PubMed Health⌕ Search

Biomedical subjects

P K Moore

Publications and source records attributed to P K Moore.

At least 37 records · Page 2Linked to original sources
PubMed1996

Inhibition of nitric oxide synthase by isothioureas: cardiovascular and antinociceptive effects.

A range of substituted isothiourea compounds including S-isopropylisothiourea (IPTU), S-methylisothiourea (SMT), S-ethylisothiourea (ETU), N-pentylisothiourea (PTU), S-(2 aminoethyl)isothiourea (AETU), and S-acetamidoisothiourea (AATU) inhibit mouse spinal cord/cerebellar neuronal nitric oxide synthase (nNOS) and bovine aortic endothelial cell eNOS in vitro. IP administration of isothioureas increased mean arterial blood pressure of the urethane-anaesthetised mouse (rank order of effect: IPTU > ETU > SMT > AETU). PTU and AATU were without vasopressor activity. IPTU (50 mg/kg, IP) inhibited late phase formalin-induced hindpaw licking behaviour in the mouse while SMT (50 mg/kg, IP) was without effect. Neither compound influenced the formalin-induced increase in hindpaw weight reflecting a lack of significant peripheral antioedema effect in this model. IPTU (50 mg/kg, IP) but not SMT (50 mg/kg, IP) inhibited mouse spinal cord and cerebellar NOS activity measured ex vivo in animals killed 45 min after injection. The present study confirms the potent NOS inhibitory effect of selected substituted isothioureas in vitro. Little or no isoform selectivity (i.e., nNOS vs. eNOS) was apparent. The potent vasopressor effect of isothioureas indicates that these compounds may be of limited use as tools to study the role of nitric oxide in pain perception.

Analgesics↗
PubMed1996

Inhibition of nitric oxide synthase by 1-(2-trifluoromethylphenyl) imidazole (TRIM) in vitro: antinociceptive and cardiovascular effects.

1. The ability of a range of substituted imidazole compounds to inhibit mouse cerebellar neuronal nitric oxide synthase (nNOS), bovine aortic endothelial NOS (eNOS) and inducible NOS (iNOS) from lungs of endotoxin-pretreated rats was investigated. In each case the substrate (L-arginine) concentration employed was 120 nM. 2. 1-(2-Trifluoromethylphenyl) imidazole (TRIM) was a relatively potent inhibitor of nNOS and iNOS (IC50S of 28.2 microM and 27.0 microM respectively) but was a relatively weak inhibitor of eNOS (IC50, 1057.5 microM). The parent compound, imidazole, was a weak inhibitor of all three NOS isoforms (IC50S: nNOS, 290.6 microM; eNOS, 101.3 microM; iNOS, 616.0 microM). Substitution of imidazole with a phenyl group to yield I-phenylimidazole (PI) resulted in an isoform non-selective increase in inhibitory potency (IC50S: nNOS, 72.1 microM; eNOS, 86.9 microM; iNOS, 53.9 microM). Further substitution of the attached phenyl group resulted in an increase in nNOS and a decrease in eNOS inhibitory potency as in TRIM, 1-chlorophenylimidazole (CPI; IC50S: nNOS, 43.4 microM; eNOS, 392.3 microM; iNOS, 786.5 microM) and 1-(2,3,5,6-tetrafluorophenyl) imidazole (TETRA-FPI; IC50S; nNOS, 56.3 microM; eNOS, 559.6 microM; iNOS, 202.4 microM). 3. The ability of TRIM to inhibit mouse cerebellar nNOS activity in vitro was influenced by the concentration of L-arginine (0.12-10.0 microM) in the incubation medium. When mouse cerebellar nNOS was used as enzyme source a double reciprocal (Lineweaver-Burk) plot in the presence/absence of TRIM (50 microM) revealed a competitive inhibitory profile. The K(m) for L-arginine and the Ki for TRIM calculated from these data were 2.4 microM and 21.7 microM, respectively. The ability of TRIM to inhibit mouse cerebellar nNOS activity in vitro was unaffected by varying the time of exposure of the enzyme to TRIM from 0-60 min at 0 degree C. 4. TRIM exhibits potent antinociceptive activity in the mouse as evidenced by inhibition of acetic acid induced abdominal constrictions. The ED50 for TRIM following i.p. administration was 20 mg kg-1 (94.5 mumol kg-1). The antinociceptive effect of TRIM was reversed by pretreatment of animals with L-arginine (50 mg kg-1, i.p.) and was not accompanied by sedation, motor ataxia or behavioural changes (rearing, crossing, circling, dipping) as assessed by use of a box maze procedure. 5. L-NG nitro arginine methyl ester (L-NAME, 20 mg kg-1, i.v.) but not TRIM (0.5-20 mg kg-1, i.v.) increased mean arterial blood pressure (MAP) in the urethane-anaesthetized rat. 6. L-NAME (100 microM) potentiated the contractile response of the rabbit isolated aorta to phenylephrine (ED50; 0.084 +/- 0.01 microM in the presence and 0.25 +/- 0.05 microM in the absence of L-NAME; maximum response, 7.7 +/- 0.4 g in the presence and 5.6 +/- 0.5 g in the absence of L-NAME, n = 6, (P < 0.05) whilst TRIM (1-100 microM) was without effect. L-NAME (100 microM) but not TRIM (1-100 microM) also reduced carbachol-induced relaxation of the phenylephrine-precontracted rabbit aorta preparation. 7. L-NAME (50 microM) potentiated the vasoconstrictor effect of bolus-injected noradrenaline (10-1000 nmol) and reduced the vasodilator effect of carbachol (10 microM) added to the Krebs reservoir in the rat perfused mesentery preparation. L-NAME (50 microM) also reduced nitric oxide (NO) release (measured by chemiluminescence of nitrite in the Krebs perfusate) in response to noradrenaline (100 nmol; 53.8 +/- 4.0 pmol ml-1 in the presence and 84.8 +/- 8.0 pmol ml-1 in the absence of L-NAME, n = 15, P < 0.05) and carbachol (10 microM; 63.9 +/- 5.0 pmol ml-1 in the presence and 154.0 +/- 9.0 pmol ml-1 in the absence of L-NAME, n = 15, P < 0.05). TRIM (50 microM) did not affect either the vasoconstrictor response to noradrenaline or the vasodilator response to carbachol or the accompanying release of NO from the perfused rat mesentery.

Analgesics↗
PubMed1995

7-Nitro indazole derivatives are potent inhibitors of brain, endothelium and inducible isoforms of nitric oxide synthase.

The effect of 7-nitro indazole (7-NI) and a range of substituted indazole derivatives on nitric oxide synthase (NOS) enzyme activity in homogenates of rat cerebellum, bovine endothelial cells and lung from endotoxin-pretreated rats was investigated. 3-bromo 7-nitro indazole was either equipotent (IC50, 0.86 +/- 0.05 microM c.f. 0.78 +/- 0.2 microM, n = 6, P > 0.05) or approximately 4x (IC50, 0.17 +/- 0.01 microM c.f. 0.71 +/- 0.01 microM, n = 6, P < 0.05) or 20x (IC50, 0.29 +/- 0.01 microM c.f. 5.8 +/- 0.4 microM, n = 6, P < 0.05) more potent than 7-NI as an inhibitor of bovine endothelial, rat cerebellar and rat lung NOS enzyme activity respectively. 2,7-dinitro indazole also inhibited NOS in all three tissue sources with a potency similar to that of 7-NI. These results suggest that 3-bromo 7-NI and 2,7-dinitro indazole may prove to be useful additional tools with which to examine the biological properties of nitric oxide (NO).

Amino Acid Oxidoreductases↗
PubMed1995

Inhibition of nitric oxide synthase--potential for a novel class of therapeutic agent?

The free-radical gas nitric oxide (NO) plays an important role in a wide and diverse range of physiological processes. As progress is made in understanding the biological function of NO, there is growing interest in the possibility that inhibitors of NO synthase (NOS) may be of clinical use in the therapy of certain disease states. The search for novel and clinically relevant inhibitors of this enzyme represents a truly multidisciplinary approach to drug screening and will no doubt benefit from the application of recombinant DNA (rDNA) technology.

Amino Acid Oxidoreductases↗
PubMed1995

Increased striatal dopamine efflux in vivo following inhibition of cerebral nitric oxide synthase by the novel monosodium salt of 7-nitro indazole.

The role of nitric oxide (NO) in striatal dopamine release has been controversial. Most NO synthase inhibitors affect more than one isoform of the enzyme and exert vasoconstrictor effects which may also affect striatal dopamine function. We now report on the effect of a soluble monosodium salt of the selective brain NO synthase inhibitor 7-nitro indazole (7-NINA). Using 7-NINA the first study of selective inhibition of the brain isoform of NO synthase on dopamine efflux in rat striatum was undertaken by use of in vivo microdialysis. Perfusion with 7-NINA (1 mM) increased striatal dopamine efflux. The effect of 7-NINA was partially antagonized (67%) by co-perfusion with L-arginine (1 mM), the precursor of NO formation in vivo. This suggests that 7-NINA induces a competitive inhibition of NO synthase activity. These data show that endogenous NO has an inhibitory effect on striatal dopamine efflux in vivo.

Amino Acid Oxidoreductases↗
PubMed1995

The antinociceptive effect of 1-(2-trifluoromethylphenyl) imidazole (TRIM), a potent inhibitor of neuronal nitric oxide synthase in vitro, in the mouse.

1-(2-trifluoromethylphenyl)imidazole (TRIM) is a potent inhibitor of neuronal (mouse cerebellar) and inducible (lung from endotoxin-pretreated rats) isoforms of nitric oxide synthase (NOS) with IC50 values of 28.2 microM and 27.0 microM, respectively. In contrast, TRIM is a poor inhibitor of bovine aortic endothelial NOS with an IC50 of 1057.5 microM. TRIM (10-50 mg kg-1) administered i.p. exhibits dose-related antinociceptive activity in the mouse (assessed as inhibition of late phase formalin-induced hindpaw licking behaviour) with an ED50 of 85.8 mumol kg-1. In contrast, TRIM (50 mg kg-1, i.p.) failed to influence mean arterial blood pressure in the urethane-anaesthetized mouse. Thus, TRIM may be of use as an experimental tool with which to investigate the biological roles of nitric oxide (NO) within the central nervous system.

Analgesics↗
PubMed1995

An endogenous protectant effect of cardiac cyclic GMP against reperfusion-induced ventricular fibrillation in the rat heart.

1. After a period of myocardial ischaemia, reperfusion of the myocardium can elicit cardiac arrhythmias. Susceptibility to these arrhythmias declines with time, such that a preceding period of more than approximately 40 min ischaemia is associated with few reperfusion-induced arrhythmias. We have tested the hypothesis that this decline in susceptibility occurs, in part, because of protection by endogenous guanosine 3':5'-cyclic monophosphate (cyclic GMP). 2. Rat isolated hearts were subjected to 60 min left regional ischaemia followed by reperfusion (n = 10 per group). Methylene blue (20 microM), a soluble guanylate cyclase inhibitor, raised the incidence of reperfusion-induced ventricular fibrillation (VF) from 10% in control hearts to 80% (P < 0.05). This effect of methylene blue was abolished by co-perfusion with zaprinast (100 microM), a phosphodiesterase inhibitor which, in the rat heart, is cyclic GMP-specific (specific for the type-V phosphodiesterase isozyme). 3. Methylene blue reduced cyclic GMP levels in the ischaemic, non-ischaemic and reperfused myocardium (P < 0.05) to 50 +/- 10, 52 +/- 12 and 70 +/- 7 fmol mg-1 tissue wet weight, respectively from control values of 143 +/- 38, 147 +/- 43 and 156 +/- 15 fmol mg-1. Co-perfusion with zaprinast prevented this effect, and cyclic GMP levels were actually elevated (P < 0.05) to 366 +/- 102, 396 +/- 130 and 293 +/- 22 fmol mg-1 in ischaemic, non-ischaemic and reperfused myocardium, respectively. Zaprinast by itself also elevated cyclic GMP content. Cyclic AMP levels were not affected by zaprinast or methylene blue. 4. In conclusion, when endogenous cardiac cyclic GMP synthesis is reduced, susceptibility to reperfusion-induced VF after sustained ischaemia is substantially increased. The effect is prevented by inhibiting cyclic GMP degradation. Therefore cyclic GMP appears to be an endogenous intracellular cardioprotectant, and its actions may account for the low susceptibility to VF normally encountered in hearts reperfused after sustained ischaemia.

Animals↗
PubMed1995

Essential role for nitric oxide in neurogenic inflammation in rat cutaneous microcirculation. Evidence for an endothelium-independent mechanism.

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)

Animals↗
PubMed1994

Augmented antinociception following 7-nitro indazole and flurbiprofen in the conscious mouse.

Co-administration of the nitric oxide synthase inhibitor, 7-nitro indazole (1 mg/kg i.p.), with the cyclooxygenase inhibitor, flurbiprofen (5-75 mg/kg i.p.), resulted in significantly enhanced antinociceptive activity in mice (formalin-induced hindpaw licking assay) without affecting hindpaw inflammation. No antinociception was observed in animals pretreated with 7-nitro indazole (1 mg/kg i.p.) and flurbiprofen (100 micrograms subplantar). Flurbiprofen (50 mg/kg i.p.) pretreatment did not influence the inhibition of cerebellar or spinal cord nitric oxide synthase activity observed after 7-nitro indazole (1 or 25 mg/kg i.p.) administration and did not alter blood pressure in anaesthetised animals. Thus, flurbiprofen acts by a mechanism unrelated to a local anti-inflammatory effect in the hindpaw. Since nitric oxide synthase inhibitors are antinociceptive by an effect in the spinal cord (dorsal horn) this would appear to be a likely location for the nitric oxide synthase and cyclooxygenase enzymes targetted by 7-nitro indazole and flurbiprofen respectively.

Amino Acid Oxidoreductases↗
PubMed1994

Time course of inhibition of brain nitric oxide synthase by 7-nitro indazole.

7-Nitro indazole (7-NI) inhibits rat striatal, cerebellar, hippocampal, cerebral cortex and olfactory bulb nitric oxide synthase (NOS) in vitro with IC50 values of 0.68 +/- 0.01 microM, 0.64 +/- 0.03 microM, 1.53 +/- 0.05 microM, 0.93 +/- 0.04 microM and 1.05 +/- 0.02 microM respectively (n = 6). Intraperitoneal (i.p.) or oral administration of 7-NI (30 mg kg-1) to rats inhibited NOS enzyme activity measured ex vivo in all five brain regions (n = 5-6). NOS inhibition (maximal effect, 0.5 h post-injection) was transient with complete recovery at either 4 h (oral administration) or 24 h (i.p. administration). Repeated i.p. injection of 7-NI (30 mg kg-1, every 4 h for 20 h) inhibited NOS enzyme activity at 24 h by 51-61% in all brain regions. The relatively transient NOS inhibitory effect of 7-NI following parenteral administration should be taken into account when using this drug to evaluate the central effects of nitric oxide.

Administration, Oral↗
PubMed1994

Effect of 7-nitro indazole on neurotransmission in the rat vas deferens: mechanisms unrelated to inhibition of nitric oxide synthase.

1. The effect of the nitric oxide synthase (NOS) inhibitor, 7-nitro indazole (7-NI), on sympathetic and purinergic neurotransmission in the rat isolated vas deferens preparation has been studied. 2. 7-NI (50-200 microM) caused a dose- and frequency-dependent inhibition of the phasic (predominantly purinergic) contractile response of the rat vas deferens to electrical (field) stimulation (100 V, 0.5 ms). Greatest inhibition occurred at lower frequencies of stimulation (0.1-10 Hz). The sustained tonic contractile response (predominantly noradrenergic) was inhibited only at a high frequency of stimulation (60 Hz) and only at the highest concentration of 7-NI studies (200 microM). 3. 7-NI (100 microM) significantly reduced the contractile response of the vas deferens to exogenous ATP (20 microM-5 mM) and the stable P2X purinoceptor agonist, alpha, beta-methylene ATP (2.5 and 25.0 microM) but was without effect on contractions due to noradrenaline (0.1-50 microM) indicating a lack of antagonist effect on post-junctional alpha 1 adrenoceptors. 4. The effect of 7-NI (100 microM) on the phasic contractile response to field stimulation (0.1 and 2.0 Hz) was unaffected by preincubation of preparations with yohimbine (1.0 microM) or propranolol (0.01-10.0 microM) indicating the absence of involvement of alpha 2- or beta-adrenoceptors in this response. 5. 7-NI (50-600 microM) caused dose-related inhibition of contractions elicited by addition of a depolarizing concentration of KCl (64 mM). 6. The effect of 7-NI (100 microM) on the phasic contractile response to field stimulation (0.1 and 2.0 Hz) was unaffected by preincubation of preparations with L-arginine (1 mM). Neither L-arginine (1 mM) nor NC nitro L-arginine methyl ester (L-NAME, 100 LM) affected the response of the vas deferens to field stimulation at 0.1 or 2.0 Hz. Nitric oxide synthase (NOS) enzyme activity, measured as the conversion of[3H]-L-arginine to [3H]-citrulline, was not detectable in rat vas deferens homogenates.7. 7-Nr preferentially inhibits the purinergic component of the response of the rat vas deferens to field stimulation. The mechanism of action of 7-NI is not known but is not related to NOS inhibition. It seems likely that 7-NI combines an antagonist action at smooth muscle cell P2X-purinoceptors with the ability to inhibit the cellular influx of calcium ions. Although these hitherto unrecorded effects of 7-NI occur at relatively high concentrations, the effects described may contribute to the pharmacological effects of this NOS inhibitor.

Adenosine Triphosphate↗
PubMed1993

L-NG-nitro arginine p-nitroanilide (L-NAPNA) is anti-nociceptive in the mouse.

L-NG-nitro arginine p-nitroanilide (L-NAPNA), L-NG nitro arginine methyl ester (L-NAME) and L-NG-monomethyl arginine (L-NMMA) inhibit rat cerebellar nitric oxide synthase (NOS) with IC50s of 1.4 +/- 0.1 microM, 0.81 +/- 0.16 microM and 5.1 +/- 0.07 microM respectively. L-NAPNA inhibits the late phase of formalin-induced hindpaw licking (ED50, 57.2 mg kg-1) and acetic acid induced abdominal constrictions (ED50, 25 mg kg-1) in the mouse. L-NAPNA is approximately 65 times less active than L-NAME as an inhibitor of endothelium-dependent relaxation in the rabbit aorta and about 10 fold less potent as a vasopressor in the anaesthetized mouse. LNAPNA shows some degree of selectivity for the central NOS isoform and may be of clinical interest for the treatment of pain.

Amino Acid Oxidoreductases↗
PubMed1993

7-Nitro indazole, an inhibitor of nitric oxide synthase, exhibits anti-nociceptive activity in the mouse without increasing blood pressure.

7-Nitro indazole (7-NI) inhibits mouse cerebellar nitric oxide synthase (NOS) in vitro with an IC50 of 0.47 microM. Following i.p. administration in mice, 7-NI (10-50 mg kg-1) produces dose-related anti-nociception as evidenced by an inhibition of late phase (15-30 min) but not early phase (0-5 min) hindpaw licking time following subplantar injection of formalin (10 microliters, 5% v/v). The ED50 for this effect was 26 mg kg-1 (equivalent to 159.5 mumol kg-1). Similar i.p. administration of 7-NI (20 and 80 mg kg-1) in urethane-anaesthetized mice failed to increase MAP. Thus, 7-NI is a novel inhibitor of NOS which exhibits selectivity for the brain enzyme. Accordingly, 7-NI may be a useful starting point for the development of selective, centrally acting NOS inhibitors devoid of cardiovascular side effects and as a tool to study the central pharmacological effects of nitric oxide (NO).

Amino Acid Oxidoreductases↗
PubMed1993

Characterization of the novel nitric oxide synthase inhibitor 7-nitro indazole and related indazoles: antinociceptive and cardiovascular effects.

1. 7-Nitro indazole (7-NI, 10-50 mg kg-1), 6-nitro indazole and indazole (25-100 mg kg-1) administered i.p. in the mouse produce dose-related antinociception in the late phase of the formalin-induced hindpaw licking and acetic acid-induced abdominal constriction assays. The ED50 values (mg kg-1) were as follows: 7-NI (27.5 and 22.5), 6-nitro indazole (62.5 and 44.0) and indazole (41.0 and 48.5) in the two assays respectively. 3-Indazolinone, 6 amino indazole and 6-sulphanilimido indazole (all 50 mg kg-1) were without effect. With the exception of 5-nitro indazole (50 mg kg-1) which produced sedation, none of the other indazole derivates examined caused overt behavioural changes. 2. The antinociceptive effect of 7-NI (25 mg kg-1, i.p.) in the late phase of the formalin-induced hindpaw licking assay was partially (46.7 +/- 16.2%, n = 18) reversed by pretreatment with L- but not D-arginine (both 50 mg kg-1, i.p.). 3. The time course of 7-NI induced antinociception in the mouse was correlated with inhibition of brain (cerebellum) nitric oxide synthase (NOS) activity. Maximum antinociceptive activity and NOS inhibition was detected 18-30 min following i.p. administration. In contrast, no antinociceptive effect or inhibition of cerebellar NOS was detected 75 min post-injection. 4. 7-NI, 6-nitro indazole, indazole, 3-indazolinone and 6-amino indazole (all 50 mg kg-1) failed to influence mean arterial pressure (MAP) over the 45 min after i.p. administration in the anaesthetized mouse. Similarly, 7-NI (25 mg kg-1) administered i.v. in the anaesthetized rat did not increase MAP or influence the vasodepressor effect of i.v. injected acetylcholine (ACh) over the same period.5. 7-NI (100 microM) did not influence the vasorelaxant effect of ACh (IC50, 0.2 +/- 0.04 microM, cf. 0.16+/-0.06 microM, n = 6) in phenylephrine-precontracted rabbit aortic rings.6. These data provide further evidence that antinociception following administration of 7-NI in the mouse results from inhibition of central NOS activity and is not associated with inhibition of in vivo vascular endothelial cells NOS. Accordingly, 7-NI (or a derivative thereof) may provide an alternative approach to the development of novel antinociceptive drugs.

Amino Acid Oxidoreductases↗
PubMed1993

Inhibition of rat cerebellar nitric oxide synthase by 7-nitro indazole and related substituted indazoles.

1. 7-Nitro indazole (7-NI) produces potent inhibition of rat cerebellar nitric oxide synthase (NOS) with an IC50 of 0.9 +/- 0.1 microM (n = 6). NOS activity is dependent on the presence of both exogenous CaCl2 and NADPH. The inhibitory potency of 7-NI remained unaltered in the presence of different concentrations of either CaCl2 (0.75-7.5 mM) or NADPH (0.05-5.0 mM). 2. Kinetic (Lineweaver-Burke) analysis of the effect of 7-NI on rat cerebellar NOS revealed that inhibition was of a competitive nature with a Ki value of 5.6 microM. The Km of of cerebellar NOS with respect to L-arginine was 2.5 microM. 3. The following indazole derivatives (IC50 values shown in parentheses, all n = 6) caused concentration-related inhibition of rat cerebellar NOS in vitro: 6-nitro indazole (31.6 +/- 3.4 microM), 5-nitro indazole (47.3 +/- 2.3 microM), 3-chloro indazole (100.0 +/- 5.5 microM), 3-chloro 5-nitro indazole (158.4 +/- 2.1 microM) and indazole (177.8 +/- 2.1 microM). The IC50 values for 5-amino indazole, 6-amino indazole and 6-sulphanilimido indazole were in excess of 1 mM; 3-indazolinone was inactive. 4. 7-NI (10 mg kg-1) administered i.p. to rats produced 60 min thereafter a significant inhibition of NOS activity in cerebellum (31.1 +/- 3.2%, n = 6), cerebral cortex (38.2 +/- 5.6%, n = 6), hippocampus (37.0 +/- 2.8%, n = 6) and adrenal gland (23.7 +/- 3.0%, n = 6). NOS activity in olfactory bulb and stomach fundus were unchanged. 5. These results indicate that 7-NI is a potent and competitive inhibitor of rat brain NOS in vitro and also inhibits NOS in different brain regions and in the adrenal gland in vivo. Inhibition of NOS is a characteristic property of the indazole nucleus. Nitration of the indazole ring at positions 5, 6 and 7 results in a graded increase in inhibitory potency. Indazole-based inhibitors of NOS may prove useful tools with which to evaluate the biological roles of nitric oxide in the central nervous system.

Adrenal Glands↗
PubMed1993

Anti-nociceptive activity of nitric oxide synthase inhibitors in the mouse: dissociation between the effect of L-NAME and L-NMMA.

The anti-nociceptive effect of selective inhibitors of nitric oxide synthase has been assessed in a formalin-induced paw-licking model in mice. L-NG-Nitro arginine methyl ester (L-NAME) but not L-NG-monomethyl arginine (L-NMMA) exhibited anti-nociceptive activity in both the early and late phases of paw licking following intraperitoneal administration. The effect on the late phase response was more pronounced. L-NAME (0.1-100 micrograms) and L-NG-nitro arginine base (L-NOARG; 10 micrograms) but not D-NAME (10 micrograms) were also anti-nociceptive following intracerebroventricular administration. L-NAME (10 micrograms) administered by this route did not influence locomotor activity. L-NMMA was inactive at doses up to 40 micrograms by this route. At higher doses (75-200 micrograms) L-NMMA produced a similar and non-dose related reduction in early/late phase paw-licking time. D-NMMA (100 micrograms) was inactive. The greater anti-nociceptive effect of L-NAME in this model accords with recently published biochemical data indicating that L-NAME is several orders of magnitude more potent than L-NMMA as an inhibitor of brain nitric oxide synthase. These data support the use of L-NAME as a selective tool to investigate the central pharmacological effects of nitric oxide.

Amino Acid Oxidoreductases↗