RESUMO
Congenital myasthenic syndromes (CMS) result from reduced cholinergic transmission at neuromuscular junctions (NMJs). While the etiology of CMS varies, the disease is characterized by muscle weakness. To date, it remains unknown if CMS causes long-term and irreversible changes to skeletal muscles. In this study, we examined skeletal muscles in a mouse line with reduced expression of Vesicular Acetylcholine Transporter (VAChT, mouse line herein called VAChT-KDHOM). We examined this mouse line for several reasons. First, VAChT plays a central function in loading acetylcholine (ACh) into synaptic vesicles and releasing it at NMJs, in addition to other cholinergic nerve endings. Second, loss of function mutations in VAChT causes myasthenia in humans. Importantly, VAChT-KDHOM present with reduced ACh and muscle weakness, resembling CMS. We evaluated the morphology, fiber type (myosin heavy chain isoforms), and expression of muscle-related genes in the extensor digitorum longus (EDL) and soleus muscles. This analysis revealed that while muscle fibers atrophy in the EDL, they hypertrophy in the soleus muscle of VAChT-KDHOM mice. Along with these cellular changes, skeletal muscles exhibit altered levels of markers for myogenesis (Pax-7, Myogenin, and MyoD), oxidative metabolism (PGC1-α and MTND1), and protein degradation (Atrogin1 and MuRF1) in VAChT-KDHOM mice. Importantly, we demonstrate that deleterious changes in skeletal muscles and motor deficits can be partially reversed following the administration of the cholinesterase inhibitor, pyridostigmine in VAChT-KDHOM mice. These findings reveal that fast and slow type muscles differentially respond to cholinergic deficits. Additionally, this study shows that the adverse effects of cholinergic transmission, as in the case of CMS, on fast and slow type skeletal muscles are reversible.
Assuntos
Acetilcolina/metabolismo , Músculo Esquelético/metabolismo , Síndromes Miastênicas Congênitas/metabolismo , Vesículas Sinápticas/metabolismo , Acetilcolina/antagonistas & inibidores , Animais , Modelos Animais de Doenças , Camundongos Transgênicos , Músculo Esquelético/efeitos dos fármacos , Síndromes Miastênicas Congênitas/genética , Junção Neuromuscular/metabolismo , Proteínas Vesiculares de Transporte de Acetilcolina/metabolismoRESUMO
The aim of this work is to determine whether consuming tap water containing arsenic (20 microg/L) alters oxidative stress levels in female rats and changes vascular response. Whereas nitric oxide produces complete relaxation, arsenic (7 months of exposure) impairs the acetylcholine-induced endothelial relaxation in the rat aorta compared with control rats. Arsenic exposure results in a marked elevation in reactive oxygen species in blood, and delta-aminolevulinic acid dehydratase activity, which is a sensitive biomarker for arsenic toxicity and oxidative stress, is significantly decreased in erythrocytes from 7-month-old rats. Diastolic blood pressure increases significantly in 7-month-old arsenic-treated versus control rats. The percentage of change in peripheral resistance increases. The results indicate that chronic environmental exposure to low levels of arsenic alters the release of vasoactive substances, causes changes in oxidative stress, and increases blood pressure in female rats.
Assuntos
Acetilcolina/antagonistas & inibidores , Arsênio/toxicidade , Músculo Liso Vascular/efeitos dos fármacos , Estresse Oxidativo/fisiologia , Venenos/toxicidade , Acetilcolina/farmacologia , Animais , Arsênio/farmacocinética , Pressão Sanguínea/efeitos dos fármacos , Relação Dose-Resposta a Droga , Feminino , Glutationa/sangue , Cabelo/química , Hemodinâmica/efeitos dos fármacos , Técnicas In Vitro , Peroxidação de Lipídeos/efeitos dos fármacos , Relaxamento Muscular/efeitos dos fármacos , Óxido Nítrico/fisiologia , Nitroprussiato/farmacologia , Venenos/farmacocinética , Sintase do Porfobilinogênio/sangue , Ratos , Ratos Sprague-Dawley , Vasodilatadores/farmacologiaRESUMO
In this article, we will review some behavioral, pharmacological and neurochemical studies from our laboratory on mice, which might contribute to our understanding of the complex processes of memory consolidation and reconsolidation. We discuss the post-training (memory consolidation) and post-reactivation (memory reconsolidation) effects of icv infusions of hemicholinium, a central inhibitor of acetylcholine synthesis, of intraperitoneal administration of L-NAME, a non-specific inhibitor of nitric oxide synthase, of intrahippocampal injections of an inhibitor of the transcription factor NF-kappaB, and the exposure of mice to a new learning situation on retention performance of an inhibitory avoidance response. All treatments impair long-term memory consolidation and retrieval-induced memory processes different from extinction, probably in accordance with the 'reconsolidation hypothesis'.
Assuntos
Aprendizagem da Esquiva/efeitos dos fármacos , Hemicolínio 3/farmacologia , Memória/efeitos dos fármacos , NF-kappa B/farmacologia , NG-Nitroarginina Metil Éster/farmacologia , Acetilcolina/antagonistas & inibidores , Animais , Aprendizagem da Esquiva/fisiologia , Memória/fisiologia , Camundongos , Óxido Nítrico Sintase/antagonistas & inibidores , Ratos , Retenção Psicológica/efeitos dos fármacos , Retenção Psicológica/fisiologiaRESUMO
In this article, we will review some behavioral, pharmacological and neurochemical studies from our laboratory on mice, which might contribute to our understanding of the complex processes of memory consolidation and reconsolidation. We discuss the post-training (memory consolidation) and post-reactivation (memory reconsolidation) effects of icv infusions of hemicholinium, a central inhibitor of acetylcholine synthesis, of intraperitoneal administration of L-NAME, a non-specific inhibitor of nitric oxide synthase, of intrahippocampal injections of an inhibitor of the transcription factor NF-κB, and the exposure of mice to a new learning situation on retention performance of an inhibitory avoidance response. All treatments impair long-term memory consolidation and retrieval-induced memory processes different from extinction, probably in accordance with the "reconsolidation hypothesis".
Assuntos
Animais , Camundongos , Ratos , Aprendizagem da Esquiva/efeitos dos fármacos , /farmacologia , Memória/efeitos dos fármacos , NF-kappa B/farmacologia , NG-Nitroarginina Metil Éster/farmacologia , Acetilcolina/antagonistas & inibidores , Aprendizagem da Esquiva/fisiologia , Memória/fisiologia , Óxido Nítrico Sintase/antagonistas & inibidores , Retenção Psicológica/efeitos dos fármacos , Retenção Psicológica/fisiologiaRESUMO
Los inhibidores de 3-hidroxi-3 metil glutaril coenzima A reductasa (estatinas) son eficaces para el descenso de los nivelesde colesterol sérico y, consecuentemente, la prevención de la enfermedad isquémica cardíaca, cerebrovascular y vascularperiférica. Una de las principales limitaciones del uso de estas drogas es la aparición de sintomatología muscular como la elevación de la CK, mialgias, miositis o rabdomiolisis. La miastenia gravis (MG) es una enfermedad autoinmune caracterizada por la presencia de debilidad fluctuante de los músculos voluntarios. La enfermedad se desencadena por el ataque de anticuerpos dirigidos contra los receptores nicotínicosde acetilcolina (ACRA) localizados en la membrana del músculo a nivel de la unión neuromuscular. Existe un número interesante de fármacos que empeoran el curso de la enfermedad o que en algunos casos la "desenmascaran". Recientemente se publicaron casos de pacientes con MG que presentaron exacerbación de su enfermedad con laingesta de estatinas. Presentamos 11 pacientes que comenzaron con síntomas de MG luego de la toma de estas drogas. Seis recibieron atorvastatina (54.5%), tres simvastatina (27.3%) y dos rosuvastatina (18.2%).
3-hydroxi-3 metyl glutaryl coenzyme A reductase inhibitors, also known as statins, are effective in reducing plasmaticcholesterol and thus preventing cardiac, cerebral, and peripheral vascular ischemia. One of the main reasons that limit their use is the potential for muscular disorders, such as the increase of plasmatic CK, myalgia, myositis, and rhabdomyolysis. Myasthenia gravis (MG) is an autoimmune disease characterized by the presence of fluctuating voluntary muscle weakness. It is triggered by antibodies directed against nicotinic acetylcholine receptors (AChR) located at the neuromuscular junction, within the muscle membrane. A number of drugs may either unmask the disease or worsen it when installed. Recent publications have reported on cases of MG who aggravated their condition with the intake of statins. Here, we report on eleven patients who presented symptoms of MG after medication with statins. Six patients received atorvastatin (54.5%), three simvastatin (27.3%), and two rosuvastatin (18.2%).
Assuntos
Masculino , Feminino , Acetilcolina/antagonistas & inibidores , Inibidores de Hidroximetilglutaril-CoA Redutases/efeitos adversos , Inibidores da Colinesterase/uso terapêutico , Miastenia Gravis/etiologia , Miastenia Gravis/induzido quimicamente , Recidiva , Doenças NeuromuscularesRESUMO
CF-1 male mice were trained in an inhibitory avoidance task using a high footshock (1,2 mA, 50 Hz, 1 sec) in order to reduce the influence of extinction on retention performance. At 2, 7, 14, or 30 d after training, the first retention test was performed and hemicholinium (HC-3, 1.0 microg/mice), a specific inhibitor of high-affinity choline uptake in brain cholinergic neurons, was given intracerebroventricularly immediately after. Twenty four hours after treatment, mice were tested in an inhibitory avoidance task during five consecutive days, each 24 h apart. Retention performance was impaired by HC-3 when the first re-exposure took place at 2, 7, or 14 d, but the effect was no longer seen when re-exposure occurred 30 d after training. We did not find spontaneous recovery 21 d after training, when memory was retrieved 2 d after training and HC-3 was given immediately after. Although we cannot definitively discard a retrieval deficit, this lack of spontaneous recovery is in accordance with the storage-deficit interpretation. These results confirm and extend previous ones, suggesting that central cholinergic mechanisms are involved in the hypothetical reconsolidation memory processes of an inhibitory avoidance task in mice and also suggest that this participation depends on the "age" of the original memory trace. This implies that the vulnerability of a reactivated memory to a specific treatment, as the one used in this study, inversely correlates with the age of the original memory, and it is likely to determine memory reconsolidation processes.
Assuntos
Acetilcolina/fisiologia , Colinérgicos/administração & dosagem , Hemicolínio 3/administração & dosagem , Rememoração Mental/efeitos dos fármacos , Inibidores da Captação de Neurotransmissores/administração & dosagem , Acetilcolina/antagonistas & inibidores , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/fisiologia , Injeções Intraventriculares , Masculino , Rememoração Mental/fisiologia , Camundongos , Fatores de TempoRESUMO
Himatanthus lancifolius, popularly known as "agoniada" in Brazil, is largely used in folk medicine against asthma, dysmenorrhea and as an emenagogue and abortive. This study reveals the effects of an alkaloid rich fraction (AlkF) obtained from the bark of Himatanthus lancifolius in vascular and non-vascular smooth muscle responsiveness. Incubation of AlkF (3-30 microg/ml) during 15 min generates a concentration-related and fully reversible reduction in maximal contractile responses evoked by acetylcholine and phenylephrine in rat jejune and aorta preparations, respectively. Exposition of endothelium-denuded pre-contracted rat aorta rings to AlkF results in a complete relaxation, with EC(50) of 22.2 (16.2-28.2 microg/ml). AlkF is also able to induce a concentration-related rightward shift of cumulative concentration curves for calcium in uterus and aorta rings maintained in depolarizing nutritive solution. Moreover, addition of AlkF in calcium-free solution also reduces, in a concentration-dependent manner, the ability of caffeine and phenylephrine to contract aorta rings. This study reveals that the bark of Himatanthus lancifolius possesses one or more indole alkaloids able to alter non-vascular and vascular smooth muscle responsiveness, an event that may involve the blocking of calcium entry or changes on intracellular calcium utilization or mobilization.
Assuntos
Alcaloides/farmacologia , Apocynaceae/química , Músculo Liso/efeitos dos fármacos , Acetilcolina/antagonistas & inibidores , Acetilcolina/farmacologia , Alcaloides/química , Animais , Aorta Torácica/efeitos dos fármacos , Cálcio/fisiologia , Cloreto de Cálcio/farmacologia , Cromatografia Líquida de Alta Pressão , Feminino , Íleo/efeitos dos fármacos , Técnicas In Vitro , Masculino , Contração Muscular/efeitos dos fármacos , Tono Muscular/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Fenilefrina/farmacologia , Casca de Planta/química , Ratos , Ratos Wistar , Contração Uterina/efeitos dos fármacos , Ducto Deferente/efeitos dos fármacos , Vasoconstritores/farmacologia , Vasodilatadores/antagonistas & inibidores , Vasodilatadores/farmacologiaRESUMO
1. Pregnancy in rats is characterized by a reduction in arterial pressure that is associated with a decreased response to vasoconstrictors. However, the responses to vasodilators in isolated vessels remain controversial and are not well established in hypertensive pregnant rats. 2. In the present study, we investigated the effect of pregnancy on the bradykinin (BK)-induced vasodilator responses of the isolated mesenteric arterial bed (MAB) from Wistar normotensive and spontaneously hypertensive rats (SHR) and determined the role of nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and angiotensin-converting enzyme (ACE) in these responses. 3. Mean arterial pressure (MAP) in pregnant normotensive and pregnant hypertensive rats (93 +/- 1 and 122 +/- 2 mmHg, respectively) was lower than in non-pregnant controls (128 +/- 1 and 163 +/- 2 mmHg, respectively; P < 0.05). In MAB isolated from normotensive rats and precontracted with phenylephrine, the effects of bradykinin, acetylcholine (ACh) and nitroglycerine (NG) were not influenced by pregnancy. In contrast, the vasodilator responses to BK were significantly reduced in pregnant compared with non-pregnant SHR and seemed to be specific to BK. 4. The ACE inhibitor captopril potentiated BK vasodilator responses and abolished the differences between pregnant and non-pregnant SHR. Inhibition of nitric oxide (NO) synthase by N(G)-nitro-L-arginine methyl ester (l-NAME) significantly reduced the vasodilator effect of BK in all groups. In the presence of l-NAME plus high K+ solution (47 mmol/L), BK-induced vasodilation was completely blocked. The NO-dependent component of the responses seems to be more important in hypertensive rats and pregnancy does not modify this profile. 5. Our results suggest that increased ACE activity may be involved in the pregnancy associated reduction in vasodilator responses to BK in the MAB of hypertensive rats. Pregnancy does not modify the relative contribution of the EDHF and NO to the vasodilator effect of BK.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Bradicinina/antagonistas & inibidores , Bradicinina/farmacologia , Captopril/farmacologia , Hipertensão/fisiopatologia , Complicações Cardiovasculares na Gravidez/fisiopatologia , Vasodilatação/efeitos dos fármacos , Acetilcolina/antagonistas & inibidores , Acetilcolina/farmacologia , Animais , Fatores Biológicos/metabolismo , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/farmacologia , Feminino , Técnicas In Vitro , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico/fisiologia , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase Tipo III , Peptidil Dipeptidase A/metabolismo , Gravidez , Ratos , Ratos Endogâmicos SHR , Ratos Wistar , Circulação Esplâncnica/efeitos dos fármacos , Vasodilatadores/antagonistas & inibidores , Vasodilatadores/farmacologiaRESUMO
The mechanisms involved in the cardioprotector effect of red wine have not yet been completely elucidated but probably an endothelium-dependent vasodilator action may play a significant role in this effect. Experiments were undertaken to determine whether a Brazilian red wine (BRW) induces vasodilation in the mesenteric vascular bed (MVB) and an antihypertensive effect was also assessed in rats with NO-deficient hypertension. In MVB precontracted with norepinephrine, BRW (alcohol-free lyophilized) induces a long-lasting endothelium-dependent vasodilation that is not reduced by indomethacin. Inhibition of NO-synthase by NG-nitro-L-arginine methyl ester (L-NAME) and guanylyl cyclase by 1H-[1,2,3] oxadiazolo [4,4-a]quinoxalin-1-one (ODQ) reduces the vasodilator effect of BRW. In vessels precontracted with norepinephrine and depolarized with KCl (25 Mm) or treated with Ca-dependent K channel blockers charybdotoxin (ChTx) plus apamin, the effect of BRW was significantly reduced. However, this effect is not affected by ATP-dependent K (KATP) channel blocker (glibenclamide). The residual vasodilator effect of BRW observed in vessels pretreated with ChTx plus apamin is completely abolished by ChTx plus apamin plus L-NAME. Concentrations of atropine, pyrilamine, yohimbine, and HOE 140 that significantly reduced the vasodilator effect of acetylcholine, histamine, clonidine, and bradykinin, respectively did not change the vasodilator effect of BRW. Chronic oral administration of BRW induced a significant reduction in systolic, mean and diastolic arterial pressure in rats with L-NAME hypertension. The present results demonstrated that vasodilator effect of BRW is dependent on endothelium-derived hyperpolarizing factor (EDHF) in combination with nitric oxide (NO). The antihypertensive effect of red wine demonstrated in the present study may play a significant role on the cardioprotective action of chronic red wine consumption.
Assuntos
Consumo de Bebidas Alcoólicas/efeitos adversos , Bradicinina/análogos & derivados , Endotélio Vascular/fisiologia , Hipertensão/prevenção & controle , Vasodilatação/fisiologia , Acetilcolina/antagonistas & inibidores , Acetilcolina/farmacologia , Administração Oral , Animais , Apamina/farmacologia , Atropina/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Bradicinina/farmacologia , Brasil , Charibdotoxina/farmacologia , Clonidina/antagonistas & inibidores , Clonidina/farmacologia , Ácido Desoxicólico/farmacologia , Quimioterapia Combinada , Flavonoides/análise , Flavonoides/antagonistas & inibidores , Flavonoides/farmacologia , Glibureto/farmacologia , Guanilato Ciclase/antagonistas & inibidores , Hipertensão/induzido quimicamente , Indometacina/farmacologia , Masculino , Artérias Mesentéricas/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , NG-Nitroarginina Metil Éster/efeitos adversos , Óxido Nítrico Sintase/antagonistas & inibidores , Nitroglicerina/farmacologia , Norepinefrina/farmacologia , Oxidiazóis/química , Oxidiazóis/farmacologia , Perfusão , Fenóis/análise , Fenóis/antagonistas & inibidores , Fenóis/farmacologia , Polifenóis , Cloreto de Potássio/farmacologia , Pressão , Pirilamina/farmacologia , Quinazolinas/química , Quinazolinas/farmacologia , Quinoxalinas/farmacologia , Ratos , Ratos Wistar , Vasoconstrição/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Vinho/efeitos adversos , Ioimbina/farmacologiaRESUMO
The venoms of some Bothrops species produce neuromuscular blockade in avian and mammalian nerve-muscle preparations in vitro. In this study, we compared the neuromuscular activities (myotoxicity and neurotoxicity) of venoms from several Brazilian species of Bothrops (B. jararaca, B. jararacussu, B. moojeni, B. erythromelas and B. neuwiedi) in chick isolated biventer cervicis muscle preparations and examined their neutralization by commercial antivenom. All of the venoms (50-200 microg/ml, n = 3 - 7 each) induced long-lasting, concentration-dependent muscle contracture and twitch-tension blockade, and also inhibited the muscle responses to acetylcholine and KCl. Preincubation of the venoms (200 microg/ml) with bothropic antivenom (0.2 ml) for 30 min at 37 degrees C prevented the twitch-tension blockade to different extents, with the protection varying from 0.5% (B. neuwiedi) to 88% (B. moojeni). Complete protection against the neuromuscular action of B. neuwiedi venom was observed only with a mixture of bothropic and crotalic antivenoms. The venoms caused either high (B. jararacussu, B. neuwiedi and B. moojeni) or low (B. jararaca and B. erythromelas) creatine kinase release. Morphologically, myonecrosis was greatest with B. jararacussu venom (98-100% of fibers damaged) and least with B. jararaca venom (74% damage). The extent of neutralization by bothropic antivenom was B. jararaca (93%)>B. erythromelas (65.8%)>B. moojeni (30.7%)>B. neuwiedi (20%)>B. jararacussu (no neutralization). Despite this variation in neutralization, enzyme-linked immunosorbent assays indicated similar immunoreactivities for the venoms, although immunoblots revealed quantitative variations in the bands detected. These results show that Bothrops venoms produce varying degrees of neuromuscular blockade in chick nerve-muscle preparations. The variable protection by antivenom against neuromuscular activity indicates that the components responsible for the neuromuscular action may differ among the venoms.
Assuntos
Antivenenos/farmacologia , Bothrops , Venenos de Crotalídeos/toxicidade , Contração Muscular/efeitos dos fármacos , Junção Neuromuscular/efeitos dos fármacos , Acetilcolina/antagonistas & inibidores , Animais , Brasil , Galinhas , Creatina Quinase/metabolismo , Venenos de Crotalídeos/antagonistas & inibidores , Eletroforese em Gel de Poliacrilamida , Ensaio de Imunoadsorção Enzimática , Immunoblotting , Dose Letal Mediana , Masculino , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/patologia , Necrose , Cloreto de Potássio/antagonistas & inibidoresRESUMO
1. At the mouse neuromuscular junction, adenosine (AD) and the A(1) agonist 2-chloro-N(6)-cyclopentyl-adenosine (CCPA) induce presynaptic inhibition of spontaneous acetylcholine (ACh) release by activation of A(1) AD receptors through a mechanism that is still unknown. To evaluate whether the inhibition is mediated by modulation of the voltage-dependent calcium channels (VDCCs) associated with tonic secretion (L- and N-type VDCCs), we measured the miniature end-plate potential (mepp) frequency in mouse diaphragm muscles. 2. Blockade of VDCCs by Cd(2+) prevented the effect of the CCPA. Nitrendipine (an L-type VDCC antagonist) but not omega-conotoxin GVIA (an N-type VDCC antagonist) blocked the action of CCPA, suggesting that the decrease in spontaneous mepp frequency by CCPA is associated with an action on L-type VDCCs only. 3. As A(1) receptors are coupled to a G(i/o) protein, we investigated whether the inhibition of PKA or the activation of PKC is involved in the presynaptic inhibition mechanism. Neither N-(2[p-bromocinnamylamino]-ethyl)-5-isoquinolinesulfonamide (H-89, a PKA inhibitor), nor 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine (H-7, a PKC antagonist), nor phorbol 12-myristate 13-acetate (PHA, a PKC activator) modified CCPA-induced presynaptic inhibition, suggesting that these second messenger pathways are not involved. 4. The effect of CCPA was eliminated by the calmodulin antagonist N-(6-aminohexil)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7) and by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-acetoxymethyl ester epsilon6TDelta-BM, which suggests that the action of CCPA to modulate L-type VDCCs may involve Ca(2+)-calmodulin. 5. To investigate the action of CCPA on diverse degrees of nerve terminal depolarization, we studied its effect at different external K(+) concentrations. The effect of CCPA on ACh secretion evoked by 10 mm K(+) was prevented by the P/Q-type VDCC antagonist omega-agatoxin IVA. 6. CCPA failed to inhibit the increases in mepp frequency evoked by 15 and 20 mm K(+). We demonstrated that, at high K(+) concentrations, endogenous AD occupies A1 receptors, impairing the action of CCPA, since incubation with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, an A(1) receptor antagonist) and adenosine deaminase (ADA), which degrades AD into the inactive metabolite inosine, increased mepp frequency compared with that obtained in 15 and 20 mm K(+) in the absence of the drugs. Moreover, CCPA was able to induce presynaptic inhibition in the presence of ADA. It is concluded that, at high K(+) concentrations, the activation of A(1) receptors by endogenous AD prevents excessive neurotransmitter release.
Assuntos
Acetilcolina/metabolismo , Adenosina/farmacologia , Junção Neuromuscular/metabolismo , Terminações Pré-Sinápticas/metabolismo , Acetilcolina/antagonistas & inibidores , Agonistas do Receptor A1 de Adenosina , Animais , Relação Dose-Resposta a Droga , Masculino , Camundongos , Junção Neuromuscular/efeitos dos fármacos , Terminações Pré-Sinápticas/efeitos dos fármacos , Receptor A1 de Adenosina/metabolismoRESUMO
The action of the tricyclic antidepressant clomipramine on membrane currents elicited by acetylcholine was studied in Xenopus oocytes expressing neuronal alpha2beta4 nicotinic acetylcholine receptors. Clomipramine inhibited the acetylcholine responses rapidly and reversibly, with a similar IC(50) when the oocytes were preincubated with clomipramine (1.3+/-0.2 microM) or when they were exposed simultaneously with acetylcholine and clomipramine (1.5+/-0.3 microM). The EC(50) was 39.9+/-2.1 microM for acetylcholine alone and 65.7+/-3.6 microM for acetylcholine in the presence of 2 microM clomipramine. The inhibitory effect of clomipramine was weakly voltage-dependent, with an electric distance of approximately 0.14. Moreover, clomipramine increased the rate of decay of currents elicited by acetylcholine. From all of these, we conclude that clomipramine reversibly and noncompetitively regulates neuronal alpha2beta4 nicotinic acetylcholine receptors by blocking the open receptor-channel complex at a site close to the extracellular vestibule of the channel. The actions of clomipramine on neuronal nicotinic acetylcholine receptors may play an important role in the treatment of mental depression and other mood disorders.
Assuntos
Antidepressivos Tricíclicos/farmacologia , Clomipramina/farmacologia , Receptores Nicotínicos/efeitos dos fármacos , Acetilcolina/antagonistas & inibidores , Animais , Relação Dose-Resposta a Droga , Oócitos/efeitos dos fármacos , XenopusRESUMO
Phoneutria nigriventer spider venom has been described as acting on several cardiovascular sites. In the present paper, a semi-purified fraction of this spider venom was studied to observe any contractile or relaxing effect in rat mesenteric arterial rings (MAR). Spider venom was first fractionated by gel filtration and subsequently by gradual isocratic steps in 0.1% trifluoroacetic acid. The first fraction of this last fractionation step is studied in the present paper and due to its main effect, it was named NORF (nitric oxide releasing fraction). No direct contractile effect was induced by NORF in relaxed MAR, suggesting no NORF-induced neurotransmitter release in this preparation. No significant influence of NORF was observed on concentration-response curves to phenylephrine on endothelium-denuded MAR, but a significant inhibitory shift of concentration-respense curves was observed on endothelium-preserved MAR (EC50 = 0.39 +/- 0.07 microM for control and EC50 = 0.68 +/- 0.14 microM with NORF). NORF induced concentration-dependent relaxation in endothelium-preserved phenylephrine pre-contracted MAR but not in endothelium-denuded MAR. NORF-induced relaxation was inhibited by the nitric oxide synthase inhibitor L-NAME (N(omega)-nitro-arginine methyl ester). Indomethacin or HOE-140 (D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin) had no significant effect on NORF-induced relaxation. Acetylcholine- and NORF-induced relaxation of pre-contracted MAR were differently inhibited by atropine. The pA2 value for atropine-acetylcholine was 9.78 +/- 0.06 and that for atropine-NORF was 8.53 +/- 0.30 (P<0.01). These observations suggest that NORF induces concentration-dependent liberation of nitric oxide from MAR endothelium and that a non-muscarinic mechanism might be involved in this effect. Our data suggest no involvement of prostanoids or bradykinin in the relaxing mechanism.
Assuntos
Endotélio Vascular/fisiologia , Artérias Mesentéricas/efeitos dos fármacos , Venenos de Aranha/farmacologia , Vasodilatação/efeitos dos fármacos , Acetilcolina/antagonistas & inibidores , Acetilcolina/farmacologia , Animais , Atropina/farmacologia , Bradicinina/farmacologia , Interações Medicamentosas , Feminino , Técnicas In Vitro , Masculino , Artérias Mesentéricas/fisiologia , Óxido Nítrico/antagonistas & inibidores , Óxido Nítrico/biossíntese , Doadores de Óxido Nítrico/antagonistas & inibidores , Doadores de Óxido Nítrico/farmacologia , Fenilefrina/farmacologia , Ratos , AranhasRESUMO
Os efeitos produzidos pelas peçonhas escorpiônicas säo consequentes, em sua maioria, à liberaçäo de acetilcolina (ACh) e catecolaminas. A verificaçäo de que o magnésio (Mg2+) inibe a liberaçäo de ACh em razäo de bloquear o influxo de cálcio nas terminaçöes nervosas, levou-nos a investigar a açäo deste cátion sobre os distúrbios produzidos pelas peçonhas escorpiônicas. Relatamos na presente comunicaçäo a açäo do Mg2+ sobre os efeitos induzidos pelas peçonhas dos escorpiöes Tityus serrulatus, T. bahiensis e Centruroides sculpturatus nas preparaçöes isoladas nervo frênico-diafragma, íleo, canal deferente e átrios de rato e in vivo, em ratos anestesiados com registro da pressäo arterial e do eletrocardiograma. Os efeitos da peçonha dos escorpiöes nas preparaçöes isoladas foram abolidos ou muito atenuados pelo Mg2+. O Mg2+, no entanto, somente antagonizou os efeitos da peçonha de C. sculpturatus no íleo de rato. Em ratos anestesiados, a hipertensäo e arritmias provocadas pela peçonha de T. serrulatus foram revertidas com exclusäo de bradicardia pela injeçäo do Mg2+. A peçonha de C. sculpturatus na maioria das experiências causou hipotensäo e arritmias de pequena gravidade. O Mg2+ reverteu as arritmias, mas causou quedas acentuadas da pressäo arterial. Os resultados da pesquisa sugerem o emprego do Mg2+ em acidentes graves na ausência de hipotensäo e bradicardia, produzidos por T. serrulatus e T. bahiensis. Parece contra-indicado nos acidentes causados por C. sculpturatus em vista de seu efeito acima referido na pressäo arterial.
Assuntos
Animais , Ratos , Acetilcolina/antagonistas & inibidores , Catecolaminas/antagonistas & inibidores , Átrios do Coração/efeitos dos fármacos , Íleo , Magnésio/farmacologia , Magnésio/uso terapêutico , Nervo Frênico , Picada de Aranha/terapia , Ducto Deferente/efeitos dos fármacos , Venenos de Escorpião/antagonistas & inibidores , Venenos de Escorpião/farmacologia , Arritmias Cardíacas/terapia , Frequência Cardíaca , Pressão Arterial , Ratos Wistar , EscorpiõesRESUMO
4-Aminobenzovesamicol was used to test whether activation of protein kinase C protects the vesicular acetylcholine transporter from interaction with vesamicol-like drugs. The essentially irreversible vesamicol analog inhibits the release of newly synthesized [3H]acetylcholine from stimulated hippocampal slices. Prior activation of protein kinase C with a phorbol ester prevented the inhibition of [3H]acetylcholine release, but activation of protein kinase C after the exposure to the irreversible analog did not prevent the effect of the drug. Binding of 4-aminobenzovesamicol in hippocampal synaptosomes, assayed using [3H]vesamicol and back-titration, was decreased by activation of protein kinase C prior to analog exposure but not by activation subsequent to exposure. We propose that phosphorylation of the vesicular acetylcholine transporter prevents the binding of vesamicol-like drugs.
Assuntos
Proteínas de Transporte/metabolismo , Proteínas de Membrana Transportadoras , Piperidinas/metabolismo , Proteínas de Transporte Vesicular , Acetilcolina/antagonistas & inibidores , Acetilcolina/biossíntese , Animais , Estimulação Elétrica , Ativação Enzimática/fisiologia , Feminino , Hipocampo/metabolismo , Técnicas In Vitro , Masculino , Piperidinas/farmacologia , Proteína Quinase C/metabolismo , Ratos , Ratos Wistar , Proteínas Vesiculares de Transporte de AcetilcolinaRESUMO
The methanolic extract of the aerial portion of Chenopodium chilense Schrad., used in Chilean traditional medicine as a remedy for stomach-ache, has been found to exert the major spasmolytic activity in acetylcholine contracted rat ileum. This extract, with a complex flavonoid patterns on thin layer chromatography (TLC) analysis, is practically non-toxic both for rats and brine shrimp Artemia salina in acute toxicity test.
Assuntos
Chenopodiaceae/química , Íleo/efeitos dos fármacos , Parassimpatolíticos/farmacologia , Plantas Medicinais/química , Acetilcolina/antagonistas & inibidores , Animais , Decápodes , Íleo/fisiologia , Técnicas In Vitro , Contração Muscular/efeitos dos fármacos , RatosRESUMO
AIM: To examine the effects and affinity of some phenothizines (trifluoperazine, Tri and chlorpromazine, Chl) and antidepressant (imipramine, Imi) drugs on acetylcholine (ACh)-induced uterine contraction. METHODS: Isotonic contractions of rat uterine strips were recorded. ACh was administrated to induce maximal contraction before exchange of nutrient solution. ACh was added 5 min after the testing drugs. The nutrient solution was exchanged 4 times after each agonist (ACh or other agents) to produce maximal contraction. RESULTS: Atropine (Atr, 0.029-2.9 mumol.L-1), 4-DAMP (3.6-360 nmol.L-1), pirenzepine (Pir, 0.23-23.5 mumol.L-1), and AF-DX 116 (0.7-35.6 mumol.L-1) competitively antagonized the muscular uterine concentration induced by ACh (0.068-36068 mumol.L-1). The Schild plot was linear (r = 1.00). The pKB and slopes values (95% confidence limits) were 9.28 +/- 0.12 and 1.00 +/- 0.10 to Atr, 9.06 +/- 0.10 and 1.10 +/- 0.08 to 4-DAMP, 7.03 +/- 0.15 and 0.99 +/- 0.12 to Pir, and 5.60 +/- 0.08 and 1.00 +/- 0.19 to AF-DX 116. Tri 0.01-2 mumol.L-1 (pKB = 8.39 +/- 0.04) and Imi 94-940 nmol.L-1 (pKB = 7.21 +/- 0.10) produced also a competitive antagonism of the muscular uterine contraction induced by ACh (r = 1.00), but the slope was only 0.60 +/- 0.03 to Tri or 0.83 +/- 0.16 to Imi. Chl 2.8-5.6 mumol.L-1 produced a weak antagonism on amplitude of muscular contraction induced by the cholinomimetic. CONCLUSION: The muscarinic receptors on uterus behaved as M3 subtype. Tri and Imi, but not Chl, were competitive antagonist of muscarinic receptors of uterus. Imi behaved a simple competitive antagonist at a single site on myometrium, but Tri was not a simple competitive agent at a single site.
Assuntos
Acetilcolina/antagonistas & inibidores , Antidepressivos Tricíclicos/farmacologia , Antipsicóticos/farmacologia , Clorpromazina/farmacologia , Imipramina/farmacologia , Trifluoperazina/farmacologia , Contração Uterina/efeitos dos fármacos , Animais , Feminino , Técnicas In Vitro , Ratos , Ratos WistarAssuntos
Humanos , Criança , Interações Medicamentosas , Bloqueadores Neuromusculares/uso terapêutico , Pancurônio/farmacologia , Junção Neuromuscular/fisiologia , Brometo de Vecurônio/farmacologia , Acetilcolina/agonistas , Acetilcolina/antagonistas & inibidores , Acetilcolina/farmacologia , Interações Medicamentosas , Bloqueadores Neuromusculares/classificação , Bloqueadores Neuromusculares/farmacologia , Pancurônio , Pancurônio/efeitos adversos , Unidades de Terapia Intensiva Pediátrica/normas , Junção Neuromuscular/anatomia & histologia , Brometo de Vecurônio , Brometo de Vecurônio/efeitos adversosAssuntos
Humanos , Criança , Bloqueadores Neuromusculares/uso terapêutico , Junção Neuromuscular/fisiologia , Brometo de Vecurônio/farmacologia , Pancurônio/farmacologia , Interações Medicamentosas , Bloqueadores Neuromusculares/classificação , Bloqueadores Neuromusculares/farmacologia , Junção Neuromuscular/anatomia & histologia , Brometo de Vecurônio/administração & dosagem , Brometo de Vecurônio/efeitos adversos , Pancurônio/administração & dosagem , Pancurônio/efeitos adversos , Unidades de Terapia Intensiva Pediátrica/normas , Interações Medicamentosas , Acetilcolina/agonistas , Acetilcolina/antagonistas & inibidores , Acetilcolina/farmacologiaRESUMO
1. The canine isolated spleen was perfused at constant flow with warmed (37 degrees C) Krebs solution while the splenic arterial perfusion pressure (SAPP) and spleen weight were recorded continuously. An augmented smooth muscle tone was maintained by a continuous intra-arterial infusion of noradrenaline (0.01-0.1 mumol min-1) throughout the experiment. 2. Intra-arterial infusion of indomethacin (5.6 microM) significantly elevated (P < 0.05) the augmented vascular tone and the subsequent infusion of L-NAME (10 microM) further raised this vascular tone significantly (P < 0.01). 3. The splenic vasoconstrictor response to L-NAME was significantly (P < 0.05) reduced by the subsequent infusion of L-arginine (300 microM) but not of D-arginine (300 microM). 4. Neither L-NAME nor D-NAME had any effect on the basal vascular tone or the spleen weight in conditions of either basal or augmented tone. 5. Bolus injection of acetylcholine, substance P, sodium nitroprusside and isoprenaline caused short-lasting reductions in the SAPP. 6. The splenic vasodilator responses to ACh and SP, but not those to SNP and ISO, were significantly (P < 0.05) reduced by the infusion of L-NAME (10 microM), methylene blue (30 microM) but not of D-NAME (10 microM). 7. The reductions in the vasodilator responses to ACh and SP caused by L-NAME were partially reversed by L-arginine (300 microM), but not by D-arginine (300 microM). 8. The results demonstrate the contribution of nitric oxide (NO) release to the maintenance of the augmented splenic vascular tone and also the contribution of NO to the splenic vasodilator responses to ACh and SP.