RESUMO
This study investigated the role of H1 and H2 receptors in anxiety and the retrieval of emotional memory using a Trial 1/Trial 2 (T1/T2) protocol in an elevated plus-maze (EPM). Tests were performed on 2 consecutive days, designated T1 and T2. Before T1, the mice received intraperitoneal injections of saline (SAL), 20 mg/kg zolantidine (ZOL, an H2 receptor antagonist), or 8.0 or 16 mg/kg chlorpheniramine (CPA, an H1 receptor antagonist). After 40 min, they were subjected to the EPM test. In T2 (24 h later), each group was subdivided into two additional groups, and the animals from each group were re-injected with SAL or one of the drugs. In T1, the Student t-test showed no difference between the SAL and ZOL or 8 mg/kg CPA groups with respect to the percentages of open arm entries (%OAE) and open arm time (%OAT). However, administration of CPA at the highest dose of 16 mg/kg decreased %OAE and %OAT, but not locomotor activity, indicating anxiogenic-like behavior. Emotional memory, as revealed by a reduction in open arm exploration between the two trials, was observed in all experimental groups, indicating that ZOL and 8 mg/kg CPA did not affect emotional memory, whereas CPA at the highest dose affected acquisition and consolidation, but not retrieval of memory. Taken together, these results suggest that H1 receptor, but not H2, is implicated in anxiety-like behavior and in emotional memory acquisition and consolidation deficits in mice subjected to EPM testing.
Assuntos
Animais , Masculino , Camundongos , Ansiedade/induzido quimicamente , Benzotiazóis/farmacologia , Clorfeniramina/farmacologia , Antagonistas dos Receptores Histamínicos H1/farmacologia , /farmacologia , Transtornos da Memória/induzido quimicamente , Fenoxipropanolaminas/farmacologia , Piperidinas/farmacologia , Receptores Histamínicos H1/efeitos dos fármacos , Aprendizagem em Labirinto , MicroinjeçõesRESUMO
This study investigated the role of H1 and H2 receptors in anxiety and the retrieval of emotional memory using a Trial 1/Trial 2 (T1/T2) protocol in an elevated plus-maze (EPM). Tests were performed on 2 consecutive days, designated T1 and T2. Before T1, the mice received intraperitoneal injections of saline (SAL), 20â mg/kg zolantidine (ZOL, an H2 receptor antagonist), or 8.0 or 16â mg/kg chlorpheniramine (CPA, an H1 receptor antagonist). After 40â min, they were subjected to the EPM test. In T2 (24â h later), each group was subdivided into two additional groups, and the animals from each group were re-injected with SAL or one of the drugs. In T1, the Student t-test showed no difference between the SAL and ZOL or 8â mg/kg CPA groups with respect to the percentages of open arm entries (%OAE) and open arm time (%OAT). However, administration of CPA at the highest dose of 16â mg/kg decreased %OAE and %OAT, but not locomotor activity, indicating anxiogenic-like behavior. Emotional memory, as revealed by a reduction in open arm exploration between the two trials, was observed in all experimental groups, indicating that ZOL and 8â mg/kg CPA did not affect emotional memory, whereas CPA at the highest dose affected acquisition and consolidation, but not retrieval of memory. Taken together, these results suggest that H1 receptor, but not H2, is implicated in anxiety-like behavior and in emotional memory acquisition and consolidation deficits in mice subjected to EPM testing.
Assuntos
Ansiedade/induzido quimicamente , Benzotiazóis/farmacologia , Clorfeniramina/farmacologia , Antagonistas dos Receptores Histamínicos H1/farmacologia , Antagonistas dos Receptores H2 da Histamina/farmacologia , Transtornos da Memória/induzido quimicamente , Fenoxipropanolaminas/farmacologia , Piperidinas/farmacologia , Receptores Histamínicos H1/efeitos dos fármacos , Animais , Masculino , Aprendizagem em Labirinto , Camundongos , MicroinjeçõesRESUMO
In this study we determine different signaling pathways involved in beta(3) adrenoceptor (beta(3)-AR) dependent frequency stimulation in isolated rodent atria. Promiscuous coupling between different G-proteins and beta(3)-AR could explain the multiple functional effects of beta(3)-AR stimulation. We examine the mechanisms and functional consequences of dual adenylate cyclase and guanylate cyclase pathways coupling to beta(3)-AR in isolated rodent atria. The beta(3)-AR selective agonists ZD 7114 and ICI 215001 stimulated in a dose-dependent manner the contraction frequency that significantly correlated with cyclic AMP (cAMP) accumulation. Inhibition of adenylate cyclase shifted the chronotropic effect to the right. On the other hand, the ZD 7114 activity on frequency was enhanced by the inhibition of nitric oxide synthase (NOS) and soluble guanylate cyclase. This countervailing negative chronotropic nitric oxide-cyclic GMP (NO-cGMP) significantly correlated with the increase on NOS activity and cGMP accumulation. Current analysis showed a negative cross talk between cAMP chronotropic and NO-cGMP effects by inhibition of phospholipase C (PLC), calcium/calmodulin (CaM), protein kinase C (PKC), NOS isoforms and Gi-protein on the effects of beta(3)-AR stimulation. RT-PCR detected both eNOS and nNOS in isolated rat atria. NOS isoforms performed independently. Only nNOS participated in limiting the effect of beta(3)-AR stimulation. In eNOS-KO (eNOS-/-) mice the chronotropic effect of beta(3)-AR agonists did not differ from wild type (WT) mice atria, but it was increased by the inhibition of nNOS activity. Our results suggest that the increase in frequency by beta(3)-AR activation on isolated rodent atria is associated to a parallel increases in cAMP. The nNOS-cGMP pathway negatively modulates beta(3)-AR activation. Multiple signal transduction pathways between G-protein and beta(3)-AR may protect myocardium from catecholamine-induced cardiotoxic effects.
Assuntos
GMP Cíclico/metabolismo , Frequência Cardíaca/fisiologia , Contração Miocárdica/fisiologia , Óxido Nítrico Sintase Tipo II/metabolismo , Óxido Nítrico/metabolismo , Receptores Adrenérgicos beta/metabolismo , Agonistas Adrenérgicos beta/farmacologia , Animais , Frequência Cardíaca/efeitos dos fármacos , Masculino , Camundongos , Camundongos Knockout , Contração Miocárdica/efeitos dos fármacos , Óxido Nítrico Sintase Tipo II/deficiência , Óxido Nítrico Sintase Tipo III , Fenoxiacetatos/farmacologia , Fenoxipropanolaminas/farmacologia , Ratos , Ratos Wistar , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologiaRESUMO
BACKGROUND: Evidences have shown that beta1 and beta2 adrenoceptors co-exist in human fibroblasts, but it is not yet clear the functional expression of beta3 adrenoceptor in these cells. The aim of this study was to investigate the expression and biological effect of beta3 adrenoceptor activation in human skin fibroblast and the different signaling pathways involved in its effect. METHODS: For this purpose in vitro cultures of human skin fibroblast were established from human foreskin and grown in Dulbecco's modified Eagle's medium. The effect of ZD 7114 (beta3 agonist) on cell DNA synthesis, radioligand binding assay, cyclic GMP and cyclic AMP accumulation and nitric oxide synthase (NOS) activity were evaluated. RESULTS: 3H-CGP binding to human fibroblast membranes was a saturable process to a single class of binding site. The equilibrium parameters were: Kd 20+/-3 pM and Bmax 222+/-19 fmol/mg protein. Ki values showed that these cells express a high number of beta(3)adrenoceptor subtypes. ZD 7114 stimulation of beta3 adrenoceptor exerts a concentration-dependent inhibition of DNA synthesis and cAMP accumulation with parallel increase in NOS activity that led to cGMP accumulation. All these effects were blocked by the beta3 adrenoceptor antagonist (SR 59230A). The effect of ZD 7114 on DNA synthesis significantly correlated with its action either on cAMP or NOS-cGMP signaling system. Inhibitors of NOS activity and NO-sensitive guanylate cyclase prevented the inhibitory effect of ZD 7114 on DNA synthesis. In addition, the beta3 adrenoceptor-dependent increase in cGMP and activation of NOS were blocked by the inhibition of phospholipase C (PLC), calcium/calmodulin (CaM), endothelial NOS activity and cGMP accumulation. CONCLUSIONS: beta3 adrenoceptor activation exerts inhibitory effect on human fibroblast DNA synthesis as a result of the activation of NO-cGMP pathway and the inhibition of adenylate cyclase activity. The mechanism appears to occurs secondarily to stimulation of PLC and CaM. This in turn triggers cascade reaction leading to increase production of NO-cGMP with decrease in cAMP accumulation.
Assuntos
GMP Cíclico/metabolismo , DNA/biossíntese , Fibroblastos/metabolismo , Óxido Nítrico/metabolismo , Receptores Adrenérgicos beta 3/metabolismo , Agonistas de Receptores Adrenérgicos beta 3 , Agonistas Adrenérgicos beta/farmacologia , Células Cultivadas , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Humanos , Masculino , Modelos Biológicos , Fenoxiacetatos/farmacologia , Fenoxipropanolaminas/farmacologia , Transdução de Sinais , Pele/citologia , Pele/metabolismoRESUMO
The chemical specificity for the beta-adrenoceptor mediated relaxation of rat esophageal smooth muscle was evaluated using selective and non-selective beta-adrenoceptor agonists and antagonists. Pindolol, ICI 89,406, ICI 118551 [erythro-1-(7-methylindan-4-yloxy)-3-(isopropylamine)-but an-2-ol] and the beta-adrenoceptor alkylating agent, pindobind, produced only small rightward shifts in the concentration-response curves of (-)-isoprenaline and (-)-trimetoquinol in this preparation. Rank order potency (pD2 values) of agonists was: (+/-)-trimetoquinol [1-(3',4',5'-trimethoxybenzyl)-6,7-dihydroxy-1,2,3, 4-tetrahydroisoquinoline] (8.34) = (-)-trimetoquinol (8.26) = BRL 37344 [(R* R*)-(+/-)-4-[2'-2-hydroxy 2-(3-chlorophenyl)ethylamino]propyl] phenoxyacetic acid] (8.16) = ICID7114 [(S)-4-(2-hydroxy- 3-phenoxy-propylamino-ethoxy)-N-(2-methoxyethyl) phenoxyacetamide] (8.03) > or = (-)-isoprenaline (7.82) > 3',5'-diiodotrimetoquinol [1-(3',5'-diiodo-4'-methoxybenzyl)-6, 7-dihydroxy-1,2,3,4-tetrahydroisoquinoline] (7.28) > 3'-iodotrimetoquinol [1-(3'-iodo-4',5'-dimethoxybenzyl)-6, 7-dihydroxy-1,2,3,4-tetrahydroisoquinoline] (7.04) > ractopamine (6.84) = 5,8-difluorotrimetoquinol [5,8-difluoro-6,7-dihydroxy-1- (3',4',5'-trimethoxybenzyl)-1,2,3,4-tetrahydroisoquinoline] (6.82) > 8-fluorotrimetoquinol [6,7-dihydroxy-8-fluoro-1-(3',4',5'- trimethoxybenzyl)-1,2,3,4-tetrahydroisoquinoline] (6.56) > or = (-)-noradrenaline (6.46) > or = (-)-adrenaline (6.36) > (+/-)-noradrenaline (6.24) > (+/-)-adrenaline (6.00) > clenbuterol (5.83) > (-)-1-benzyl-6, 7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (5.75). Isomeric activity ratios of trimetoquinol isomers [(-)-(S)- > > (+)-(R)-] in esophageal smooth muscle in the presence and absence of 1 microM pindolol were 1995- and 2951-fold, respectively; and were much greater than those in rat atria (282-fold) and rat trachea (107-fold). The atypical beta/beta 3-adrenoceptor partial agonist, ICI D7114, produced concentration-dependent rightward shifts of the concentration-response curves of (-)-isoprenaline, (-)-trimetoquinol and the reference atypical beta/beta 3-adrenoceptor agonist, BRL 37344. Schild plot analysis of ICI D7114 against trimetoquinol gave slope and pA2 values of 0.91 and of 7.9, respectively. These results clearly demonstrate that the relaxant effects of these agonists in rat esophageal smooth muscle are primarily mediated through the activation of atypical beta/beta 3-adrenoceptors. (-)-Trimetoquinol was as potent as (-)- isoprenaline and BRL 37344, and was the most stereoselective agonist evaluated in this tissue system.
Assuntos
Relaxamento Muscular/efeitos dos fármacos , Músculo Liso/fisiologia , Receptores Adrenérgicos beta/fisiologia , Antagonistas de Receptores Adrenérgicos beta 1 , Antagonistas de Receptores Adrenérgicos beta 2 , Antagonistas Adrenérgicos beta/farmacologia , Animais , Carbacol/farmacologia , Clembuterol/farmacologia , Monoterpenos Cicloexânicos , Esôfago/efeitos dos fármacos , Etanolaminas/farmacologia , Feminino , Átrios do Coração/efeitos dos fármacos , Técnicas In Vitro , Isoproterenol/farmacologia , Masculino , Músculo Liso/efeitos dos fármacos , Fenetilaminas/farmacologia , Fenoxiacetatos/farmacologia , Fenoxipropanolaminas , Pindolol/análogos & derivados , Pindolol/farmacologia , Propanolaminas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores Adrenérgicos beta/efeitos dos fármacos , Antagonistas da Serotonina/farmacologia , Traqueia/efeitos dos fármacos , Tretoquinol/análogos & derivados , Tretoquinol/farmacologiaRESUMO
The effects of the H1-receptor antagonist diphenhydramine and the brain-penetrating H2-receptor antagonist zolantidine were studied in rats implanted for chronic sleep recordings. Diphenhydramine (1.0-4.0 mg/kg) significantly increased slow wave sleep and decreased wakefulness. Zolantidine (0.25-8.0 mg/kg) had no significant effects on any of the sleep parameters examined. One possibility is that zolantidine did not enter the brain in sufficient concentration to produce significant changes on sleep and wakefulness. Another possibility is that blockade of H2-receptor involved parts of the brain other than those implicated in the sleep-wake cycle. The feasibility remains that H2-receptors are not involved in sleep regulation. The absence of selective, brain-penetrating H2-receptor agonists precludes a more detailed analysis of the role of this subtype of receptor in the control of sleep and wakefulness.