RESUMO
Flavonoid galetin 3,6-dimethyl ether (FGAL) has been isolated from the aerial parts of Piptadenia stipulaceae and has shown a spasmolytic effect in guinea pig ileum. Thus, we aimed to characterize its relaxant mechanism of action. FGAL exhibited a higher relaxant effect on ileum pre-contracted by histamine (EC50=1.9±0.4×10(-7) M) than by KCl (EC50=2.6±0.5×10(-6) M) or carbachol (EC50=1.8±0.4×10(-6) M). The flavonoid inhibited the cumulative contractions to histamine, as well as to CaCl2 in depolarizing medium nominally Ca(2+)-free. The flavonoid relaxed the ileum pre-contracted by S-(-)-Bay K8644 (EC50=9.5±1.9×10(-6) M) but less potently pre-contracted by KCl or histamine. CsCl attenuated the relaxant effect of FGAL (EC50=1.1±0.3×10(-6) M), but apamin or tetraethylammonium (1mM) had no effect (EC50=2.6±0.2×10(-7) and 1.6±0.3×10(-7) M, respectively), ruling out the involvement of small and big conductance Ca(2+)-activated K(+) channels (SKCa and BKCa, respectively). Either 4-aminopyridine or glibenclamide attenuated the relaxant effect of FGAL (EC50=1.8±0.2×10(-6) and 1.5±0.5×10(-6) M, respectively), indicating the involvement of voltage- and ATP-sensitive K(+) channels (KV and KATP, respectively). FGAL did not alter the viability of intestinal myocytes in the MTT assay and decreased (88%) Fluo-4 fluorescence, indicating a decrease in cytosolic Ca(2+) concentration. Therefore, the relaxant mechanism of FGAL involves pseudo-irreversible noncompetitive antagonism of histaminergic receptors, KV and KATP activation and blockade of CaV1, thus leading to a reduction in cytosolic Ca(2+) levels.
Assuntos
Cálcio/metabolismo , Flavonoides/farmacologia , Íleo/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Canais de Potássio/agonistas , Éster Metílico do Ácido 3-Piridinacarboxílico, 1,4-Di-Hidro-2,6-Dimetil-5-Nitro-4-(2-(Trifluormetil)fenil)/farmacologia , 4-Aminopiridina/farmacologia , Animais , Apamina/farmacologia , Cloreto de Cálcio/antagonistas & inibidores , Cloreto de Cálcio/farmacologia , Carbacol/antagonistas & inibidores , Carbacol/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Césio/farmacologia , Cloretos/farmacologia , Flavonoides/antagonistas & inibidores , Glibureto/farmacologia , Cobaias , Histamina/farmacologia , Antagonistas dos Receptores Histamínicos/farmacologia , Íleo/fisiologia , Células Musculares/efeitos dos fármacos , Bloqueadores dos Canais de Potássio/farmacologia , Cloreto de Potássio/antagonistas & inibidores , Cloreto de Potássio/farmacologia , TetraetilamônioRESUMO
The present study deals with the pharmacological effects of the sesquiterpene alcohol (-)-α-bisabolol on various smooth-muscle preparations from rats. Under resting tonus, (-)-α-bisabolol (30-300 µmol/L) relaxed duodenal strips, whereas it showed biphasic effects in other preparations, contracting endothelium-intact aortic rings and urinary bladder strips, and relaxing these tissues at higher concentrations (600-1000 µmol/L). In preparations precontracted either electromechanically (by 60 mmol/L K(+)) or pharmacomechanically (by phenylephrine or carbachol), (-)-α-bisabolol showed only relaxing properties. The pharmacological potency of (-)-α-bisabolol was variable, being higher in mesenteric vessels, whereas it exerted relaxing activity with a lesser potency on tracheal or colonic tissues. In tissues possessing spontaneous activity, (-)-α-bisabolol completely decreased spontaneous contractions in duodenum, whereas it increased their amplitude in urinary bladder tissue. Administered in vivo, (-)-α-bisabolol attenuated the increased responses of carbachol in tracheal rings of ovalbumin-sensitized rats challenged with ovalbumin, but was without effect in the decreased responsiveness of urinary bladder strips in mice treated with ifosfamide. In summary, (-)-α-bisabolol is biologically active in smooth muscle. In some tissues, (-)-α-bisabolol preferentially relaxed contractions induced electromechanically, especially in tracheal smooth muscle. The findings from tracheal rings reveal that (-)-α-bisabolol may be an inhibitor of voltage-dependent Ca(2+) channels.
Assuntos
Contração Muscular/efeitos dos fármacos , Relaxamento Muscular/efeitos dos fármacos , Músculo Liso/efeitos dos fármacos , Sesquiterpenos/farmacologia , Animais , Carbacol/antagonistas & inibidores , Carbacol/farmacologia , Cistite/induzido quimicamente , Cistite/tratamento farmacológico , Modelos Animais de Doenças , Duodeno/efeitos dos fármacos , Duodeno/fisiologia , Ifosfamida , Técnicas In Vitro , Inflamação/induzido quimicamente , Inflamação/tratamento farmacológico , Masculino , Sesquiterpenos Monocíclicos , Contração Muscular/fisiologia , Relaxamento Muscular/fisiologia , Músculo Liso/fisiologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/fisiologia , Ovalbumina , Fenilefrina/farmacologia , Ratos , Ratos Wistar , Traqueia/efeitos dos fármacos , Traqueia/fisiologia , Bexiga Urinária/efeitos dos fármacos , Bexiga Urinária/fisiologiaRESUMO
Inhibition of type-5 phosphodiesterase by sildenafil decreases capacitative Ca2+ entry mediated by transient receptor potential proteins (TRPs) in the pulmonary artery. These families of channels, especially the canonical TRP (TRPC) subfamily, may be involved in the development of bronchial hyperresponsiveness, a hallmark of asthma. In the present study, we evaluated i) the effects of sildenafil on tracheal rings of rats subjected to antigen challenge, ii) whether the extent of TRPC gene expression may be modified by antigen challenge, and iii) whether inhibition of type-5 phosphodiesterase (PDE5) may alter TRPC gene expression after antigen challenge. Sildenafil (0.1 µM to 0.6 mM) fully relaxed carbachol-induced contractions in isolated tracheal rings prepared from naive male Wistar rats (250-300 g) by activating the NO-cGMP-K+ channel pathway. Rats sensitized to antigen by intraperitoneal injections of ovalbumin were subjected to antigen challenge by ovalbumin inhalation, and their tracheal rings were used to study the effects of sildenafil, which more effectively inhibited contractions induced by either carbachol (10 µM) or extracellular Ca2+ restoration after thapsigargin (1 µM) treatment. Antigen challenge increased the expression of the TRPC1 and TRPC4 genes but not the expression of the TRPC5 and TRPC6 genes. Applied before the antigen challenge, sildenafil increased the gene expression, which was evaluated by RT-PCR, of TRPC1 and TRPC6, decreased TRPC5 expression, and was inert against TRPC4. Thus, we conclude that PDE5 inhibition is involved in the development of an airway hyperresponsive phenotype in rats after antigen challenge by altering TRPC gene expression.
Assuntos
Animais , Masculino , Ratos , Canais de Cálcio/efeitos dos fármacos , Carbacol/farmacologia , Piperazinas/farmacologia , Sulfonas/farmacologia , Canais de Cátion TRPC/efeitos dos fármacos , Traqueia/efeitos dos fármacos , Vasodilatadores/farmacologia , Canais de Cálcio/metabolismo , Carbacol/antagonistas & inibidores , Expressão Gênica , Lactonas/farmacologia , Contração Muscular/efeitos dos fármacos , Contração Muscular/fisiologia , Óxido Nítrico/metabolismo , Ovalbumina/farmacologia , Purinas/farmacologia , Ratos Wistar , Sesquiterpenos/farmacologia , Canais de Cátion TRPC/genética , Canais de Cátion TRPC/metabolismo , Traqueia/metabolismo , Traqueia/fisiopatologiaRESUMO
Inhibition of type-5 phosphodiesterase by sildenafil decreases capacitative Ca2+ entry mediated by transient receptor potential proteins (TRPs) in the pulmonary artery. These families of channels, especially the canonical TRP (TRPC) subfamily, may be involved in the development of bronchial hyperresponsiveness, a hallmark of asthma. In the present study, we evaluated i) the effects of sildenafil on tracheal rings of rats subjected to antigen challenge, ii) whether the extent of TRPC gene expression may be modified by antigen challenge, and iii) whether inhibition of type-5 phosphodiesterase (PDE5) may alter TRPC gene expression after antigen challenge. Sildenafil (0.1 µM to 0.6 mM) fully relaxed carbachol-induced contractions in isolated tracheal rings prepared from naive male Wistar rats (250-300 g) by activating the NO-cGMP-K+ channel pathway. Rats sensitized to antigen by intraperitoneal injections of ovalbumin were subjected to antigen challenge by ovalbumin inhalation, and their tracheal rings were used to study the effects of sildenafil, which more effectively inhibited contractions induced by either carbachol (10 µM) or extracellular Ca2+ restoration after thapsigargin (1 µM) treatment. Antigen challenge increased the expression of the TRPC1 and TRPC4 genes but not the expression of the TRPC5 and TRPC6 genes. Applied before the antigen challenge, sildenafil increased the gene expression, which was evaluated by RT-PCR, of TRPC1 and TRPC6, decreased TRPC5 expression, and was inert against TRPC4. Thus, we conclude that PDE5 inhibition is involved in the development of an airway hyperresponsive phenotype in rats after antigen challenge by altering TRPC gene expression.
Assuntos
Canais de Cálcio/efeitos dos fármacos , Carbacol/farmacologia , Piperazinas/farmacologia , Sulfonas/farmacologia , Canais de Cátion TRPC/efeitos dos fármacos , Traqueia/efeitos dos fármacos , Vasodilatadores/farmacologia , Animais , Canais de Cálcio/metabolismo , Carbacol/antagonistas & inibidores , Expressão Gênica , Lactonas/farmacologia , Masculino , Contração Muscular/efeitos dos fármacos , Contração Muscular/fisiologia , Óxido Nítrico/metabolismo , Ovalbumina/farmacologia , Purinas/farmacologia , Ratos , Ratos Wistar , Sesquiterpenos/farmacologia , Citrato de Sildenafila , Canais de Cátion TRPC/genética , Canais de Cátion TRPC/metabolismo , Traqueia/metabolismo , Traqueia/fisiopatologiaRESUMO
In the present study, we report that low concentrations of the glutamate ionotropic agonist kainate decreased the turnover of [3H]-phosphoinositides ([3H]-InsPs) induced by muscarinic receptors in the chick embryonic retina. When 100 microM carbachol was used, the estimated IC50 value for kainate was 0.2 microM and the maximal inhibition of approximately 50% was obtained with 1 microM or higher concentrations of the glutamatergic agonist. Our data also show that veratridine, a neurotoxin that increases the permeability of voltage-sensitive sodium channels, had no effect on [3H]-InsPs levels of the embryonic retina. However, 50 microM veratridine, but not 50 mM KCl, inhibited approximately 65% of the retinal response to carbachol. While carbachol increased [3H]-InsPs levels from 241.2 +/- 38.0 to 2044.5 +/- 299.9 cpm/mg protein, retinal response decreased to 861.6 +/- 113.9 cpm/mg protein when tissues were incubated with carbachol plus veratridine. These results suggest that the accumulation of phosphoinositides induced by activation of muscarinic receptors can be inhibited by the influx of Na+ ions triggered by activation of kainate receptors or opening of voltage-sensitive sodium channels in the chick embryonic retina.
Assuntos
Carbacol/antagonistas & inibidores , Agonistas de Aminoácidos Excitatórios/farmacologia , Ácido Caínico/farmacologia , Agonistas Muscarínicos/farmacologia , Fosfatidilinositóis/metabolismo , Receptores Muscarínicos/metabolismo , Retina/embriologia , Retina/metabolismo , Veratridina/farmacologia , Animais , Embrião de Galinha , Agonistas de Aminoácidos Excitatórios/metabolismo , Ácido Glutâmico/farmacologia , Ácido Caínico/metabolismo , Cloreto de Potássio , Receptores Muscarínicos/efeitos dos fármacos , Retina/efeitos dos fármacos , Canais de SódioRESUMO
We determined the effect of intracerebroventricular (icv) administration of losartan, an angiotensin II (ANG II) subtype 1 receptor (AT1) antagonist, on icv carbachol-induced natriuresis, kaliuresis and antidiuresis in water-loaded male Holtzman rats (250-300 g) with a cannula implanted into the lateral ventricle (LV). The rats were water loaded with 5% of their body weight by gavage twice, with the second gavage one hour after the first. Carbachol (2 nmol in 1 microliter) was injected icv immediately after the second load. When losartan (DUP-753, 50 nmol in 1 microliter) was administered icv, it was given 3 min before carbachol. Previous icv treatment with losartan significantly reduced the icv carbachol-induced natriuresis (324 +/- 17 microEq/120 min), kaliuresis (103 +/- 15 microEq/120 min) and antidiuresis (13.5 +/- 2.1 ml/120 min) compared to the effects of previous icv injection of saline (Na+ excretion = 498 +/- 22 microEq/120 min; K+ excretion = 167 +/- 20 microEq/120 min; urine volume = 5.2 +/- 1.2 ml/120 min). These results, reported as means +/- SEM for 12 rats in each group, are consistent with the hypothesis that AT1 subtype receptors participate in the regulation of body electrolyte balance.
Assuntos
Antagonistas de Receptores de Angiotensina , Compostos de Bifenilo/farmacologia , Carbacol/antagonistas & inibidores , Diurese/efeitos dos fármacos , Imidazóis/farmacologia , Natriurese/efeitos dos fármacos , Potássio/urina , Tetrazóis/farmacologia , Animais , Carbacol/administração & dosagem , Ingestão de Líquidos , Injeções Intraventriculares , Losartan , Masculino , Ratos , Ratos Sprague-DawleyRESUMO
In the present study, we investigated the effect of previous injection of either prazosin (alpha 1-adrenergic antagonist) or atropine (muscarinic cholinergic antagonist) into the medial septal area (MSA) on the pressor and dipsogenic response induced by intracerebroventricular (ICV) injection of carbachol (cholinergic agonist) and angiotensin II (ANGII) in rats. The pressor and dipsogenic responses to ICV carbachol (7 nmol) were reduced after previous treatment of the MSA with atropine (0.5 to 5 nmol), but not prazosin (20 and 40 nmol). The dipsogenic response to ICA ANGII (25 ng) was reduced after prazosin (40 nmol) into the MSA. The pressor response to ICV ANGII was not changed either by previous treatment of the MSA with prazosin or atropine. The present results suggest a dissociation among the pathways subserving the control of dipsogenic and pressor responses to central cholinergic or angiotensinergic activation.
Assuntos
Angiotensina II/farmacologia , Vias Autônomas/fisiologia , Pressão Sanguínea/efeitos dos fármacos , Carbacol/farmacologia , Ingestão de Líquidos/efeitos dos fármacos , Sistema Nervoso Parassimpático/fisiologia , Sistema Nervoso Simpático/fisiologia , Angiotensina II/administração & dosagem , Angiotensina II/antagonistas & inibidores , Animais , Atropina/farmacologia , Encéfalo/anatomia & histologia , Encéfalo/fisiologia , Carbacol/administração & dosagem , Carbacol/antagonistas & inibidores , Injeções Intraventriculares , Masculino , Prazosina/farmacologia , RatosRESUMO
The changes in tail-flick latency (TFL) to noxious heating of the skin produced by the microinjection of carbachol (CCh) into the dorsal (dPAG), lateral (lPAG), and ventral (vPAG) portions of the mesencephalic periaqueductal gray matter (PAG) were studied in the rat. A significant increase in TFL was produced by CCh (0.2 microgram/0.5 microliter) microinjected into sites widely distributed within the PAG. The effect of CCh was stronger in the most caudal portion of the DPAG. Smaller effects were obtained after injection of CCh into the aqueduct, indicating that drug diffusion from the injection sites to the aqueduct lumen is unlikely to cause the antinociceptive effect of CCh. Dimethyl-phenyl-piperazinium (0.35 microgram/0.5 microliter), but not bethanechol (0.22 and 0.44 microgram/0.5 microliter), produced effects similar to CCh (0.2 microgram/0.5 microliter), when injected into the dPAG. The effects of CCh were inhibited by the previous administration of mecamylamine (1 microgram/0.5 microliter), but not atropine (1 microgram/0.5 microliter) or naloxone (1 microgram/0.5 microliter), into the dPAG. These results are indicative that antinociception produced by CCh from the dPAG depends on nicotinic, but not muscarinic or opioid mechanisms within the dPAG. The intraperitoneal administration of phenoxybenzamine (1 mg/kg) or mecamylamine (1 mg/kg), but not naloxone (1 mg/kg), methysergide (1 mg/kg), or atropine (1 mg/kg), inhibited the effects of CCh injected into the dPAG. In contrast, a higher dose of intraperitoneal phenoxybenzamine (5 mg/kg) was ineffective against the antinociception evoked by CCh when injected into the vPAG. Therefore, the effects of CCh from the dPAG may depend on the activation of centrifugal pathways involving both nicotinic and alpha-adrenergic mechanisms. In addition, the results indicate that different cholinergic substrates in the PAG may mediate both alpha-adrenergic and non-alpha-adrenergic descending pain mechanisms activated by the dPAG and vPAG, respectively.
Assuntos
Analgésicos/farmacologia , Carbacol/farmacologia , Mesencéfalo/fisiologia , Substância Cinzenta Periaquedutal/fisiologia , Analgésicos/administração & dosagem , Analgésicos/antagonistas & inibidores , Animais , Betanecol/farmacologia , Mapeamento Encefálico , Carbacol/administração & dosagem , Carbacol/antagonistas & inibidores , Iodeto de Dimetilfenilpiperazina/farmacologia , Injeções Intraperitoneais , Masculino , Mesencéfalo/anatomia & histologia , Metisergida/farmacologia , Microinjeções , Naloxona/farmacologia , Medição da Dor/efeitos dos fármacos , Substância Cinzenta Periaquedutal/anatomia & histologia , Fenoxibenzamina/farmacologia , Ratos , Ratos Wistar , Temperatura Cutânea/efeitos dos fármacosRESUMO
The present study was performed to investigate the effect of treatment with furosemide on the pressor response induced by intracerebroventricular (i.c.v.) injections of cholinergic (carbachol) and adrenergic (norepinephrine) agonists, angiotensin II (ANGII) and hypertonic saline (HS, 2 M NaCl). The changes induced by furosemide treatment on the pressor response to intravenous (i.v.) norepinephrine, ANGII and arginine vasopressin (AVP) were also studied. Rats with a stainless-steel cannula implanted into the lateral ventricle (LV) were used. Two injections of furosemide (30 mg/kg b.wt. each) were performed 12 and 1 h before the experiments. Treatment with furosemide reduced the pressor response induced by carbachol, norepinephrine and ANGII i.c.v., but no change was observed in the pressor response to i.c.v. 2 M NaCl. The pressor response to i.v. ANGII and norepinephrine, but not AVP, was also reduced after treatment with furosemide. These results show that the treatment with furosemide impairs the pressor responses induced by central or peripheral administration of adrenergic agonist or ANGII, as well as those induced by central cholinergic activation. The results suggest that the treatment with furosemide impairs central and peripheral pressor responses mediated by sympathetic activation and ANGII, but not those produced by AVP.
Assuntos
Angiotensina II/antagonistas & inibidores , Arginina Vasopressina/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Carbacol/antagonistas & inibidores , Furosemida/farmacologia , Norepinefrina/antagonistas & inibidores , Solução Salina Hipertônica/farmacologia , Vasoconstrição/efeitos dos fármacos , Animais , Arginina Vasopressina/administração & dosagem , Carbacol/administração & dosagem , Injeções Intravenosas , Injeções Intraventriculares , Masculino , Norepinefrina/administração & dosagem , Ratos , Solução Salina Hipertônica/administração & dosagemRESUMO
The microinjection of carbachol into the medial preoptic area (MPO) of the rat induced natriuresis, kaliuresis and anti-diuresis in a dose-related manner. Atropine blocked all responses to carbachol. Hexamethonium impaired the dose-response effect of carbachol on kaliuresis, but had no effect on natriuresis and enhanced the antidiuretic effect of carbachol. Nicotine alone had no effects, but pre-treatment with nicotine enhanced the responses to carbachol. These data show that activity of the muscarinic receptors of the MPO increases renal electrolyte and reduces water excretion. They also suggest that nicotinic receptors have an inhibitory effect on water excretion. Nicotine could act through mechanisms unrelated to nicotinic receptors to enhance the effect of the carbachol.
Assuntos
Carbacol/farmacologia , Potássio/urina , Área Pré-Óptica/efeitos dos fármacos , Sódio/urina , Animais , Atropina/farmacologia , Carbacol/antagonistas & inibidores , Relação Dose-Resposta a Droga , Compostos de Hexametônio/farmacologia , Masculino , Nicotina/farmacologia , Ratos , Água/metabolismoRESUMO
The effect of atropine injection into the medial septal area (MSA) or medial preoptic area (MPOA) on carbachol-induced drinking was evaluated in conscious unrestrained rats during a food-associated drinking test reinforced by 14 h of food deprivation. Atropine did not alter food intake when injected into either area, nor did it affect drinking after its injection into the MPOA. However, atropine markedly reduced water intake after its injection into the MSA. These results suggest that the central cholinergic system in the MSA can participate in the regulation of food-associated drinking
Assuntos
Ratos , Animais , Masculino , Atropina/farmacologia , Carbacol/antagonistas & inibidores , Ingestão de Líquidos/efeitos dos fármacos , Área Pré-Óptica/efeitos dos fármacos , Núcleos Septais/efeitos dos fármacos , Atropina/administração & dosagem , Ingestão de Alimentos/efeitos dos fármacos , Privação de Alimentos , Ratos EndogâmicosRESUMO
The effect of atropine injection into the medial septal area (MSA) or medial preoptic area (MPOA) on carbachol-induced drinking was evaluated in conscious unrestrained rats during a food-associated drinking test reinforced by 14 h of food deprivation. Atropine did not alter food intake when injected into either area, nor did it affect drinking after its injection into the MPOA. However, atropine markedly reduced water intake after its injection into the MSA. These results suggest that the central cholinergic system in the MSA can participate in the regulation of food-associated drinking.