RESUMO
Gamma-aminobutyric acid (GABA) transporter subtype 1 (GAT1), which transports extracellular GABA into presynaptic neurons, plays an important regulatory role in the function of GABAergic systems. However, the contributions of the GAT1 in regulating mental status are not fully understood. In this paper, we observed the behavioral alterations of GAT1 knockout (GAT1(-/-)) mice using several depression- and anxiety-related models (eg, the forced-swimming test and the tail-suspension test for testing depression-related behaviors; the open-field test, the dark-light exploration test, the emergence test, and the elevated plus maze (EPM) test for anxiety-related behaviors). Here we found that GAT1(-/-) mice showed a lower level of depression- and anxiety-like behaviors in comparison to wild-type mice. Furthermore, GAT1(-/-) mice exhibited measurable insensitivity to selected antidepressants and anxiolytics such as fluoxetine, amitriptyline, buspirone, diazepam, and tiagabine in the tail-suspension test and/or the EPM test. Moreover, the basal level of corticosterone was found to be significantly lower in GAT1(-/-) mice. These results showed that the absence of GAT1 affects mental status through enhancing the GABAergic system, as well as modifying the serotonergic system and the hypothalamic-pituitary-adrenal (HPA) activity in mice.
Assuntos
Transtornos de Ansiedade/metabolismo , Encéfalo/metabolismo , Transtorno Depressivo/metabolismo , Proteínas da Membrana Plasmática de Transporte de GABA/genética , Ácido gama-Aminobutírico/metabolismo , Animais , Ansiolíticos/farmacologia , Antidepressivos/farmacologia , Transtornos de Ansiedade/genética , Transtornos de Ansiedade/fisiopatologia , Comportamento Animal/fisiologia , Encéfalo/fisiopatologia , Química Encefálica/genética , Corticosterona/sangue , Corticosterona/metabolismo , Transtorno Depressivo/genética , Transtorno Depressivo/fisiopatologia , Resistência a Medicamentos/genética , Feminino , Proteínas da Membrana Plasmática de Transporte de GABA/deficiência , Sistema Hipotálamo-Hipofisário/metabolismo , Sistema Hipotálamo-Hipofisário/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Testes Neuropsicológicos , Serotonina/metabolismo , Estresse Psicológico/metabolismo , Estresse Psicológico/fisiopatologiaRESUMO
It is widely accepted that the GABAergic system plays an important role in the action of ethanol in vivo. GABA transporter subtype 1 (GAT1) constructs high affinity reuptake sites in the CNS and regulates GABAergic transmissions. In this study, mice lacking the GAT1 were developed by homologous recombination. Both hetero- and homozygous GAT1 mutant mice were tested for ethanol, saccharin or quinine consumption, ethanol-conditioned place preference, ethanol-conditioned taste aversion, ethanol-simulated motor activity, and ethanol-induced sedation/hypnosis. The GAT1(-/-) mice showed decreased ethanol aversion and ethanol reward, and insensitivity to both the sedative/hypnotic and the motor stimulant effects of ethanol, along with increased avoidance of quinine preference and consumption. GAT1(+/-) mice showed significantly increased consumption of ethanol and saccharin, however, enhanced the rewarding and preference effect of ethanol, increased avoidance of quinine, and higher sensitivity to the motor stimulant effect of ethanol. These results demonstrate that GAT1, perhaps in a bi-directional way, modulates some behavioral effects of ethanol. The GAT1 mutant mice provided us a very useful model to investigate the mechanisms of ethanol action in vivo.
