidine dithiocarbamate (PDTC; 70 mg/kg i.p./d), for 7 days. Stress significantly increased hippocampal NOx on day 7 post-stress, which was blocked by either 7-NINA or PDTC, while MEM was without effect. SIL, however, significantly augmented stress-induced NOx accumulation. Increased cGMP therefore acts as a protagonist in driving stress-related events, while both nNOS (neuronal NOS) and iNOS (inducible/immunological NOS) may represent a therapeutic target in preventing the effects of severe stress. The value of NMDA receptor antagonism, however, appears limited in this model.

Topics: Animals; Cyclic GMP; Disease Models, Animal; Hippocampus; Indazoles; Male; NF-kappa B; Nitric Oxide; Piperazines; Proline; Purines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Sildenafil Citrate; Stress Disorders, Post-Traumatic; Sulfones; Thiocarbamates

The ability of endothelins 1 and 3 (ET-1 and ET-3) to reduce neuronal norepinephrine release through ETB receptor activation involving nitric oxide (NO) pathways in the rat anterior hypothalamus region (AHR) was previously reported. In the present work, we studied the effects of ET-1 and -3 on tyrosine hydroxylase (TH) activity and the possible involvement of NO pathways. Results showed that ET-1 and -3 (10 nM) diminished TH activity in AHR and this effect was blocked by a selective ETB receptor antagonist (100 nM BQ-788), but not by a ET(A) receptor antagonist (BQ-610). To confirm these results, 1 microM IRL-1620 (ET(B) agonist) reduced TH activity whereas 300 nM sarafotoxin S6b falled to modify it. N(omega)-Nitro-L-arginine methyl ester (10 microM), 7-nitroindazole (10 microM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-ona (10 microM), KT5823 (2 microM), inhibitors of nitric oxide synthase, neuronal nitric oxide synthase, NO-sensitive-guanylyl cyclase, and protein kinase G, respectively, did not modify the reduction of TH activity produced by ETs. In addition, both 100 microM sodium nitroprusside and 50 microM 8-bromoguanosine-3',5'-cyclic monophosphate (NO donor and guanosine-3',5'-cyclic monophosphate analog, respectively) diminished TH activity. Present results showed that ET-1 and ET-3 diminished TH activity through the activation of ET(B) receptors involving the NO/guanosine-3',5'-cyclic monophosphate/protein kinase G pathway. Taken jointly present and previous results it can be concluded that both ETs play an important role as modulators of norepinephrine neurotransmission in the rat AHR.

Topics: Animals; Carbazoles; Cyclic GMP; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Endothelin-3; Hypothalamus, Anterior; Indazoles; Indoles; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase Type I; Nitroprusside; Oligopeptides; Oxadiazoles; Piperidines; Quinoxalines; Rats; Suramin; Tyrosine 3-Monooxygenase

Several regulated Ca2+ entry pathways have been identified, with capacitative Ca2+ entry (CCE) being the most characterized. In the present study, we examined Ca2+ entry pathways regulated by arachidonic acid (AA) in mouse parotid acini. AA induced Ca2+ release from intracellular stores, and increased Ca2+ entry. AA inhibited thapsigargin (Tg)-induced CCE, whereas AA activated Ca2+ entry when CCE was blocked by gadolinium (Gd3+). AA-induced Ca2+ entry was associated with depletion of calcium from ryanodine-sensitive stores; both AA-induced Ca2+ release and Ca2+ entry were inhibited by tetracaine and the nitric oxide synthase (NOS) inhibitor, 7-nitroindazole (7-NI). The nitric oxide (NO) donor, 1,2,3,4-ox-triazolium,5-amino-3-(3,4-dichlorophenyl)-chloride (GEA 3162), but not 8-bromo-cGMP, mimicked the effects of AA in inhibiting CCE. Results suggest that AA acts via nitric acid to inhibit the CCE pathway that is selective for Ca2+, and to activate a second Ca2+ entry pathway that is dependent on depletion of Ca2+ from ryanodine-sensitive stores.

Topics: Animals; Arachidonic Acid; Calcium; Calcium Signaling; Cells, Cultured; Cyclic GMP; Enzyme Inhibitors; Fura-2; Gadolinium; Indazoles; Mice; Nitric Oxide; Parotid Gland; Ryanodine; Tetracaine; Thapsigargin; Triazoles

We measured changes in nitric oxide (NO) concentration in the cerebral cortex during experimental carbon monoxide (CO) poisoning and assessed the role for N-methyl-d-aspartate receptors (NMDARs), a glutamate receptor subtype, with progression of CO-mediated oxidative stress. Using microelectrodes, NO concentration was found to nearly double to 280 nM due to CO exposure, and elevations in cerebral blood flow, monitored as laser Doppler flow (LDF), were found to loosely correlate with NO concentration. Neuronal nitric oxide synthase (nNOS) activity was the cause of the NO elevation based on the effects of specific NOS inhibitors and observations in nNOS knockout mice. Activation of nNOS was inhibited by the NMDARs inhibitor, MK 801, and by the calcium channel blocker, nimodipine, thus demonstrating a link to excitatory amino acids. Cortical cyclic GMP concentration was increased due to CO poisoning and shown to be related to NO, versus CO, mediated guanylate cyclase activation. Elevations of NO were inhibited when rats were infused with superoxide dismutase and in rats depleted of platelets or neutrophils. When injected with MK 801 or 7-nitroindazole, a selective nNOS inhibitor, rats did not exhibit CO-mediated nitrotyrosine formation, myeloperoxidase (MPO) elevation (indicative of neutrophil sequestration), or impaired learning. Similarly, whereas CO-poisoned wild-type mice exhibited elevations in nitrotyrosine and myeloperoxidase, these changes did not occur in nNOS knockout mice. We conclude that CO exposure initiates perivascular processes including oxidative stress that triggers activation of NMDA neuronal nNOS, and these events are necessary for the progression of CO-mediated neuropathology.

Topics: Animals; Brain Chemistry; Calcium Channel Blockers; Carbon Monoxide Poisoning; Cyclic GMP; Dizocilpine Maleate; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Indazoles; Laser-Doppler Flowmetry; Male; Maze Learning; Mice; Mice, Knockout; Microelectrodes; Neurons; Neurotoxicity Syndromes; Neutropenia; Neutrophils; NG-Nitroarginine Methyl Ester; Nimodipine; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Platelet Count; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Tyrosine

The aim was to determine the effect of acute and chronic administration of 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, on the righting reflex ED50 and the minimum alveolar concentration during sevoflurane anaesthesia in rats.. 7-Nitroindazole was acutely (0, 50 and 100 mg kg(-1)) and chronically (0 and 150 mg kg(-1) day(-1), 4 days) administered to rats. After the preparation, the minimum alveolar concentration and the righting reflex ED50 were measured. The concentration of cGMP in the brain, cerebellum and spinal cord was also measured.. Acute administration reduced the minimum alveolar concentration (50 mg kg(-1), 58.8% (95% CI: 50.3-67.3%) of the baseline value, P < 0.01; 100 mg kg(-1), 55.8 (46.9-64.7), P < 0.01) and the righting reflex ED50 (50 mg kg(-1), 27.2 (17.2-37.2), P < 0.01; 100 mg kg(-1), 14.3 (6.6-22.0), P < 0.01). Chronic administration did not reduce the minimum alveolar concentration; however, it reduced the righting reflex ED50 (65.3 (52.9-77.7), P < 0.01). Overall, the reduction in minimum alveolar concentration in the acute and chronic protocol did not correlate with that of the righting reflex ED50. 7-Nitroindazole (100 mg kg(-1), acute) reduced the cGMP concentration within the cerebellum by 55.4%; however, it did not decrease concentrations in the brain or spinal cord.. Different mechanisms are responsible for the observed alterations to the minimum alveolar concentration and the righting reflex ED50 following treatment with 7-nitroindazole. The nitric oxide-cGMP pathway might play a less important role in the determination of minimum alveolar concentration than the righting reflex ED50.

Topics: Anesthetics, Inhalation; Animals; Blood Gas Analysis; Brain; Cerebellum; Cyclic GMP; Drug Interactions; Enzyme Inhibitors; Indazoles; Male; Methyl Ethers; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Postural Balance; Pulmonary Alveoli; Rats; Rats, Sprague-Dawley; Sevoflurane; Spinal Cord

The effect of L-arginine on the slow motility of mammalian cochlear outer hair cells was studied in this experiment. L-Arginine (3 mM) but not D-arginine (3 mM) or other amino acids (L-aspartate or L-glutamate) induced length increases of guinea pig outer hair cell. Similarly, the membrane-permeant cGMP analogues, 8-(4-chlorophenylthio)guanosine 3':5'-cyclic monophosphate (1 mM) or 8-bromo-guanosine 3':5'-cyclic monophosphate (1 mM) induced length increases of guinea pig outer hair cells. These length increases induced by L-arginine can be attenuated by a 30 min preincubation of the cells with the nitric oxide synthase inhibitors N(G)-nitro-L-arginine methyl ester hydrochloride (3 mM) or 7-nitroindazole (1 mM). Comparing the effects of L-arginine and ionomycin on cell length and intracellular calcium change in outer hair cells, both L-arginine and ionomycin were able to induce the elongation of outer hair cells but L-arginine did not change the fluorescence intensity of Fluo-3. Preincubation of the cells with EGTA (3 mM) for 40 min to reduce the extracellular calcium concentration did not influence the effect of L-arginine. This experiment demonstrated that nitric oxide/cGMP pathway involvement in regulating the slow motility of mammalian outer hair cells cannot be ruled out. The effect of L-arginine is independent of extracellular calcium concentration.

Topics: Animals; Arginine; Calcium; Cell Membrane Permeability; Cell Movement; Cell Size; Cyclic GMP; Enzyme Inhibitors; Extracellular Fluid; Guinea Pigs; Hair Cells, Auditory, Outer; Indazoles; Intracellular Membranes; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Osmolar Concentration

Endogenous opioids and nitric oxide (NO) are recognized modulators of cardiac function. Enkephalins and inhibitors of NO synthase (NOS) both produce similar interruptions in the vagal control of heart rate. This study was conducted to test the hypothesis that NO systems within the canine sinoatrial (SA) node facilitate local vagal transmission and that the endogenous enkephalin methionine-enkephalin-arginine-phenylalanine (MEAP) attenuates vagal bradycardia by interrupting the NOS-cGMP pathway. Microdialysis probes were inserted into the SA node, and they were perfused with nonselective (Nomega-nitro-l-arginine methyl ester) and neuronal (7-nitroindazole) NOS inhibitors. The right vagus nerve was stimulated and both inhibitors gradually attenuated the resulting vagal bradycardia. The specificity of these inhibitions was verified by an equally gradual reversal of the inhibition with an excess of the NOS substrate l-arginine. Introduction of MEAP into the nodal interstitium produced a quickly developing but quantitatively similar interruption of vagal bradycardia that was also slowly reversed by the addition of l-arginine and not by d-arginine. Additional support for convergence of opioid and NO pathways was provided when the vagolytic effects of MEAP were also reversed by the addition of the NO donor S-nitroso-N-acetyl-penicillamine, the protein kinase G activator 8-bromo-cGMP, or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. MEAP and 7-nitroindazole were individually combined with the direct acting muscarinic agonist methacholine to evaluate potential interactions with muscarinic receptors within the SA node. MEAP and 7-nitroindazole were unable to overcome the bradycardia produced by methacholine. These data suggest that NO and enkephalins moderate the vagal control of heart rate via interaction with converging systems that involve the regulation of cAMP within nodal parasympathetic nerve terminals.

Topics: 1-Methyl-3-isobutylxanthine; Animals; Arginine; Bradycardia; Cyclic GMP; Dogs; Dose-Response Relationship, Drug; Enkephalin, Methionine; Enzyme Inhibitors; Indazoles; Methacholine Chloride; NG-Nitroarginine Methyl Ester; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Parasympathomimetics; Penicillamine; Phosphodiesterase Inhibitors; Sinoatrial Node; Vagus Nerve

1. A possible role of nitric oxide (NO) as a modulator of capsaicin-sensitive sensory neurotransmission in blood vessels was investigated in the rat isolated mesenteric arterial bed. 2. Electrical field stimulation (EFS) of methoxamine-preconstricted mesenteric beds elicited frequency-dependent vasorelaxation mediated by capsaicin-sensitive sensory nerves. N(G)-nitro-L-arginine methyl ester (L-NAME, 10 and 300 microM) and 7-nitroindazole (7-NI, 100 microM), inhibitors of nitric oxide synthase (NOS), augmented sensory neurogenic vasorelaxation. D-NAME (300 microM), 6-aminoindazole (100 microM) and N(omega)-propyl-L-arginine (50 nM), a selective inhibitor of neuronal NOS, were without effect. The effect of 10 microM L-NAME was reversed by L-arginine (1 mM), the substrate for NOS. 3. L-NAME (300 microM) and 7-NI (100 microM) had no significant effect on vasorelaxations to calcitonin gene-related peptide (CGRP), the principal motor neurotransmitter of capsaicin-sensitive sensory nerves in rat mesenteric arteries, or to capsaicin, indicating a prejunctional action. The inhibitors of NOS had no effect on vasorelaxation to forskolin, but augmented vasorelaxation to sodium nitroprusside (SNP). 4. Removal of the endothelium augmented sensory neurogenic vasorelaxation, but did not affect vasorelaxation to CGRP, indicating a prejunctional action of endothelial NO. 5. In the absence of endothelium, L-NAME (300 microM) inhibited, and 7-NI (100 microM) caused no further augmentation of sensory neurotransmission. 6. SNP (100 nM), a nitric oxide donor, attenuated sensory neurogenic relaxations to EFS. 7. In rat isolated thoracic aortic rings, L-NAME (100 microM) and 7-NI (100 microM) attenuated concentration-dependent relaxations to acetylcholine. 8. These data show that NO modulates sensory neurotransmission evoked by EFS of the rat isolated mesenteric arterial bed, and that when NO synthesis is blocked sensory neurogenic relaxation is augmented. The source of NO is the vascular endothelium.

Topics: Animals; Arginine; Bucladesine; Calcitonin Gene-Related Peptide; Capsaicin; Cyclic GMP; Electric Stimulation; Endothelium, Vascular; In Vitro Techniques; Indazoles; Male; Mesenteric Arteries; Neurons, Afferent; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitroprusside; Rats; Rats, Wistar; Vasodilation; Vasodilator Agents

The forced swimming test (FST) has been extensively used as a screening model for new antidepressant agents. It has been shown that drugs which reduce the amount of nitric oxide (NO) have the same outcome in this model as classic antidepressants. In addition, previous studies have shown that methylene blue, which acts as a direct inhibitor of both NOS and soluble guanylate cyclase (sGC), mimics the effect of clinically effective antidepressants in patients and in the FST. The present study examined the effects of the specific inhibitor of the NO-sGC pathway, [1H-[1,2,4]Oxadiazole[4,3-a]quinoxalin-1-one] (ODQ) and of the neuronal NOS inhibitor 7-nitroindazole (7-NI) in the FST. We found that ODQ (10 and 20 mg/kg) significantly decreased the immobility time in the FST compared to the control. Similarly, injections of 7-NI (30 or 60 mg/kg) reduced immobility time as well as Imipramine (IMI, 30 mg/kg). Interestingly, L-Arginine (250 mg/kg) administered in combination with ODQ reversed the effect of ODQ but displayed no effect when administered alone. Locomotion activity was significantly decreased following administration of IMI (30 mg/kg) and 7-NI (30 and 60 mg/kg) but was unaffected after administration of ODQ (10 and 20 mg/kg). These findings suggest that the NO-sGC-cGMP pathway may play an important role in the mediation of the behavioural effect in the FST without influence on motor activity.

Topics: Animals; Antidepressive Agents, Tricyclic; Arginine; Cyclic GMP; Depression; Dimethyl Sulfoxide; Enzyme Inhibitors; Guanylate Cyclase; Imipramine; Indazoles; Male; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Oxadiazoles; Quinoxalines; Rats; Rats, Sprague-Dawley; Swimming

We hypothesize that inhibitory effects exist between prostanoids and nitric oxide (NO) in their contributions to cerebral circulation. Piglets (1-4 days old) were divided into three chronically treated (6-8 days) groups: control piglets, piglets treated with indomethacin (75 mg/day), and piglets treated with N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 mg x kg(-1) x day(-1)). Pial arterioles dilated in response to hypercapnia similarly among the three groups (41 +/- 4, 40 +/- 6, and 45 +/- 11%). Cerebrospinal fluid cAMP increased in control piglets, while cGMP increased in indomethacin-treated piglets. L-NAME, but not 7-nitroindazole, inhibited the response to hypercapnia only in indomethacin-treated piglets (40 +/- 6 vs. 17 +/- 5%). Topical sodium nitroprusside or iloprost restored dilation in response to hypercapnia. Similar results were obtained when the dilator was bradykinin. Pial arterioles of control and L-NAME-treated piglets constricted in response to ACh (-24 +/- 3%). However, those of indomethacin-treated piglets dilated in response to ACh (15 +/- 2%). This dilation was inhibited by L-NAME. NO synthase activity, but not endothelial NO synthase expression, increased after chronic indomethacin treatment. These data suggest that chronic inhibition of cyclooxygenase can increase the contribution of NO to cerebrovascular circulatory control in piglets.

Topics: Acetylcholine; Animals; Animals, Newborn; Bradykinin; Cardiovascular Agents; Cells, Cultured; Cerebrovascular Circulation; Cyclic AMP; Cyclic GMP; Cyclooxygenase Inhibitors; Endothelium, Vascular; Enzyme Inhibitors; Hypercapnia; Indazoles; Indomethacin; Microcirculation; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Pia Mater; Swine; Vasodilator Agents

We examined modulation by nitric oxide (NO) of sympathetic neurotransmitter release and vasoconstriction in the isolated pump-perfused rat kidney. Electrical renal nerve stimulation (RNS; 1 and 2 Hz) increased renal perfusion pressure and renal norepinephrine (NE) efflux. Nonselective NO synthase (NOS) inhibitors [N(omega)-nitro-L-arginine methyl ester (L-NAME) or N(omega)-nitro-L-arginine], but not a selective neuronal NO synthase inhibitor (7-nitroindazole sodium salt), suppressed the NE efflux response and enhanced the perfusion pressure response. Pretreatment with L-arginine prevented the effects of L-NAME on the RNS-induced responses. 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), which eliminates NO by oxidizing it to NO(2), suppressed the NE efflux response, whereas the perfusion pressure response was less susceptible to carboxy-PTIO. 8-Bromoguanosine cGMP suppressed and a guanylate cyclase inhibitor [4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one] enhanced the RNS-induced perfusion pressure response, but neither of these drugs affected the NE efflux response. These results suggest that endogenous NO facilitates the NE release through cGMP-independent mechanisms, NO metabolites formed after NO(2) rather than NO itself counteract the vasoconstriction, and neuronal NOS does not contribute to these modulatory mechanisms in the sympathetic nervous system of the rat kidney.

Topics: Animals; Benzoates; Cyclic GMP; Electric Stimulation; Enzyme Inhibitors; Imidazoles; In Vitro Techniques; Indazoles; Kidney; Male; Nervous System; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitroarginine; Norepinephrine; Oxadiazoles; Oxazines; Perfusion; Pressure; Rats; Rats, Wistar

Systemic inhibition of nitric oxide synthase (NOS) in streptozotocin-induced (STZ-induced) diabetic rats results in decreases in glomerular filtration rate (GFR) and renal plasma flow (RPF) and an increase in renal vascular resistance (RVR). However, the exact isoform of NOS involved in diabetic renal hyperfiltration has not been determined. This study was conducted to clarify whether NO derived from neuronal NOS is involved in diabetic renal hyperfiltration when using a selective inhibitor of neuronal NOS, 7-nitro indazole (7-NI). Continuous infusion of NG-nitro-L -arginine methyl ester (L-NAME) at 5 microg/kg/min ameliorated renal hyperfiltration, decreased RPF, and increased RVR in diabetic rats without affecting the mean arterial pressure (MAP). 7-NI administered intraperitoneally in diabetic rats significantly reduced GFR without affecting MAP, but the renal hyperfiltration was still observed after the administration of 7-NI. The combined administration of L-NAME after 7-NI caused a further decrease in GFR in diabetic rats and ultimately resulted in normalization of GFR. 7-NI did not change any parameters of renal hemodynamics in control rats. Urinary excretion of nitrite/nitrate and cyclic guanosine monophosphate was significantly increased in diabetic rats over values found in control rats. Our results suggested that a local inhibition of NO in the kidney was involved in the amelioration of diabetic renal hyperfiltration and that NO derived from neuronal NOS is involved, at least in part, in renal hyperfiltration in STZ-induced diabetic rats.

Topics: Animals; Cyclic GMP; Diabetes Mellitus, Experimental; Drug Synergism; Enzyme Inhibitors; Glomerular Filtration Rate; Hemodynamics; Indazoles; Infusions, Intravenous; Injections, Intraperitoneal; Male; NG-Nitroarginine Methyl Ester; Nitrates; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitrites; Rats; Rats, Sprague-Dawley; Renal Plasma Flow; Vascular Resistance

Nitric oxide (NO) is synthesized from L-arginine by NO synthase (NOS). NO stimulates the soluble form of guanylyl cyclase (sGC) and induces accumulation of cyclic guanosine monophosphate (cGMP). The purpose of this study was to examine whether the cardiovascular responses induced by N-methyl-D-aspartate (NMDA) in the rostral ventrolateral medulla (RVLM) depend on the actions of NOS and sGC. In anesthetized cats, the extracellular NO level was measured by in vivo voltammetry using a nafion/porphyrine/o-phenylenediamine-coated carbon-fiber electrode. Microinjection of NMDA into the RVLM produced hypertension and bradycardia associated with NO formation. These NMDA-induced responses were attenuated by prior injections of 7-nitroindazole, a neuronal NO synthase (nNOS) inhibitor, and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a sGC inhibitor. These findings suggest that NO is involved in the NMDA-induced cardiovascular responses in the RVLM.

Topics: Animals; Blood Pressure; Bradycardia; Cats; Cyclic GMP; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Female; Guanylate Cyclase; Heart Rate; Hypertension; Indazoles; Male; Medulla Oblongata; N-Methylaspartate; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Oxadiazoles; Quinoxalines; Receptors, N-Methyl-D-Aspartate; Signal Transduction

In this study, we investigated the involvement of the interaction between sigma receptors and the nitric oxide/cyclic GMP pathway in short term memory in mice, assessed through spontaneous alternation behavior in a Y-maze. N(G)-Nitro-L-arginine methyl ester and 7-nitro indazole, both nitric oxide synthase inhibitors, impaired the spontaneous alternation behavior. These impairments were attenuated by (+) SKF 10,047 and (+) pentazocine, sigma(1) receptor agonists. Further, the sigma(1) receptor antagonist, NE-100, reversed the improvements made by sigma receptor agonists. Cyclic GMP levels and nitric oxide synthase activity in the hippocampus were reduced by treatment with N(G)-nitro-L-arginine methyl ester. The suppressive effects of N(G)-nitro-L-arginine methyl ester on the cyclic GMP levels were reversed by co-treatment with (+) SKF 10,047, but the decline in nitric oxide synthase activity was not. These results suggest that the nitric oxide/cyclic GMP pathway in the hippocampus is responsible for spontaneous alternation behavior in a Y-maze. Further, the ameliorating effects of (+) SKF 10,047 on the impairment of spontaneous alternation behavior may be mediated through activation of guanylate cyclase, but not nitric oxide synthase in the hippocampus of mice.

Topics: Analgesics, Opioid; Animals; Anti-Anxiety Agents; Antipsychotic Agents; Behavior, Animal; Brain Chemistry; Cyclic GMP; Enzyme Inhibitors; Guanidines; Indazoles; Male; Methylene Blue; Mice; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Pentazocine; Phenazocine; Pyrimidines; Receptors, sigma

The grasshopper embryo has been used as a convenient system with which to investigate mechanisms of axonal navigation and pathway formation at the level of individual nerve cells. Here, we focus on the developing antenna of the grasshopper embryo (Schistocerca gregaria) where two siblings of pioneer neurons establish the first two axonal pathways to the CNS. Using immunocytochemistry we detected nitric oxide (NO)-induced synthesis of cGMP in the pioneer neurons of the embryonic antenna. A potential source of NO are NADPH-diaphorase-stained epithelial cells close to the basal lamina. To investigate the role of the NO/cGMP signaling system during pathfinding, we examined the pattern of outgrowing pioneer neurons in embryo culture. Pharmacological inhibition of soluble guanylyl cyclase (sGC) and of NO synthase (NOS) resulted in an abnormal pattern of pathway formation in the antenna. Axonogenesis of both pairs of pioneers was inhibited when specific NOS or sGC inhibitors were added to the culture medium; the observed effects include the loss axon emergence as well as retardation of outgrowth, such that growth cones do not reach the CNS. The addition of membrane-permeant cGMP or a direct activator of the sGC enzyme to the culture medium completely rescued the phenotype resulting from the block of NO/cGMP signaling. These results indicate that NO/cGMP signaling is involved in axonal elongation of pioneer neurons in the antenna of the grasshopper.

Topics: Animals; Axonal Transport; Axons; Cyclic GMP; Dihydrolipoamide Dehydrogenase; Embryo, Nonmammalian; Enzyme Inhibitors; Grasshoppers; Guanylate Cyclase; Horseradish Peroxidase; Indazoles; Morphogenesis; Nervous System; Neurons; Nitric Oxide; Nitric Oxide Synthase; Oxadiazoles; Quinoxalines; Signal Transduction

In a hamster model (genetic symbol dt(sz)) of primary paroxysmal non-kinesiogenic dystonic choreoathetosis, recent studies have shown beneficial effects of glutamate and dopamine receptor antagonists. Nitric oxide (NO), synthesized from L-arginine by NO synthase in response to glutamate receptor activation, elicits cyclic GMP and modulates glutamate-mediated processes and striatal dopamine release. Therefore, the effects of NO synthase inhibitors and of L-arginine on severity of dystonia were investigated in dt(sz) hamsters in which dystonic attacks, characterized by twisting movements and postures, can be induced by stress. The NO synthase inhibitors N(G)-nitro-L-arginine (L-NNA), N(G)-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole significantly reduced the severity of dystonia. At antidystonic effective doses neither L-NNA nor L-NAME caused observable side effects, whereas 7-nitroindazole exerted moderate reduction of locomotor activity. The antidystonic effect of L-NAME was reversed by co-administration of the NO precursor L-arginine. However, L-arginine administered alone did not exert any effect on severity of dystonia. Cerebellar cyclic GMP levels in brains of mutant hamsters in comparison to non-dystonic control hamsters did not significantly differ, but the cerebellar cyclic GMP levels tended to be increased in dt(sz) hamsters during a dystonic attack. L-NAME significantly decreased the cerebellar cyclic GMP levels in both dt(sz) and control hamsters. Although an overproduction of NO is probably not critically involved in the pathogenesis of paroxysmal dystonia, it may contribute to the manifestation of dystonic attacks, as indicated by the antidystonic effects of NO synthase inhibitors. Peripheral side effects may limit the clinical use of NO synthase inhibitors, but more selective inhibitors of the neuronal NO synthase should be considered as interesting candidates for the treatment of paroxysmal dystonia.

Topics: Animals; Brain Chemistry; Cricetinae; Cyclic GMP; Dopamine; Dystonia; Enzyme Inhibitors; Indazoles; Motor Activity; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitroarginine; Receptors, N-Methyl-D-Aspartate

Cirrhosis is typically associated with a hyperdynamic circulation consisting of low blood pressure, low systemic vascular resistance (SVR), and high cardiac output. We have recently reported that nonspecific inhibition of nitric oxide synthase (NOS) with nitro-L-arginine methyl ester reverses the hyperdynamic circulation in rats with advanced liver cirrhosis induced by carbon tetrachloride (CCl(4)). Although an important role for endothelial NOS (eNOS) is documented in cirrhosis, the role of neuronal NOS (nNOS) has not been investigated. The present study was carried out to specifically investigate the role of nNOS during liver cirrhosis. Specifically, physiological, biochemical, and molecular approaches were employed to evaluate the contribution of nNOS to the cirrhosis-related hyperdynamic circulation in CCl(4)-induced cirrhotic rats with ascites. Cirrhotic animals had a significant increase in water and sodium retention. In the aorta from cirrhotic animals, both nNOS protein expression and cGMP concentration were significantly elevated compared with control. Treatment of cirrhotic rats for 7 days with the specific nNOS inhibitor 7-nitroindazole (7-NI) normalized the low SVR and mean arterial pressure, elevated cardiac index, and reversed the positive sodium balance. Increased plasma arginine vasopressin concentrations in the cirrhotic animals were also repressed with 7-NI in association with diminished water retention. The circulatory changes were associated with a reduction in aortic nNOS expression and cGMP. However, 7-NI treatment did not restore renal function in cirrhotic rats (creatinine clearance: 0.76 +/- 0.03 ml. min(-1). 100 g body wt(-1) in cirrhotic rats vs. 0.79 +/- 0.05 ml. min(-1). 100 g body wt(-1) in cirrhotic rats+7-NI; P NS. ). Taken together, these results indicate that nNOS-derived NO contributes to the development of the hyperdynamic circulation and fluid retention in cirrhosis.

Topics: Animals; Arginine Vasopressin; Ascites; Blotting, Western; Cyclic GMP; Enzyme Inhibitors; Hemodynamics; Indazoles; Kidney; Kidney Function Tests; Liver Cirrhosis, Experimental; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Osmolar Concentration; Rats; Rats, Sprague-Dawley; Sodium; Vasodilation

Topics: Anesthetics, Inhalation; Cerebellum; Cyclic GMP; Humans; Indazoles; Methyl Ethers; Pulmonary Alveoli; Sevoflurane

We investigated whether the parafascicular thalamic nucleus and the prefrontal cortex, the two major excitatory inputs to the striatum, modulate the nitric oxide/cyclic GMP pathway in rat striatum. Electrical stimulation (10 pulses of 0.5 ms, 10 V applied at 10 Hz, 140 microA) delivered bilaterally to the parafascicular thalamic nucleus for a total of 4, 10 and 20 min, time-dependently facilitated cyclic GMP output in the dorsal striatum of freely moving rats, assessed by trans-striatal microdialysis. Electrical stimulation to the prefrontal cortex for a total duration of 20 min did not affect striatal cyclic GMP levels. The facilitatory effect observed after electrical stimulation of the parafascicular thalamic nucleus was blocked by co-perfusion with tetrodotoxin, suggesting that the effect is mediated by neuronal process(es). The non-competitive N-methyl-D-aspartate receptor antagonist, dizocilpine maleate (30 microM infused into the dorsal striatum), and the competitive one, 3-[(R)-carboxypiperazin-4-yl]-propyl-phosphonic acid (50 microM infused), but not local perfusion of the alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid antagonist, 6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione (15 microM perfused locally), abolished the cyclic GMP response in the striatum. The nitric oxide synthase inhibitor, 7-nitroindazole, applied locally (1 mM), blocked the electrically evoked increase in striatal extracellular cyclic GMP. This increase was also prevented by local application (100 and 300 microM) of 1H-(1,2,4)-oxadiazolo-(4,3a)-quinoxalin-1-one, a selective inhibitor of soluble guanylyl cyclase. The results provide direct functional evidence of selective thalamic facilitation of the nitric oxide/cyclic GMP pathway in the dorsal striatum, through activation of N-methyl-D-aspartate receptors.

Topics: Animals; Cyclic GMP; Electric Stimulation; Electrodes, Implanted; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Guanylate Cyclase; Indazoles; Male; Microdialysis; Neostriatum; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Prefrontal Cortex; Rats; Rats, Inbred Strains; Receptors, AMPA; Receptors, N-Methyl-D-Aspartate; Tetrodotoxin; Thalamic Nuclei

Previous experimental findings have led to the suggestion that guanosine 3',5'-cyclic monophosphate (cGMP) plays a permissive role in hypercapnic cerebral vasodilation. However, we recently reported that the technique used to reveal a permissive role for cGMP [cGMP repletion in the presence of nitric oxide synthase (NOS) inhibition] created a situation where CO(2) reactivity was normalized but where different mechanisms (i.e., K(+) channels) participated in the response. In the present study, we examined whether that nascent K(+)-channel dependence is related in any way to an increase in the influence of the miconazole-inhibitable cytochrome P-450 epoxygenase pathway. Using intravital microscopy and a closed cranial window system in adult rats, we measured pial arteriolar diameters during normo- and hypercapnia, first in the absence and then in the presence of a neuronal NOS (nNOS) inhibitor [7-nitroindazole (7-NI)]. This was followed by suffusion of a cGMP analog and then cGMP plus miconazole. Separate groups of rats were used to evaluate whether miconazole either alone or in the presence of 8-bromoguanosine 3', 5'-cyclic monophosphate (8-BrcGMP) or its vehicle (0.1% ethanol) had any effect on CO(2) reactivity and whether miconazole affected K(+)-channel opener-induced dilations. Hypercapnic (arterial PCO(2), congruent with65 mmHg) pial arteriolar dilations, as expected, were reduced by 70-80% with 7-NI and restored with cGMP repletion. CO(2) reactivity was again attenuated after miconazole introduction. Miconazole, with and without 8-BrcGMP, and its vehicle had no influence on pial arteriolar CO(2) reactivity in the absence of nNOS inhibition combined with cGMP repletion. Miconazole alone also did not affect vasodilatory responses to K(+)-channel openers. Thus present results suggest that the nascent K(+)-channel dependence of the hypercapnic response found in our earlier study may be related to increased epoxygenase activity. The specific reasons why the pial arteriolar CO(2) reactivity gains a K(+)-channel and epoxygenase dependence only under conditions of nNOS inhibition and cGMP restoration remain to be identified. These findings again call into question the interpretations applied to data collected in studies evaluating potential permissive actions of cGMP or NO.

Topics: Animals; Arterioles; Carbon Dioxide; Cyclic GMP; Drug Combinations; Enzyme Inhibitors; Hypercapnia; Indazoles; Miconazole; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Pia Mater; Potassium Channels; Rats; Rats, Sprague-Dawley; Reference Values; Vasodilation

We evaluated the effects of superfusing 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), eNOS null (B) an inhibitor of soluble guanylyl cyclase, and 7-nitroindazole sodium (7-NI), a selective neuronal nitric oxide synthase (nNOS) inhibitor, on the acetylcholine (ACh) response in endothelial NOS (eNOS) null mice. Pial arteriolar diameter was measured by intravital microscopy through a closed cranial window under alpha-chloralose anesthesia. NOS activity was measured by [3H]arginine-to-[3H]citrulline conversion in subjacent cortex in vitro. The density and distribution of muscarinic receptors in the brain were determined by quantitative [3H]quinuclidinyl benzilate autoradiography and did not differ between the eNOS mutants and wild-type mice. ACh superfusion (1 and 10 microM) dose dependently dilated pial arterioles in eNOS null and wild-type mice. ODQ (10 microM) attenuated ACh-induced dilation in both eNOS mutants (41% decrease at 10 microM ACh, P < 0.01, n = 6) and wild-type strains (n = 5 per group). By contrast, topical superfusion of 7-NI (100 microM) attenuated the ACh response in eNOS mutants only (66%, P < 0.05, and 25% decrease, P < 0.05, at 1 and 10 microM ACh, respectively). Our findings suggest that nNOS-guanosine 3',5'-cyclic monophosphate (cGMP)-dependent pathways dilate pial arterioles by compensatory mechanisms after eNOS gene disruption.

Topics: Acetylcholine; Animals; Arginine; Arterioles; Autoradiography; Brain; Citrulline; Cyclic GMP; Endothelium, Vascular; Enzyme Inhibitors; Indazoles; Mice; Mice, Knockout; Neurons; Nitric Oxide Synthase; Pia Mater; Quinuclidinyl Benzilate; Receptors, Muscarinic; Vasodilation

1. Intraplantar injection of carrageenan (150 microl, 1-3% w/v) in the rat resulted in a dose-related increase in hindpaw weight (oedema) characterized by a rapid 'early' phase (up to 2.5 h) response followed by a more sustained 'late' phase (2-6 h) response. No change in weight of either the contralateral (i.e. noninjected) hindpaw or hindpaws injected with saline was observed. 2. Six hours after intraplantar injection of carrageenan (1-3% w/v) hindpaw constitutive (i.e. calcium-dependent) nitric oxide synthase (cNOS) activity (determined ex vivo as the conversion of radiolabelled L-arginine to radiolabelled citrulline) was increased (e.g. 2% w/v; 0.64+/-0.08 pmol citrulline mg(-1) protein 15 min(-1) c.f. 0.08+/-0.04 pmol citrulline mg(-1) protein 15 min(-1) in saline-injected, control animals, n=4, P<0.05). Carrageenan injection also resulted in the appearance in hindpaw homogenates of inducible (i.e. calcium-independent) nitric oxide synthase (iNOS, e.g. 2% w/v; 0.67+/-0.14 pmol citrulline mg(-1) protein 15 min(-1), n=4). Hindpaw cyclic GMP concentration was also significantly increased 6 h after intraplantar injection of carrageenan (e.g. 2% w/v; 379.6+/-26.8 fmol mg(-1) protein c.f. 261.8+/-42.2 fmol mg(-1) protein, in saline-injected, control animals, n=4, P<0.05). 3. Pretreatment (5-25 mg kg(-1), i.p., 30 min before carrageenan, 2% w/v) of animals with L-N(G) nitro arginine methyl ester (L-NAME; isoform nonselective inhibitor of NOS) or 7-nitro indazole (7-NI; inhibitor of neuronal NOS, nNOS) caused dose-related inhibition of both the early (2 h) and late (6 h) phase hindpaw oedema, associated with reduced hindpaw iNOS and cNOS activity and cyclic GMP concentration in animals killed at 6 h. Administration of 7-NI (5-25 mg kg(-1), i.p.) to animals 2.5 h after intraplantar carrageenan (2% w/v) injection (i.e. at the end of the early phase oedema response) produced dose-related inhibition of the late phase response. 4. Pretreatment (5-25 mg kg(-1), i.p., 30 min before carrageenan, 2% w/v) of animals with L-N6-iminoethyllysine (L-NIL, selective inhibitor of iNOS) (5-25 mg kg(-1)) failed to affect the early phase hindpaw oedema response but did produce a dose-related inhibition of the late phase oedema. L-NIL pretreatment also inhibited the carrageenan-induced increase in both hindpaw iNOS and cNOS activity as well as the rise in hindpaw cyclic GMP concentration. 5. The present experiments demonstrate an anti-inflammatory effect of 7-NI as evidenced by

Topics: Animals; Carrageenan; Cyclic GMP; Edema; Enzyme Inhibitors; Hindlimb; Indazoles; Lysine; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Rats; Rats, Wistar

The conclusion that cyclic 3'-5 guanosine monophosphate (cGMP) functions in a 'permissive' manner in promoting cerebrovasodilation during hypercapnia was based on findings showing that the nitric oxide synthase (NOS) inhibitor-induced repression of the CO2 response could be reversed upon addition of exogenous cGMP. We hypothesized that the action of cGMP revealed in those studies does not define its normal role in hypercapnic cerebral vasodilation, but rather is a unique function of the artificial situation of NOS inhibition coupled with cGMP repletion. Thus, although CO2 reactivity may be the same in normal versus cGMP-repleted animals, the factors contributing to that response may differ. To test that possibility, the effects of calcium-dependent (KCa) or ATP-sensitive (KATP) potassium channel blockers on pial arteriolar CO2 reactivity, in vivo, were evaluated in the presence and absence of NOS inhibition plus administration of a cGMP analogue. Pial arteriolar diameter changes in hypercapnia were measured in three principal groups of anesthetized rats: (I) KCa channel-inhibited (via iberiotoxin); (II) KATP channel-inhibited (via glibenclamide); and (III) controls. Group I and II rats were further divided into: (a) those treated with the neuronal NOS (nNOS) inhibitor, 7-nitroindazole (7-NI), followed by successive suffusions of the cGMP analogue, 8-bromo-cGMP (8Br-cGMP) and 8Br-cGMP+K-channel blocker; and (b) rats where 7-NI and 8Br-cGMP applications were omitted. Group III rats were divided into time and 8Br-cGMP controls. Hypercapnia (PCO2 congruent with60 mmHg, 3 min)-induced dilations were reduced by 70-80% following 7-NI and restored by 8Br-cGMP. That restoration was reversed by both K-channel blockers. In the absence of 7-NI and exogenous cGMP, CO2 reactivity was unaffected by K-channel inhibition. These findings confirmed that nNOS-derived NO is critically important to the hypercapnic reactivity of cerebral arterioles, and that cGMP repletion, following NOS inhibition, could restore CO2 reactivity. The observation that KCa and KATP channel blockade did not alter CO2 reactivity under baseline conditions, but attenuated CO2 reactivity only in the presence nNOS inhibition (and cGMP repletion), suggests that multiple, redundant, and interactive mechanisms participate in CO2-induced vasodilation. These results also imply that current strategies for revealing permissive actions of cGMP (or NO) may need to be re-evaluated.

Topics: Adenosine Triphosphate; Animals; Benzimidazoles; Blood Pressure; Calcium; Carbon Dioxide; Cerebral Arteries; Cromakalim; Cyclic GMP; Glyburide; Hydrogen-Ion Concentration; Hypercapnia; Indazoles; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Penicillamine; Peptides; Pia Mater; Potassium Channel Blockers; Potassium Channels; Rats; Rats, Sprague-Dawley; Substrate Specificity; Vasodilation

Although inhibition of nitric oxide synthase (NOS) has been reported to be antinociceptive and to reduce the threshold of general anesthesia, the mechanism of action is largely unknown. Specifically, the relation between the minimum alveolar concentration (MAC)-reducing effects of NOS inhibition and cyclic guanosine monophosphate (cGMP) concentrations in the brain has not been defined. To further characterize the effects of NOS inhibition, the authors studied the relation between the MAC of sevoflurane and the cGMP concentration of the brain after acute and chronic treatment with a neuronally selective NOS inhibitor, 7-nitroindazole (7-NI).. Sevoflurane MAC and cerebellar cGMP concentrations were determined in mice after acute intraperitoneal administration or after 1, 2, 3, and 4 days of gavage feeding of 7-NI. After acute or chronic treatment with 7-NI, the mice were separated into two groups. Sevoflurane MAC was measured by a tail-clamp method in the first group, and cerebellar cGMP concentrations were measured by enzyme-linked immunosorbent assay in the second group of the mice.. In mice, acute intraperitoneal administration of 7-NI dose dependently decreased sevoflurane MAC and cerebellar cGMP; and 4-day-long gavage feeding with 7-NI (500 mg/ kg, every 8 h) time dependently decreased cerebellar cGMP, but sevoflurane MAC was reduced only for the first 2 days and returned to its baseline after 3 days of 7-NI feeding.. Although an acute selective inhibition of neuronal NOS decreases sevoflurane MAC and cerebellar cGMP concentrations in mice, there was a dissociation between the two parameters during long-term neuronal NOS inhibition. There may be cGMP-independent compensatory mechanisms that mediate nociception when NOS is chronically inhibited.

Topics: Anesthetics, Inhalation; Animals; Cerebellum; Cyclic GMP; Enzyme Inhibitors; Indazoles; Lung; Methyl Ethers; Mice; Nitric Oxide Synthase; Sevoflurane

Nitric oxide (NO) acts via soluble guanylyl cyclase to increase cyclic GMP (cGMP), which can regulate various targets including protein kinases. Western blotting showed that type II cGMP-dependent protein kinase (cGK II) is widely expressed in various brain regions, especially in the thalamus. In thalamic extracts, the phosphorylation of several proteins, including cGK II, was increased by exogenous NO or cGMP. In vivo pretreatment with a NO synthase inhibitor reduced the phosphorylation of cGK II, and this could be reversed by exogenous NO or cGMP. Conversely, brainstem electrical stimulation, which enhances thalamic NO release, caused a NO synthase-dependent increase in the phosphorylation of thalamic cGK II. These results indicate that endogenous NO regulates cGMP-dependent protein phosphorylation in the thalamus. The activation of cGKII by NO may play a role in thalamic mechanisms underlying arousal.

Topics: Animals; Arousal; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Enzyme Inhibitors; GABA Modulators; Indazoles; Male; Nitric Oxide; Nitric Oxide Synthase; Pentobarbital; Phosphorylation; Rats; Rats, Wistar; Thalamus

In this study, the N-Methyl-D-Aspartate (NMDA) receptor-dependent nitric oxide and cyclic GMP (cGMP) synthesis in the course of reperfusion after 5 min of ischemia in gerbil brain hemispheres and cerebellum were investigated. Moreover, the role of the neuronal isoform of nitric oxide (NO) synthase (nNOS) in liberation of NO in postischemic brain and the involvement of NO in membrane lipoperoxidations activated during reperfusion were evaluated. Enhancement of Ca2+/calmodulin-regulated NOS activity and cGMP level in brain hemispheres and in cerebellum during reperfusion was found to be coupled to the activation of the NMDA receptor. cGMP concentration 40% above the control level was observed to persist up to 7 days after ischemia. The amount of conjugated double bounds in membrane lipids and the level of thiobarbituric acid reactive substances were increased exclusively in brain hemispheres, indicating activation of lipid peroxidation. The NMDA receptor antagonist, MK-801, eliminated, and a rather selective nNOS inhibitor, 7-Nitroindazole (7-NI) attenuated, NMDA receptor-evoked enhancement of NOS activity and cGMP level in brain hemispheres and in cerebellum during reperfusion. Moreover, 7-NI decreased significantly membrane lipid peroxidation during the early time of reperfusion. Histological examination demonstrated that 7-NI protects against death a selected population of neuronal cells in CA1 layer of hippocampus. It is suggested that NMDA receptor dependence of NO release during reperfusion is responsible for the degeneration of some populations of neurons and that the effect is mediated by activation of free radical formation and lipid peroxidation. Moreover, in cerebellum, ischemia-evoked activation of glutamatergic system stimulates NO-dependent signal transmission. Our results indicated that 7-NI has a significant ameliorating effect on biochemical alterations evoked by ischemia, suggesting nNOS inhibitors as a potential therapeutic agents in reperfusion injury.

Topics: Animals; Brain Ischemia; Cerebellum; Cerebral Cortex; Cyclic GMP; Dizocilpine Maleate; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Gerbillinae; Indazoles; Lipid Peroxidation; Male; Membrane Lipids; Neuroprotective Agents; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Prosencephalon; Receptors, N-Methyl-D-Aspartate; Reperfusion Injury; Signal Transduction; Thiobarbituric Acid Reactive Substances

Electrical stimulation of cerebellar parallel fibers (PF) increases cerebellar blood flow (BFcrb), a response that is attenuated by glutamate receptor antagonists and NO synthase (NOS) inhibitors. We investigated whether administration of NO donors could counteract attenuation by NOS inhibitors of vasodilation produced by PF stimulation. In halothane-anesthetized rats the cerebellar cortex was exposed and superfused with Ringer solution. PF were stimulated with microelectrodes (100 microA, 30 Hz), and BFcrb was recorded by a laser-Doppler probe. During Ringer superfusion, PF stimulation increased BFcrb by 56 +/- 7% and hypercapnia by 72 +/- 5% (n = 5). Superfusion with the nonselective NOS inhibitor N-nitro-L-arginine (L-NNA, 1 mM) reduced resting BFcrb and attenuated the response to PF stimulation (-47 +/- 5%) and hypercapnia (-46 +/- 7%; PCO2 = 50-60 mmHg). After L-NNA, superfusion with the NO donors 3-morpholinosydnonimine (100 microM, n = 5) or S-nitroso-N-acetyl-penicillamine (5 microM, n = 5) reestablished resting BFcrb (P > 0.05 vs. before L-NNA) and reversed L-NNA-induced attenuation of the response to hypercapnia (P > 0.05 vs. before L-NNA) but not PF stimulation (P > 0.05 vs. after L-NNA). Similar results were obtained when NOS activity was inhibited with the inhibitor of neuronal NOS 7-nitroindazole (50 mg/kg i.p.). Like NO donors, the guanosine 3',5'-cyclic monophosphate analog 8-bromoguanosine 3',5'-cyclic monophosphate (n = 5), administered after L-NNA, restored resting BFcrb and counteracted inhibition of the response to hypercapnia but not PF stimulation. In contrast to NO donors and 8-bromoguanosine 3',5'-cyclic monophosphate, the NO-independent vasodilator papaverine (100 microM, n = 5) had no effect on attenuation of responses to PF stimulation or hypercapnia. Thus NO donors are unable to reverse the effect of NOS inhibition on vasodilation produced by PF stimulation. The data support the hypothesis that the vascular response to PF stimulation, at variance with hypercapnia, requires NOS activation and NO production. Thus NO plays an obligatory role in vasodilation produced by increased functional activity in cerebellar cortex.

Topics: Animals; Blood Pressure; Carbon Dioxide; Cerebellum; Cyclic GMP; Electric Stimulation; Enzyme Inhibitors; Glutamic Acid; Hyperemia; Indazoles; Male; Molsidomine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxygen; Papaverine; Partial Pressure; Penicillamine; Rats; Rats, Sprague-Dawley; Regional Blood Flow; S-Nitroso-N-Acetylpenicillamine; Vasodilation

The angiotensin AT2 receptor modulates renal production of cyclic guanosine 3',5'-monophosphate (cGMP; J. Clin. Invest. 1996. 97:1978-1982). In the present study, we hypothesized that angiotensin II (Ang II) acts at the AT2 receptor to stimulate renal production of nitric oxide leading to the previously observed increase in cGMP. Using a microdialysis technique, we monitored changes in renal interstitial fluid (RIF) cGMP in response to intravenous infusion of the AT2 receptor antagonist PD 123319 (PD), the AT1 receptor antagonist Losartan, the nitric oxide synthase (NOS) inhibitor nitro--arginine-methyl-ester (-NAME), the specific neural NOS inhibitor 7-nitroindazole (7-NI), or Ang II individually or combined in conscious rats during low or normal sodium balance. Sodium depletion significantly increased RIF cGMP. During sodium depletion, both PD and -NAME caused a similar decrease in RIF cGMP. Combined administration of PD and -NAME decreased RIF cGMP to levels observed with PD or -NAME alone or during normal sodium intake. During normal sodium intake, Ang II caused a twofold increase in RIF cGMP. Neither PD nor -NAME, individually or combined, changed RIF cGMP. Combined administration of Ang II and either PD or -NAME produced a significant decrease in RIF cGMP compared with that induced by Ang II alone. Combined administration of Ang II, PD, and -NAME blocked the increase in RIF cGMP produced by Ang II alone. During sodium depletion, 7-NI decreased RIF cGMP, but the reduction of cGMP in response to PD alone or PD combined with 7-NI was greater than with 7-NI alone. During normal sodium intake, 7-NI blocked the Ang II-induced increase in RIF cGMP. PD alone or combined with 7-NI produced a greater inhibition of cGMP than did 7-NI alone. During sodium depletion, 7-NI (partially) and -NAME (completely) inhibited RIF cGMP responses to -arginine. These data demonstrate that activation of the renin- angiotensin system during sodium depletion increases renal nitric oxide production through stimulation by Ang II at the angiotensin AT2 receptor. This response is partially mediated by neural NOS, but other NOS isoforms also contribute to nitric oxide production by this pathway.

Topics: Angiotensin II; Angiotensin Receptor Antagonists; Animals; Biphenyl Compounds; Blood Pressure; Cyclic GMP; Enzyme Inhibitors; Extracellular Space; Female; Imidazoles; Indazoles; Kidney; Losartan; Microdialysis; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Pyridines; Rats; Rats, Sprague-Dawley; Receptors, Angiotensin; Renin-Angiotensin System; Sodium; Tetrazoles

Regulation of agonist-activated Ca2+ influx by the NOS pathway through generation of cGMP is being found in an increasing number of cell types. In the present work, we examined the role of the NOS pathway in agonist-evoked [Ca2+]i oscillations and attempted to identify the NOS isoform most likely to regulate Ca2+ influx. For this, we first show that two Ca(2+)-mobilizing agonists acting on pancreatic acinar cells, bombesin (BS) and the cholecystokinin analog CCK-JMV-180 (CCKJ), evokes different type of [Ca2+]i oscillations. The BS-evoked [Ca2+]i oscillations rapidly became acutely dependent on the presence of extracellular Ca2+, whereas the CCKJ-evoked oscillations continue for long periods of time in the absence of Ca2+ influx. This differential behavior allowed us to isolate Ca2+ influx and study its regulation while controlling for non specific effects on all other Ca2+ transporting events involved in generating [Ca2+]i oscillations. Inhibitors of selective steps in the NOS pathway inhibited agonist-induced cGMP production. The inhibitors were then used to show that scavenging NO with reduced hemoglobin, inhibition of guanylyl cyclase with 1H-[1,2,4] oxadiazolo[4,3-a] quinoxaline-1-one (ODQ) and inhibition of protein kinase G with Rp-8-pCPT-cGMPS inhibited [Ca2+]i oscillations evoked by BS but not those evoked by CCKJ. These findings were extended to duct and acinar cells of the SMG. In these cells, Ca(2+)-mobilizing agonists stimulate large Ca2+ influx, which was inhibited by all inhibitors of the NOS pathway. Western blot analysis and immunolocalization revealed that the cells did not express iNOS, eNOS was expressed only in blood vessels and capillaries whereas nNOS was expressed at high levels next to the plasma membrane of all cells. Accordingly, the nNOS inhibitor 7-nitroindazole (7-NI) inhibited BS- but not CCKJ-evoked [Ca2+]i oscillations and Ca2+ influx into SMG acinar and duct cells. Thus, together, our findings favor nNOS as the isoform activated by the Ca2+ released from internal stores to generate cGMP and regulate Ca2+ influx.

Topics: Animals; Blotting, Western; Bombesin; Calcium; Cells, Cultured; Cholecystokinin; Cyclic GMP; Immunohistochemistry; Indazoles; Nitric Oxide Synthase; Pancreatic Ducts; Rats; Signal Transduction; Submandibular Gland

Nitric oxide (NO) contributes to hypoxia-induced pial artery dilation, at least in part, via the formation of guanosine 3',5'-cyclic monophosphate (cGMP) and subsequent release of Met-enkephalin and Leu-enkephalin in the newborn pig. In separate studies, these opioids were also observed to elicit NO-dependent pial dilation. The present study was designed to investigate the role of the neuronal isoform of NO synthase (NOS) in hypoxic pial dilation, associated opioid release, and opioid dilation in piglets equipped with a closed cranial window. Tetrodotoxin (10(-6) M) attenuated the dilation resulting from hypoxia (PO2 approximately 35 mmHg; 25 +/- 1 vs. 14 +/- 1%). Similarly, 7-nitroindazole, sodium salt (7-NINA, 10(-6) M), a purported neuronal NOS inhibitor, attenuated hypoxic pial dilation (26 +/- 1 vs. 14 +/- 2%). Hypoxic dilation was accompanied by elevated cerebrospinal (CSF) cGMP, which was blocked by 7-NINA (433 +/- 19 and 983 +/- 36 vs. 432 +/- 19 and 441 +/- 19 fmol/ml for control and hypoxia in absence and presence of 7-NINA, respectively). Additionally, hypoxic dilation was also accompanied by elevated CSF Met-enkephalin, which was attenuated by 7-NINA (1,027 +/- 47 and 2,871 +/- 134 vs. 779 +/- 78 and 1,551 +/- 42 pg/ml for control and hypoxia in absence and presence of 7-NINA, respectively). In contrast, Met-enkephalin (10(-10), 10(-8), and 10(-6) M) induced dilation that was unchanged by 7-NINA (7 +/- 1, 12 +/- 1, and 18 +/- 1 vs. 6 +/- 1, 10 +/- 1, and 17 +/- 1%, respectively). N-methyl-D-aspartate (NMDA, 10(-8) and 10(-6) M), an activator of neuronal NOS, induced pial dilation that was blocked by 7-NINA (10 +/- 1 and 20 +/- 2 vs. 1 +/- 1 and 2 +/- 1%, respectively). However, sodium nitroprusside-induced dilation was unchanged by 7-NINA. These data indicate that neuronal NOS contributes to hypoxic pial artery dilation but not to opioid-induced dilation. Furthermore, these data suggest that neuronally derived NO contributes to hypoxic dilation, at least in part, via formation of cGMP and the subsequent release of opioids.

Topics: Animals; Cerebral Arteries; Cyclic GMP; Endorphins; Enkephalins; Enzyme Inhibitors; Female; Hypoxia; Indazoles; Male; Neurons; Nitric Oxide; Nitric Oxide Synthase; Pia Mater; Swine; Tetrodotoxin; Vasodilation

The effects of 7-nitroindazole, a putative selective inhibitor of neuronal nitric oxide (NO) synthase and zaprinast, a cGMP-selective phosphodiesterase inhibitor, were evaluated on recognition memory of rats in the object recognition test. This test is based on the differential exploration of a new and a familiar object. Two doses of 7-nitroindazole (10 and 30 mg/kg) and zaprinast (3 and 10 mg/kg) were used. The substances were administered i.p. immediately after the exposure to two identical objects, i.e., at the start of the delay interval. After a delay interval of 1 h, control rats spent more time exploring the new object which demonstrates that they recognized the familiar one. Both doses of 7-nitroindazole impaired the discrimination between the two objects after the 1 h interval. After a 4 h interval, control rats did not discriminate between the objects. The highest dose of zaprinast facilitated object recognition after the 4 h interval. In addition, this dose of zaprinast (10 mg/kg) reversed the recognition memory deficit induced by 7-nitroindazole (10 mg/kg) at the 1 h interval. The highest dose of 7-nitroindazole slightly increased mean arterial blood pressure 1 h after its administration. 4 h after administration of zaprinast (10 mg/kg), mean arterial blood pressure was also slightly increased, but not after 1 h after zaprinast administration. However, these effects on blood pressure do not explain the differential effects on object recognition memory. These results therefore suggest that NO-cGMP signal transduction is involved in object recognition memory independently of its cardiovascular role. Finally, since 7-nitroindazole affected mean arterial blood pressure it can not be regarded as a selective inhibitor of neuronal NO synthase.

Topics: Animals; Blood Pressure; Cyclic GMP; Drug Interactions; Exploratory Behavior; Indazoles; Male; Memory; Nitric Oxide; Nitric Oxide Synthase; Phosphodiesterase Inhibitors; Purinones; Rats; Signal Transduction; Visual Perception

The present behavioral study was undertaken to investigate whether neuronal nitric oxide (NO) synthase mediates the abnormal consequences of increased NMDA receptor-mediated synaptic transmission in models of postural tremor, Parkinson's disease and epilepsy. We used 7-nitroindazole, a selective inhibitor of neuronal NO synthase, and NG-nitro-L-arginine (L-NAME), an unspecific NO synthase inhibitor, and compared their action with that of the competitive NMDA receptor antagonist 3-[(R)-2-carboxypiperazin-4-yl]-prop-2-enyl-1-phosphonic acid (D-CPPene). In both mice and rats, 7-nitroindazole, L-NAME and D-CPPene dose dependently reversed the harmaline-induced increase of cerebellar cyclic guanosine-5'-monophosphate (cGMP) levels. For subsequent behavioral experiments we used doses of 7-nitroindazole, L-NAME and D-CPPene which were equipotent in preventing harmaline-induced cGMP increase. Harmaline-induced tremor in mice and rats was suppressed by D-CPPene, but not by 7-nitroindazole or by L-NAME. This effect of D-CPPene was not due to unspecific suppression of motor activity, since D-CPPene did not affect locomotor activity at doses which reduced tremor. D-CPPene, but not 7-nitroindazole and L-NAME potentiated the antiparkinsonian action of the dopamine agonist lisuride in rats with unilateral 6-hydroxydopamine lesions of the substantia nigra. D-CPPene antagonized seizures induced by intracerebroventricular injection of NMDA in mice. In contrast, 7-nitroindazole and L-NAME had only a tendency to prevent seizures and to delay the latency to onset of seizures. We conclude from these results that neuronal NO synthase does not serve as a major mediator of increased NMDA receptor-mediated synaptic transmission in animal models of Parkinson's disease, postural tremor and epilepsy. The novel observation that D-CPPene suppresses harmaline-induced tremor leads us to suggest that NMDA receptor antagonists should be considered as novel therapeutics for postural tremor.

Topics: Animals; Anticonvulsants; Behavior, Animal; Brain; Cyclic GMP; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Harmaline; Hydroxydopamines; Indazoles; Lisuride; Locomotion; Male; N-Methylaspartate; Nitric Oxide Synthase; Nitroarginine; Piperazines; Rats; Receptors, N-Methyl-D-Aspartate; Seizures

The possible modulatory role of nitric oxide (NO) in neurogenic edema formation in rat paw skin, induced by electrical stimulation of the saphenous nerve, was investigated by using two NO synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI). Both L-NAME (100 mg/kg IV, P < .05) and 7-NI (10 mg/kg IV, P < .05) caused an L-arginine (100 mg/kg IV, P < .01)-reversible inhibition of neurogenic edema as measured by 125I-albumin accumulation, whereas D-NAME (inactive enantiomer of L-NAME) and 6-aminoindazole (structurally similar to 7-NI) were without inhibitory effect. L-NAME produced the predicted vasopressor effect (before, 115 +/- 18 mm Hg; 5 minutes after, 174 +/- 18 mm Hg; n = 6; P < .05), whereas 7-NI showed no significant increase in blood pressure (before, 96 +/- 9 mm Hg; 5 minutes after, 102 +/- 10 mm Hg; n = 6), and neither L-NAME nor 7-NI had any effect on basal or vasodilator calcitonin gene-related peptide (CGRP, 10 pmol per site)-stimulated local blood flow in rat skin, as measured by laser Doppler flowmetry. Furthermore, systemic and local 7-NI had no effect on edema formation induced by local administration of substance P (with or without CGRP) and histamine (with or without CGRP) in rat skin. Since 7-NI blocks edema produced by stimulation of the saphenous nerve, it is suggested that release of NO is involved in neurogenic edema formation, but the vasodilator action of NO is unimportant in this context.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Blood Pressure; Cyclic GMP; Endothelium, Vascular; Indazoles; Inflammation; Male; Microcirculation; NG-Nitroarginine Methyl Ester; Nitric Oxide; Rats; Rats, Wistar; Regional Blood Flow; Skin; Substance P

Bradykinin-induced activation of peripheral sensory fibres was studied using an in vitro preparation of the neonatal rat spinal cord with attached tail. Noxious heat stimulation, as well as the applications of bradykinin and capsaicin, to the tail evoked reproducible responses recorded as a depolarization of a lumbar ventral root. Prolonged administration of a supramaximal concentration of bradykinin invariably induced a complete but selective desensitization to a subsequent bradykinin challenge. Bradykinin-induced desensitization was significantly attenuated by concanavalin-A and the effect of concanavalin-A was prevented by alpha-methyl mannoside. Both cyclic GMP and sodium nitroprusside induced a long lasting reduction of bradykinin responsiveness in peripheral fibres. The effect of nitroprusside was prevented by concanavalin-A, and by methylene blue, an inhibitor of guanylyl cyclase. Methylene blue also reduced bradykinin-induced desensitization. L-arginine, but not D-arginine, induced a desensitization to bradykinin. On the other hand, 7-nitroindazole (7-NI, 200-500 nM), an inhibitor of NOS, reduced the desensitization of bradykinin responses but higher concentrations of 7-NI (IC50 = 6.7 +/- 0.9 microM) selectively attenuated responses to bradykinin. The effects of 7-NI were attenuated by L-arginine pretreatment. These data suggest that bradykinin-induced desensitization of peripheral sensory fibres is mediated in part via NO and cyclic GMP dependent mechanisms: possibly NO production is required for guanylate cyclase activation.

Topics: Animals; Animals, Newborn; Arginine; Bradykinin; Concanavalin A; Cyclic GMP; Indazoles; Methylene Blue; Nitric Oxide; Nitroprusside; Nociceptors; Rats; Receptors, Bradykinin; Spinal Cord