RESUMO
Previous studies from our laboratory have shown sex differences in the behavioral, molecular, and neurochemical manifestations of morphine withdrawal and they were related to an increased sensitivity to morphine effects in males. In addition, we observed an interaction between the GABAergic and opioid systems that could also be sex-dependent. Baclofen, a GABAB receptor agonist, prevented the somatic expression and the molecular and neurochemical changes induced by morphine withdrawal syndrome in mice. On the contrary, little is known about baclofen effects in the rewarding properties of morphine in male and female mice. The present study aimed to explore the effect of baclofen (1, 2 and 3 mg/kg, i.p.) pretreatment in the rewarding effects induced by morphine (7 mg/kg, s.c.) and its effect on c-Fos and brain-derived neurotrophic factor (BDNF) expression induced by the rewarding properties of morphine in prepubertal male and female mice. Baclofen (2 mg/kg) pretreatment prevented the rewarding effects of morphine only in male mice, while baclofen (3 mg/kg) reduced these effects in both sexes. Moreover, the rewarding effects of morphine were associated with a decrease of BDNF and c-Fos expression cingulate cortex, nucleus accumbens shell, cornu ammonis 1 (CA1), and cornu ammonis 3 (CA3) areas of the hippocampus only in male mice. In addition, baclofen pretreatment prevented these changes in BDNF, but not in c-Fos expression. In conclusion, our results show that GABAB receptors have a regulatory role in the rewarding effects of morphine that could be of interest for a potential future therapeutic application in opioid use disorders.
Assuntos
Baclofeno , Fator Neurotrófico Derivado do Encéfalo , Morfina , Proteínas Proto-Oncogênicas c-fos , Recompensa , Animais , Baclofeno/farmacologia , Masculino , Feminino , Morfina/farmacologia , Camundongos , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Agonistas dos Receptores de GABA-B/farmacologia , Caracteres Sexuais , Comportamento Animal/efeitos dos fármacos , Fatores SexuaisRESUMO
Previous studies in our laboratory showed an interaction between the GABAergic and opioid systems involved in the analgesic effect of baclofen (BAC). Furthermore, it is known that sex differences exist regarding various pharmacological responses of morphine (MOR) and they are related to an increased sensitivity to MOR effects in males. The aims of the present study were to evaluate the possible involvement of the GABAB receptors in the antinociceptive responses induced by MOR (1, 3 and 9â¯mg/kg, s.c.) administration using both pharmacological (BAC 2â¯mg/kg, i.p.; and 2-OH-saclofen, SAC 0.3â¯mg/kg, intra cisterna magna) and genetic approaches (GABAB1 knockout mice; GABAB1 KO) in mice of both sexes. In addition, we explored the alterations in c-Fos expression of different brain areas involved in the antinociceptive effect of MOR using both approaches. The pharmacological approach showed a higher dose-dependent antinociceptive effect of MOR in male mice compared to female mice. BAC and SAC pretreatment potentiated and attenuated the antinociceptive effect of MOR, respectively, in both sexes. The genetic approach revealed a dose-dependent antinociceptive effect of MOR in the wild type mice, but not in the GABAB1 KO mice and no sex differences were observed. Additionally, BAC and SAC pretreatment and the lack of GABAB1 subunit of the GABAB receptor prevented the changes observed in c-Fos expression in the cingulate cortex and nucleus accumbens of male mice. Our results suggest that the GABAB receptors are involved in the MOR antinociceptive effect of both male and female mice.
Assuntos
Analgésicos/farmacologia , Morfina/farmacologia , Receptores de GABA-B/genética , Receptores de GABA-B/metabolismo , Analgésicos/administração & dosagem , Animais , Baclofeno/administração & dosagem , Baclofeno/análogos & derivados , Baclofeno/farmacologia , Comportamento Animal/efeitos dos fármacos , Relação Dose-Resposta a Droga , Feminino , Agonistas dos Receptores de GABA-B/administração & dosagem , Agonistas dos Receptores de GABA-B/farmacologia , Técnicas de Inativação de Genes , Genes fos/genética , Genótipo , Giro do Cíngulo/efeitos dos fármacos , Giro do Cíngulo/metabolismo , Locomoção/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Morfina/administração & dosagem , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Proteínas Proto-Oncogênicas c-fos/imunologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Fatores Sexuais , Transdução de Sinais/efeitos dos fármacosRESUMO
It has been demonstrated that GABAB receptors modulate nicotine (NIC) reward effect; nevertheless, the mechanism implicated is not well known. In this regard, we evaluated the involvement of GABAB receptors on the behavioral, neurochemical, biochemical and molecular alterations associated with the rewarding effects induced by NIC in mice, from a pharmacological and genetic approach. NIC-induced rewarding properties (0.5 mg/kg, subcutaneously, sc) were evaluated by conditioned place preference (CPP) paradigm. CPP has three phases: preconditioning, conditioning and postconditioning. GABAB receptor antagonist 2-hydroxysaclofen (0.25, 0.5 and 1 mg/kg; intraperitoneally, ip) or the GABAB receptor agonist baclofen (3 mg/kg; ip) was injected before NIC during the conditioning phase. GABAB1 knockout (GABAB1 KO) mice received NIC during the conditioning phase. Vehicle and wild-type controls were employed. Neurochemical (dopamine, serotonin and their metabolites), biochemical (nicotinic receptor α4ß2, α4ß2nAChRs) and molecular (c-Fos) alterations induced by NIC were analyzed after the postconditioning phase by high-performance liquid chromatography (HPLC), receptor-ligand binding assays and immunohistochemistry, respectively, in nucleus accumbens (Acb), prefrontal cortex (PFC) and ventral tegmental area (VTA). NIC induced rewarding effects in the CPP paradigm and increased dopamine levels in Acb and PFC, α4ß2nAChRs density in VTA and c-Fos expression in Acb shell (AcbSh), VTA and PFC. We showed that behavioral, neurochemical, biochemical and molecular alterations induced by NIC were prevented by baclofen. However, in 2-hydroxysaclofen pretreated and GABAB1 KO mice, these alterations were potentiated, suggesting that GABAB receptor activity is necessary to control alterations induced by NIC-induced rewarding effects. Therefore, the present findings provided important contributions to the mechanisms implicated in NIC-induced rewarding effects.
Assuntos
Encéfalo/efeitos dos fármacos , Condicionamento Psicológico/efeitos dos fármacos , Nicotina/farmacologia , Agonistas Nicotínicos/farmacologia , Receptores de GABA-B/efeitos dos fármacos , Animais , Baclofeno/análogos & derivados , Baclofeno/farmacologia , Encéfalo/metabolismo , Dopamina/metabolismo , Agonistas dos Receptores de GABA-B/farmacologia , Antagonistas de Receptores de GABA-B/farmacologia , Masculino , Camundongos , Camundongos Knockout , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Proteínas Proto-Oncogênicas c-fos/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-fos/metabolismo , Receptores de GABA-B/genética , Receptores Nicotínicos/efeitos dos fármacos , Receptores Nicotínicos/metabolismo , Recompensa , Serotonina/metabolismo , Área Tegmentar Ventral/efeitos dos fármacos , Área Tegmentar Ventral/metabolismoRESUMO
In previous studies we have shown that baclofen, a selective GABAB receptor agonist, prevents the somatic expression and reestablishes the dopamine and µ-opioid receptors levels, modified during naloxone-precipitated morphine withdrawal syndrome in male and female mice. There are no previous reports regarding sex differences in the elevated plus maze (EPM) and the expression of BDNF in morphine-withdrawn mice. The present study analyses the behavioral and biochemical variations during morphine withdrawal in mice of both sexes, and whether these variations are prevented with baclofen. Swiss-Webster albino prepubertal mice received morphine (2 mg/kg, i.p.) twice daily, for 9 consecutive days. On the 10th day, one group of morphine-treated mice received naloxone (opioid receptor antagonist; 6 mg/kg, i.p.) 1 h after the last dose of morphine to precipitate withdrawal. A second group received baclofen (2 mg/kg, i.p.) before naloxone administration. The EPM behavior was measured during 15 min after naloxone injection. The expression of BDNF-positive cells was determined by immunohistochemistry. Withdrawn male mice showed a higher percentage of time spent and number of entries to the open arms compared to withdrawn female mice. Baclofen prevented this behavior in both sexes. BDNF expression decreased in the AcbC, BNST, CeC, and CA3 of the hippocampus while increased in the BLA of morphine withdrawn male. Baclofen pretreatment prevented the BDNF expression observed in morphine withdrawn male mice in all the brain areas studied except in the CeC. Baclofen prevention of the EPM behavior associated to morphine withdrawal could be partially related to changes in BDNF expression.
Assuntos
Baclofeno/farmacologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Agonistas dos Receptores de GABA-B/farmacologia , Aprendizagem em Labirinto , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Animais , Baclofeno/administração & dosagem , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Fator Neurotrófico Derivado do Encéfalo/genética , Feminino , Agonistas dos Receptores de GABA-B/administração & dosagem , Masculino , Camundongos , Morfina/efeitos adversos , Naloxona/administração & dosagem , Naloxona/uso terapêutico , Antagonistas de Entorpecentes/administração & dosagem , Antagonistas de Entorpecentes/uso terapêutico , Fatores Sexuais , Síndrome de Abstinência a Substâncias/metabolismoRESUMO
The nicotine (NIC) withdrawal syndrome is considered to be a major cause of the high relapse rate among individuals undergoing smoking cessation. The aim of the present study was to evaluate a possible role of GABAB receptors in NIC withdrawal, by comparing GABAB1 knockout mice and their wild-type littermates. We analysed the time course of the global withdrawal score, the anxiety-like effects, monoamine concentrations, the brain-derived neurotrophic factor (BDNF) expression, the corticosterone plasmatic levels and [(3)H]epibatidine binding sites during NIC withdrawal precipitated by mecamylamine, a nicotinic receptor antagonist (MEC). In NIC withdrawn wild-type mice, we observed a global withdrawal score, an anxiety-like effect in the elevated plus maze, a decrease of the striatal dopamine and 3,4-dihydroxyphenylacetic acid concentrations, an increase of corticosterone plasma levels, a reduction of BDNF expression in several brain areas and an increase of [(3)H]epibatidine binding sites in specific brain regions. Interestingly, the effects found in NIC withdrawn wild-type mice were absent in GABAB1 knockout mice, suggesting that GABAB1 subunit of the GABAB receptor is involved in the regulation of the behavioural and biochemical alterations induced by NIC withdrawal in mice. These results reveal an interaction between the GABAB receptors and the neurochemical systems through which NIC exerts its long-term effects.
Assuntos
Receptores de GABA-A/deficiência , Síndrome de Abstinência a Substâncias/fisiopatologia , Tabagismo/fisiopatologia , Animais , Ansiedade/fisiopatologia , Encéfalo/efeitos dos fármacos , Encéfalo/fisiopatologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Corticosterona/sangue , Modelos Animais de Doenças , Masculino , Mecamilamina/farmacologia , Camundongos Endogâmicos BALB C , Camundongos Knockout , Nicotina/farmacologia , Agonistas Nicotínicos/farmacologia , Antagonistas Nicotínicos/farmacologia , Receptores de GABA-A/genética , Receptores Nicotínicos/metabolismo , Tabagismo/tratamento farmacológicoRESUMO
Previous studies from our laboratory showed that baclofen (BAC, GABAB receptor agonist) prevented the behavioral and neurochemical alterations of nicotine (NIC) withdrawal syndrome. To further investigate the mechanisms underlying these effects, we analyzed the c-Fos and brain-derived neutrophic factor (BDNF) expression during NIC withdrawal and its prevention with BAC. Swiss-Webster mice received NIC (2.5 mg/kg, sc) four times daily, for 7 days. On the 8th day, NIC-treated mice received the nicotinic antagonist mecamylamine (MEC; 2 mg/kg, i.p.) 1 h after the last dose of NIC. A second group of NIC-treated mice received BAC (2 mg/kg, i.p.) prior to MEC administration. Thirty minutes after MEC, mice were sacrificed and the immunohistochemistry assays (c-Fos and BDNF) were performed at different anatomical levels. c-Fos expression decreased in the dentate gyrus of the hippocampus (DG) and the bed nucleus of the stria terminalis (BST), and increased in the habenular (Hb), accumbens shell (AcbSh) nuclei during NIC withdrawal. BAC re-established the modified c-Fos expression only in the DG, BST and AcbSh during NIC withdrawal. Conversely, BDNF expression decreased in the CA1 and CA3 area of the hippocampus, the Hb, and caudate putamen (CPu) during NIC withdrawal. Finally, BAC restored the decreased BDNF expression during NIC withdrawal in the CA1, CA3, Hb, and CPu. The results suggest a relationship between BAC's preventive effect of the expression of NIC withdrawal signs, and its ability to restore the changes in c-Fos and BDNF expression, observed in specific brain areas of NIC-withdrawn mice.
Assuntos
Baclofeno/farmacologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Nicotina/efeitos adversos , Agonistas Nicotínicos/farmacologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Síndrome de Abstinência a Substâncias/metabolismo , Animais , Baclofeno/uso terapêutico , Gânglios da Base/efeitos dos fármacos , Gânglios da Base/metabolismo , Fator Neurotrófico Derivado do Encéfalo/genética , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Mecamilamina/farmacologia , Camundongos , Agonistas Nicotínicos/uso terapêutico , Antagonistas Nicotínicos/farmacologia , Especificidade de Órgãos , Proteínas Proto-Oncogênicas c-fos/genética , Síndrome de Abstinência a Substâncias/prevenção & controleRESUMO
The aim of the present study was to evaluate the possible involvement of GABAB receptors in nicotine-induced hypolocomotion and antinociceptive effects in mice. Animals were exposed to nicotine only once. Acute nicotine hydrogen tartrate salt (3mg/kg; subcutaneous, s.c.) administration induced hypolocomotion and antinociceptive responses in the tail-immersion and the hot-plate tests. The effects of pretreatment with either the GABAB receptor agonist baclofen (1, 2 and 3mg/kg; intraperitoneal, i.p.) or GABAB receptor antagonist 2-hydroxysaclofen (0.25, 0.5 and 1mg/kg; i.p.) were evaluated on these behavioral nicotine responses. The GABAB receptor agonist, baclofen (3mg/kg, i.p.) abolished nicotine-induced antinociceptive effects in the tail-immersion and the hot-plate tests, but did not modify nicotine-induced hypolocomotion. In addition, the GABAB receptor antagonist, 2-hydroxysaclofen (1mg/kg, i.p.) increased nicotine-induced antinociceptive effects in the tail-immersion and the hot-plate tests, and abolished nicotine-induced hypolocomotion. The present results shed light that the GABAB receptor has an important role in mediating specific acute nicotine responses such as hypolocomotion and antinociception in mice.
Assuntos
Analgésicos/farmacologia , Baclofeno/análogos & derivados , Baclofeno/farmacologia , Agonistas dos Receptores de GABA-B/farmacologia , Antagonistas de Receptores de GABA-B/farmacologia , Atividade Motora/efeitos dos fármacos , Nicotina/farmacologia , Animais , Interações Medicamentosas , Masculino , CamundongosRESUMO
RATIONALE: Nicotine is a major active ingredient in tobacco and plays a major role in tobacco addiction. In rodents, repeated nicotine administration produces behavioral responses related to its addictive properties, such as reinforcing effects and physical dependence. OBJECTIVES: The aim of the present study was to evaluate the possible role of GABAB receptor in responses induced by repeated nicotine administration in Swiss Webster mice. RESULTS: Nicotine hydrogen tartrate salt (0.5 mg/kg, s.c.) administration induced rewarding properties in the conditioning place preference test. The GABAB receptor agonist, baclofen (3 mg/kg, i.p.) abolished the rewarding properties induced by nicotine hydrogen tartrate salt (0.5 mg/kg, s.c.). In addition, naloxone-precipitated nicotine withdrawal induced somatic manifestations, anxiety-like effects in the elevated plus maze test and dysphoric manifestations in the conditioned place aversion paradigm. Baclofen (2 and 3 mg/kg, i.p.) prevented the somatic manifestations and the anxiety-like effects associated with naloxone-precipitated nicotine withdrawal but not the dysphoric manifestations. CONCLUSIONS: These results showed that nicotine rewarding properties and negative aspects of nicotine withdrawal, such as anxiety-like effects and somatic manifestations, can be modulated by the GABAB receptor activity. This study now reveals a novel possible application of baclofen to develop new therapeutic strategies to achieve smoking cessation.
Assuntos
Baclofeno/farmacologia , Agonistas dos Receptores de GABA-B/farmacologia , Nicotina/administração & dosagem , Agonistas Nicotínicos/administração & dosagem , Recompensa , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Animais , Ansiedade/tratamento farmacológico , Ansiedade/fisiopatologia , Aprendizagem da Esquiva/efeitos dos fármacos , Aprendizagem da Esquiva/fisiologia , Condicionamento Psicológico/efeitos dos fármacos , Condicionamento Psicológico/fisiologia , Masculino , Camundongos , Movimento/efeitos dos fármacos , Movimento/fisiologia , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Receptores de GABA-B/metabolismo , Percepção Espacial/efeitos dos fármacos , Percepção Espacial/fisiologia , Síndrome de Abstinência a Substâncias/fisiopatologia , Tabagismo/tratamento farmacológicoRESUMO
Previous studies from our laboratory showed that anxiety-related responses induced by nicotine (NIC), measured by the elevated plus maze, were abolished by 2-OH-saclofen (GABAB receptor antagonist) (1 mg/kg; ip) or the lack of GABAB receptors (GABAB1 knockout mice). Based on these behavioral data, the aims of the present study were: 1) to evaluate the possible neurochemical changes (dopamine, DA, serotonin, 5-HT, 3,4-dihydroxyphenylacetic acid, DOPAC, 5-hydroxyindoleacetic acid, 5-HIAA and noradrenaline, NA) and the c-Fos expression induced by the anxiolytic (0.05 mg/kg) or anxiogenic (0.8 mg/kg) doses of NIC in the dorsal raphe (DRN) and lateral septal (LSN) nucleus; 2) to study the possible involvement of GABAB receptors on the neurochemical alterations and c-Fos expression induced by NIC (0.05 and 0.8 mg/kg), using both pharmacological (2-OH-saclofen) and genetic (mice GABAB1 knockout) approaches. The results revealed that in wild-type mice, NIC (0.05 mg/kg) increased the concentration of 5-HT and 5-HIAA (p < 0.05) in the DRN, and NIC (0.8 mg/kg) increased the levels of 5-HT (p < 0.01) and NA (p < 0.05) in the LSN. Additionally, 2-OH-saclofen pretreatment (1 mg/kg, ip) or the lack of GABAB receptors abolished these neurochemical changes induced by NIC (p < 0.01, p < 0.05, respectively). On the other hand, NIC 0.05 and 0.8 mg/kg increased (p < 0.01) the c-Fos expression in the DRN and LSN respectively, in wild-type mice. In addition, 2-OH-saclofen pretreatment (1 mg/kg, ip) or the lack of GABAB receptors prevented the c-Fos alterations induced by NIC (p < 0.01). In summary, both approaches show that GABAB receptors would participate in the modulation of anxiolytic- and anxiogenic-like responses induced by NIC, suggesting the potential therapeutic target of these receptors for the tobacco addiction treatment.
Assuntos
Ansiedade/tratamento farmacológico , Baclofeno/análogos & derivados , Antagonistas de Receptores de GABA-B/uso terapêutico , Neurotransmissores/metabolismo , Receptores de GABA-B/genética , Receptores de GABA-B/metabolismo , Análise de Variância , Animais , Ansiedade/induzido quimicamente , Ansiedade/genética , Baclofeno/uso terapêutico , Modelos Animais de Doenças , Núcleo Dorsal da Rafe/efeitos dos fármacos , Núcleo Dorsal da Rafe/metabolismo , Relação Dose-Resposta a Droga , Regulação da Expressão Gênica/efeitos dos fármacos , Masculino , Camundongos , Camundongos Knockout , Nicotina/toxicidade , Agonistas Nicotínicos/toxicidade , Proteínas Proto-Oncogênicas c-fos/metabolismo , Núcleos Septais/efeitos dos fármacos , Núcleos Septais/metabolismoRESUMO
A previous study from our laboratory showed that baclofen (BAC, GABAB receptor agonist) was able to prevent the behavioral expression of nicotine (NIC) withdrawal syndrome. To further investigate the mechanisms underlying this effect, we conducted this study, with the aims of analyzing α4ß2 nicotinic receptor density during NIC withdrawal and, in case we found any changes, of determining whether they could be prevented by pretreatment with BAC. Swiss Webster albino mice received NIC (2.5 mg/kg, s.c.) 4 times daily, for 7 days. On the 8th day, NIC-treated mice received the nicotinic antagonist mecamylamine (MEC; 2 mg/kg, i.p.) 1 h after the last dose of NIC. A second group of NIC-treated mice received BAC (2 mg/kg, i.p.) prior to MEC administration. Thirty minutes after MEC, mice were sacrificed and brain autoradiography with [(3)H]epibatidine was carried out at five different anatomical levels. Autoradiographic mapping showed a significant increase of α4ß2 nicotinic receptor labeling during NIC withdrawal in the nucleus accumbens shell (AcbSh), medial habenular nucleus (HbM), thalamic nuclei, dorsal lateral geniculate (DLG) nucleus, fasciculus retroflexus (fr), ventral tegmental area, interpeduncular nucleus and superior colliculus. BAC pretreatment prevented the increased α4ß2 nicotinic receptor binding sites in the AcbSh, MHb, thalamic nuclei, DLG nucleus and fr. The present results suggest a relationship between BAC's preventive effect of the expression of NIC withdrawal signs, and its ability to restore the changes in α4ß2 nicotinic receptor labeling, evidenced in specific brain areas in NIC withdrawn animals.
Assuntos
Baclofeno/uso terapêutico , Agonistas dos Receptores de GABA-B/uso terapêutico , Mecamilamina/uso terapêutico , Antagonistas Nicotínicos/uso terapêutico , Receptores Nicotínicos/metabolismo , Tabagismo , Análise de Variância , Animais , Autorradiografia , Baclofeno/farmacologia , Encéfalo/diagnóstico por imagem , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Colinérgicos/farmacocinética , Modelos Animais de Doenças , Esquema de Medicação , Agonistas dos Receptores de GABA-B/farmacologia , Masculino , Mecamilamina/farmacologia , Camundongos , Antagonistas Nicotínicos/farmacologia , Cintilografia , Fatores de Tempo , Tabagismo/tratamento farmacológico , Tabagismo/metabolismo , Tabagismo/prevenção & controle , Trítio/farmacocinéticaRESUMO
In previous studies, we have reported sex-related differences during morphine withdrawal. We have also shown that the GABA(B) agonist baclofen (BAC) was able to prevent the morphine withdrawal syndrome in male as well as in female mice. Considering that early gene expression is induced by drugs of abuse, we evaluated the expression of c-Fos in several brain areas, in mice of either sex during naloxone (NAL)-precipitated withdrawal, and after pretreatment with BAC. Swiss-Webster prepubertal mice were rendered dependent by i.p. injection of morphine (2 mg/kg), twice daily for 9 days. On the 10th day, dependent mice were divided into two groups: the withdrawal group received NAL (6 mg/kg, i.p.) after the last dose of morphine, while the prevention group received BAC (2 mg/kg, i.p.) before NAL. Thirty minutes after NAL, animals were sacrificed by transcardial perfusion. Brains were removed and slices were obtained to perform immunohistochemical studies. Our results show a significant decrease in c-Fos expression in hippocampal dentate gyrus, CA3, and CA1 areas of morphine withdrawn males, vs. their control group. Conversely, in females, the number of c-Fos positive nuclei was not modified in any of the areas studied. BAC pretreatment had no effect on the decreased c-Fos expression in morphine withdrawn males. The sexual dimorphism observed here confirms the greater sensitivity of males over females in their response to morphine. The preventive action of BAC on the expression of morphine withdrawal would not be related to an effect on c-Fos expression.
Assuntos
Baclofeno/farmacologia , Agonistas dos Receptores de GABA-B/farmacologia , Hipocampo/efeitos dos fármacos , Morfina/toxicidade , Proteínas Proto-Oncogênicas c-fos/metabolismo , Síndrome de Abstinência a Substâncias/metabolismo , Animais , Feminino , Hipocampo/metabolismo , Masculino , Camundongos , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Fatores Sexuais , Síndrome de Abstinência a Substâncias/prevenção & controleRESUMO
Nicotine is the main active component of tobacco, and has both acute and chronic pharmacological effects that can contribute to its abuse potential in humans. The aim of the present study was to evaluate a possible role of GABA(B) receptors in acute and chronic responses to nicotine administration, by comparing GABA(B1) knockout mice and their wild-type littermates. In wild-type mice, acute nicotine administration (0.5, 1, 3 and 6 mg/kg, sc) dose-dependently decreased locomotor activity, and induced antinociceptive responses in the tail-immersion and hot-plate tests. In GABA(B1) knockout mice, the hypolocomotive effect was observed only with the highest dose of nicotine, and the antinociceptive responses in both tests were significantly reduced in GABA(B1) knockout mice compared to their wild-type littermate. Additionally, nicotine elicited anxiolytic- (0.05 mg/kg) and anxiogenic-like (0.8 mg/kg) responses in the elevated plus-maze test in wild-type mice, while selectively the anxiolytic-like effect was abolished in GABA(B1) knockout mice. We further investigated nicotine withdrawal in mice chronically treated with nicotine (25 mg/kg/day, sc). Mecamylamine (1 mg/kg, sc) precipitated several somatic signs of nicotine withdrawal in wild-type mice. However, signs of nicotine withdrawal were missing in GABA(B1) knockout mice. Finally, there was a decreased immunoreactivity of Fos-positive nuclei in the bed nucleus of the stria terminalis, basolateral amygdaloid nucleus and hippocampal dentate gyrus in abstinent wild-type but not in GABA(B1) knockout mice. These results reveal an interaction between the GABA(B) system and the neurochemical systems through which nicotine exerts its acute and long-term effects.
Assuntos
Estimulantes Ganglionares/toxicidade , Atividade Motora/efeitos dos fármacos , Nicotina/toxicidade , Agonistas Nicotínicos/toxicidade , Receptores de GABA-B/metabolismo , Tabagismo/fisiopatologia , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/metabolismo , Tonsila do Cerebelo/patologia , Analgésicos não Narcóticos/administração & dosagem , Analgésicos não Narcóticos/toxicidade , Animais , Ansiolíticos/administração & dosagem , Ansiolíticos/toxicidade , Ansiedade/induzido quimicamente , Comportamento Animal , Giro Denteado/efeitos dos fármacos , Giro Denteado/metabolismo , Giro Denteado/patologia , Relação Dose-Resposta a Droga , Bloqueadores Ganglionares/administração & dosagem , Bloqueadores Ganglionares/farmacologia , Estimulantes Ganglionares/administração & dosagem , Estimulantes Ganglionares/antagonistas & inibidores , Injeções Subcutâneas , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Nicotina/administração & dosagem , Nicotina/antagonistas & inibidores , Agonistas Nicotínicos/administração & dosagem , Agonistas Nicotínicos/química , Antagonistas Nicotínicos/administração & dosagem , Antagonistas Nicotínicos/farmacologia , Limiar da Dor/efeitos dos fármacos , Receptores de GABA-B/genética , Núcleos Septais/efeitos dos fármacos , Núcleos Septais/metabolismo , Núcleos Septais/patologia , Tabagismo/metabolismoRESUMO
The aim of the present study was to evaluate the possible involvement of GABA(B) receptors in the anxiolytic- and anxiogenic-like responses induced by nicotine in mice. Animals were exposed to nicotine only once. The acute administration of low (0.05mg/kg, sc) or high (0.8mg/kg, sc) doses of nicotine produced opposite effects in the elevated plus maze test; respectively, anxiolytic- and anxiogenic-like responses. The effect of pretreatment with either the GABA(B) receptor antagonist 2-OH-saclofen (0.25, 0.5 and 1mg/kg; ip) or the GABA(B) receptor agonist baclofen (0.5, 1 and 2mg/kg; ip), was evaluated on the anxiolytic- and anxiogenic-like responses induced by nicotine. 2-OH-saclofen completely abolished both nicotine-induced effects (p<0.001) at the highest dose tested, suggesting an involvement of GABA(B) receptors in these behavioural responses. On the other hand, baclofen failed to modify the anxiety-related effects of nicotine. These results suggest that the GABA(B) receptors are involved in the regulation of nicotine-induced anxiety-related behavioural responses in mice, and provide new findings to support a potential pharmaco therapeutic use of GABAergic drugs in the treatment of tobacco addiction.
Assuntos
Ansiedade/etiologia , Ansiedade/fisiopatologia , Nicotina/toxicidade , Receptores de GABA-B/fisiologia , Animais , Ansiolíticos/farmacologia , Ansiedade/psicologia , Baclofeno/análogos & derivados , Baclofeno/farmacologia , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Agonistas dos Receptores de GABA-B/farmacologia , Antagonistas de Receptores de GABA-B/farmacologia , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Camundongos , Atividade Motora/efeitos dos fármacos , Tabagismo/tratamento farmacológico , Tabagismo/fisiopatologiaRESUMO
BACKGROUND: Nicotine (NIC), the major active component of tobacco, is critical in the maintenance of the smoking habit. The aims of the present study were to analyze the behavioural and neurochemical variations during NIC withdrawal syndrome in mice, and whether they are prevented with baclofen (BAC, GABA(B) receptor agonist). METHODS: Swiss-Webster albino mice received NIC (2.5 mg/kg, s.c.) 4 times daily, for 7 consecutive days. On day 8 (the day of the experiment), NIC-treated mice received the nicotine antagonist mecamylamine (MEC, 2 mg/kg, i.p.) 1h after the last dose of NIC. A second group of dependent mice received BAC (2mg/kg, i.p.) before MEC-precipitated abstinence. The somatic signs were measured for 30 min. Dopamine (DA), serotonin (5-hydroxytryptamine; 5-HT) and its metabolites concentrations were determined by HPLC in the striatum, cortex and hippocampus. RESULTS: The global score was greater in the abstinent group compared to the control group. Moreover, the global score time course showed a higher increase at 10 min compared to the global score at 5 min or 30 min after MEC-precipitated NIC withdrawal. In addition, the global score was attenuated by BAC. The DA and dihydroxyphenyl acetic acid (DOPAC) cortical levels decreased in the abstinent group, while BAC reestablished these levels 10 min after NIC withdrawal. Furthermore, DA and 5-HT striatal levels decreased during NIC withdrawal, and BAC reverted this decrease. CONCLUSION: In conclusion, the prevention of NIC withdrawal signs by BAC could be related to changes in dopaminergic and serotonergic activity.
Assuntos
Baclofeno/farmacologia , Mecamilamina/efeitos adversos , Nicotina/efeitos adversos , Agonistas Nicotínicos/efeitos adversos , Antagonistas Nicotínicos/efeitos adversos , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Síndrome de Abstinência a Substâncias/prevenção & controle , Animais , Baclofeno/sangue , Baclofeno/uso terapêutico , Comportamento Animal/efeitos dos fármacos , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos , Masculino , Mecamilamina/sangue , Camundongos , Atividade Motora/efeitos dos fármacos , Nicotina/sangue , Agonistas Nicotínicos/sangue , Antagonistas Nicotínicos/sangue , Abandono do Hábito de Fumar/métodos , Síndrome de Abstinência a Substâncias/metabolismo , Fatores de TempoRESUMO
It has been shown that the expression of the morphine (MOR) withdrawal syndrome precipitated by naloxone (NAL) is more intense in male mice than in females, but the reasons for this phenomenon remain uncertain. The purpose of the present study was to evaluate whether this sexual dimorphism might be due to differences in MOR and/or NAL plasma levels after a chronic treatment with MOR. Prepubertal Swiss male and female mice were rendered dependent by intraperitoneal (i.p.) injection of MOR (2 mg/kg), twice daily for 9 days. On day 10 dependent mice received NAL (6 mg/kg, i.p.) 60 min after MOR injection. Blood samples were taken at different times in order to determine MOR and NAL plasma levels by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC), respectively. Pharmacokinetic analysis showed no differences between male and female mice either for MOR or for NAL. In conclusion, although males and females respond differentially to NAL-precipitated withdrawal, this dimorphic behavior would not be influenced by a pharmacokinetic factor.
Assuntos
Morfina/farmacocinética , Naloxona/farmacocinética , Síndrome de Abstinência a Substâncias/metabolismo , Analgésicos Opioides/administração & dosagem , Analgésicos Opioides/farmacocinética , Animais , Área Sob a Curva , Cromatografia Líquida de Alta Pressão , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Meia-Vida , Injeções Intraperitoneais , Masculino , Camundongos , Morfina/administração & dosagem , Dependência de Morfina/sangue , Dependência de Morfina/complicações , Naloxona/administração & dosagem , Naloxona/sangue , Antagonistas de Entorpecentes/administração & dosagem , Antagonistas de Entorpecentes/farmacocinética , Fatores Sexuais , Maturidade Sexual , Síndrome de Abstinência a Substâncias/etiologia , Fatores de TempoRESUMO
Although the expression of the morphine (MOR) withdrawal syndrome is more marked in male mice than in females, we have demonstrated that the GABAB agonist baclofen (BAC) is able to attenuate MOR withdrawal signs in either sex. In order to extend these previous observations, the aim of the present study was to evaluate the mu-opioid receptor labeling in various brain areas in mice of either sex, during MOR withdrawal and its prevention with BAC. Prepubertal Swiss-Webster mice were rendered dependent by intraperitonial (i.p.) injection of MOR (2 mg/kg) twice daily for 9 days. On the 10th day, dependent animals received naloxone (NAL; 6 mg/kg, i.p.) 60 min after MOR, and another pool of dependent mice received BAC (2 mg/kg, i.p.) previous to NAL. Thirty minutes after NAL, mice were sacrificed and autoradiography with [3H]-[D-Ala2, N-Me-Phe4, -glycol5] enkephalin (DAMGO) was carried out on mice brains at five different anatomical levels. Autoradiographic mapping showed a significant increase of mu-opioid receptor labeling during MOR withdrawal in nucleus accumbens core (NAcC), caudate putamen (CPu), mediodorsal thalamic nucleus (MDTh), basolateral and basomedial amygdala, and ventral tegmental area vs. respective control groups in male mice. In contrast, opiate receptor labeling was not significantly modified in any of the brain areas studied in withdrawn females. BAC reestablished mu-opioid receptor binding sites during MOR withdrawal only in NAcC of males, and a similar tendency was observed in CPu and MDTh, even when it was not statistically significant. The sexual dimorphism observed in the present study confirms previous reports indicating a greater sensitivity of males in response to MOR pharmacological properties. The present results suggest that the effect of BAC in preventing the expression of MOR withdrawal signs could be related with the ability of BAC to reestablish the mu-opioid receptor labeling in certain brain areas.
Assuntos
Baclofeno/farmacologia , Dependência de Morfina/tratamento farmacológico , Morfina/efeitos adversos , Receptores Opioides mu/efeitos dos fármacos , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Envelhecimento/metabolismo , Animais , Autorradiografia , Baclofeno/uso terapêutico , Sítios de Ligação/efeitos dos fármacos , Sítios de Ligação/fisiologia , Encéfalo/anatomia & histologia , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Modelos Animais de Doenças , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , Feminino , Agonistas GABAérgicos/farmacologia , Agonistas GABAérgicos/uso terapêutico , Masculino , Camundongos , Dependência de Morfina/metabolismo , Dependência de Morfina/fisiopatologia , Antagonistas de Entorpecentes/farmacologia , Entorpecentes/efeitos adversos , Receptores Opioides mu/metabolismo , Caracteres Sexuais , Síndrome de Abstinência a Substâncias/metabolismo , Síndrome de Abstinência a Substâncias/fisiopatologiaRESUMO
Morphine (MOR) withdrawal signs are more marked in males than in females. Considering that the influence of the dopaminergic system on these differences is unclear, we analyzed dopamine (DA) and dihydroxyphenylacetic-acid (DOPAC) brain levels during naloxone (NAL)-precipitated withdrawal as well as the involvement of D(1) and D(2) receptors in the expression of MOR withdrawal in either sex. Prepubertal Swiss-Webster mice received MOR (2 mg/kg, i.p.) twice daily for 9 days. On the tenth day, dependent animals received NAL (6 mg/kg, i.p.) after MOR and were sacrificed 30 min later. DA and DOPAC concentrations were determined in different brain areas using HPLC with electrochemical detection. Other pool of mice received either a D(1) (SCH 23390; 0.2 mg/kg, i.p.) or D(2) (raclopride; 0.3 mg/kg, i.p.) receptor antagonist before NAL and withdrawal signs were evaluated. DA and DOPAC levels only decreased in striatum and cortex of withdrawn males. Conversely, both DA receptor antagonists decreased the expression of MOR withdrawal signs in either sex. The neurochemical sex differences described here could partially explain the behavioral sex differences observed during MOR withdrawal. Additionally, SCH-23390 and raclopride effects suggest an important role of both DA receptors in the expression of MOR withdrawal in males and females.
Assuntos
Dopamina/fisiologia , Morfina/efeitos adversos , Síndrome de Abstinência a Substâncias/fisiopatologia , Animais , Comportamento Animal , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Feminino , Masculino , Camundongos , Receptores de Dopamina D1/fisiologia , Receptores de Dopamina D2/fisiologia , Maturidade Sexual/fisiologia , Síndrome de Abstinência a Substâncias/metabolismoRESUMO
We have previously shown that the GABA(B) agonist baclofen (BAC) prevents the expression of morphine (MOR) withdrawal syndrome in male as well as female mice. In addition, we have demonstrated that BAC reestablishes the dopamine levels modified by MOR withdrawal syndrome in male mice. The aim of the present study was to evaluate the micro-opioid receptor binding parameters in striatum and frontal cortex of male and female mice during MOR withdrawal and its prevention with BAC. Prepubertal Swiss-Webster mice of either sex were rendered dependent by intraperitoneal (i.p.) injection of MOR (2 mg/kg) twice daily for 9 days. On the tenth day, dependent animals received naloxone (NAL) (6 mg/kg, i.p.) 60 min after the last dose of MOR and another pool of dependent mice received BAC (2 mg/kg, i.p.) previous to NAL injection. Thirty min after NAL or saline injection mice were sacrificed, brains were collected, and the striatum and frontal cortex were dissected in order to perform binding studies with [(3)H][DAMGO]. The density of micro-opioid receptor increased significantly during MOR withdrawal in male and female striatum as well as in male cortex. In addition, in both brain areas the B(max) was higher in male than in female mice during MOR withdrawal. Finally, BAC pretreatment of MOR withdrawn mice reestablished the levels of micro-opioid receptor by significantly decreasing the B(max) in either sex. In conclusion, although there were sex differences in the micro-opioid receptor density during MOR withdrawal syndrome, BAC was able to reestablish the changes in binding parameters induced by the NAL-precipitated withdrawal in female and male mice.
Assuntos
Baclofeno/farmacologia , Agonistas GABAérgicos/farmacologia , Entorpecentes/farmacologia , Receptores Opioides mu/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Ala(2)-MePhe(4)-Gly(5)-Encefalina , Feminino , Masculino , Camundongos , Morfina/farmacologia , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Fatores Sexuais , Síndrome de Abstinência a Substâncias/tratamento farmacológicoRESUMO
The present study analyzes the effects of baclofen (BAC) on mice brain neurochemical alterations during the morphine (MOR) withdrawal syndrome. Male Swiss-Webster albino mice (27-33 g) were rendered dependent by intraperitoneal (i.p.) injection of MOR (2mg/kg), twice daily for 9 days. On day 10, the dependent animals were divided into two groups: one receiving naloxone (NAL; 6 mg/kg i.p.) to precipitate the withdrawal syndrome 60 min after the last dose of MOR and the other received BAC (2mg/kg, i.p.) followed by NAL (6 mg/kg, i.p.), injected 30 and 60 min after the last dose of MOR, respectively. Ten minutes after these treatments, mice were killed by decapitation and the striatum, cortex and hippocampus were dissected to determine endogenous concentrations of dopamine (DA), 5-hydroxytryptamine (5-HT) and their metabolites using HPLC with electrochemical detection. Striatal DA, dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid (HVA) concentrations as well as cortical DA concentrations of the withdrawal groups decreased significantly with respect to the control groups. BAC attenuated the decrease in DA and DOPAC concentrations observed during the withdrawal, without modifying per se the control DA concentrations. No changes on 5-HT and its metabolite 5-hydroxyindolacetic acid (5-HIAA) concentrations were observed during the MOR abstinence syndrome. The prevention caused by BAC on the decreased concentrations of DA induced by MOR withdrawal could have a therapeutic interest for the management of withdrawal syndrome.
Assuntos
Baclofeno/farmacologia , Córtex Cerebral/metabolismo , Dopamina/metabolismo , Agonistas GABAérgicos/farmacologia , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Neostriado/metabolismo , Síndrome de Abstinência a Substâncias/metabolismo , Animais , Córtex Cerebral/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Eletroquímica , Agonistas dos Receptores de GABA-B , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Ácido Homovanílico/metabolismo , Ácido Hidroxi-Indolacético/metabolismo , Masculino , Camundongos , Dependência de Morfina/fisiopatologia , Neostriado/efeitos dos fármacos , Serotonina/metabolismoRESUMO
The aim of this study was the development of a pharmacokinetic-pharmacodynamic (PK/PD) model of the antinociceptive effect of baclofen in mice. We studied the dose response curve of the analgesic action of baclofen in mice by hot plate test. Baclofen produced a dose dependent antinociceptive effect with doses between 1-3 mg/kg administered intraperitoneally (i.p.) (ED50: 1.94 mg/kg of racemate) and this effect fits to a linear pharmacodynamic model. Blood and brain concentrations of (-)3H-baclofen were determined by Thin-Layer Chromatography (TLC) and counted in the scintillation-counter. The PK/PD models were analyzed with the PC-TOPFIT V.2.0 and the tests for distinguishing between models were several adjustment parameters as Akaike information criterion (AIC), Imbimbo criterion (Ip), standard deviation (SD) and the correlation coefficient (r2). Accordingly with these adjustment parameters, a 2 compartment open model was selected where plasma is the central compartment and brain is in the peripheral compartment. In this model, the effect is linked to the peripheral compartment. When the antinociceptive effect of baclofen was plotted against blood concentration, the resulting curve exhibited an anticlockwise hysteresis loop, but on the other hand, when the antinociceptive effect was plotted against the brain concentration, the hysteresis was collapsed. These results confirmed the selected model in our study, as the best adjustment was shown when the pharmacological response was linked to the peripheral compartment.