RESUMO
Transgenic rats with low brain angiotensinogen, TGR(ASrAOGEN)680, expressing an antisense RNA against angiotensinogen in glial cells, provide an interesting tool to evaluate the role of brain angiotensins in different behavior responses. The present study was conducted to test the hypothesis that angiotensin-(1-7) [Ang-(1-7)] and serotonin can modulate anxiety and depression-related behaviors in the TGR(ASrAOGEN)680 rats. Therefore, the effect of acute intracerebroventricular administration of Ang-(1-7) and intraperitoneal administration of the selective serotonin reuptake inhibitor fluoxetine was evaluated in TGR(ASrAOGEN) rats subjected to the elevated plus maze (EPM) and forced swimming (FST) tests. Transgenic rats spent a lower percentage of time in the open arms of EPM and showed a significant increase in the immobility time in FST, indicating that a low angiotensinogen level in the brain leads to anxiety-like behavior accompanied by a depression-like state. Administration of both, Ang-(1-7) and fluoxetine reversed the anxiety- and depressive-like behavior of transgenic rats with low brain angiotensinogen, suggesting that this may be, at least in part, related to a decreased level of Ang-(1-7) and serotonin in the brain of these animals.
Assuntos
Angiotensina I/uso terapêutico , Angiotensinogênio/metabolismo , Ansiedade/tratamento farmacológico , Encéfalo/metabolismo , Depressão/tratamento farmacológico , Fragmentos de Peptídeos/uso terapêutico , Psicotrópicos/uso terapêutico , Angiotensinogênio/genética , Animais , Ansiedade/genética , Encéfalo/efeitos dos fármacos , Depressão/genética , Modelos Animais de Doenças , Vias de Administração de Medicamentos , Fluoxetina/uso terapêutico , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , RNA Antissenso/genética , Ratos , Ratos Sprague-Dawley , Ratos Transgênicos , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Inibidores Seletivos de Recaptação de Serotonina/uso terapêutico , Natação/psicologiaRESUMO
Previous evidence indicates that a balance between inhibitory gabaergic and excitatory angiotensinergic factors in the PVN is important for cardiovascular control. We investigated the cardiovascular response evoked from activation or blockade of GABA(A) receptors in the paraventricular nucleus (PVN), in transgenic rats with low brain angiotensinogen [TGR(ASrAOGEN)]. Brain Ang II and Ang-(1-7) levels were also determined. In functional experiments, TGR(ASrAOGEN) and Sprague-Dawley rats (SD, control) were anesthetized with urethane and blood pressure (BP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were recorded. Brain Ang II and Ang-(1-7) levels were largely reduced in TGR(ASrAOGEN) compared with SD rats. Inhibition of PVN neurons with the GABA(A) agonist, muscimol (1 nmol/100 nL), resulted in an attenuated fall in all cardiovascular variables in TGR(ASrAOGEN) compared with SD rats. This difference was particularly pronounced in HR (TGR Mus -23±6 bpm vs. -77±9 bpm SD Mus; P<0.05) and RSNA (TGR -3±10% vs.-29±8% SD; P<0.05). Furthermore, the sympathetic response evoked by blockade of GABA(A) receptors in the PVN of TGR(ASrAOGEN) was also largely suppressed. The present data indicate that the sympathetic outflow mediated by PVN neurons under basal conditions is suppressed in TGR(ASrAOGEN) rats corroborating the functional significance of brain angiotensin production in the central regulation of sympathetic output to the cardiovascular system.