Efeitos da administração crônica do álcool sobre os mecanismos neurais de regulação da pressão arterial / Effect of Chronic Administration of Alcohol and its Withdrawal on the Neural Mechanisms of Arterial Blood Pressure Regulation

ABSTRACT

PURPOSE: This study evaluated the effect of alcohol and its withdrawal on arterial baroreflex (BR) and cardiopulmonary reflex (CPR). METHODS: Male Wistar rats (150-250g) distributed in three groups (10-19 animals in each): ETOH 0, ETOH 5and ETOH 20, received alcohol solution at the end of the day and at night over the week, and all day and night at the weekends for a 90 day period. The BR function was assessed analyzing the bradycardic response to phenylephrine-induced vasoconstriction and tachycardic response to sodium nitroprusside-induced vasodilatation. The CPR was evaluated through the simultaneous bradycardic and hypotensive responses to 5-hydroxytryptamine (5-HT). The tests were performed in conscious animals in conditions of alcohol intake or 48h alcohol withdrawal. RESULTS: The nonwithdrawn animals of ETOH 5group showed significative decrease of mean arterial pressure compared to ETOH 0and an increase of heart rate compared to ETOH 0and 20groups. The sensitivity (gain) of baroreceptor reflex was significantly attenuated in ETOH 5withdrawn animals and in ETOH 5and 20animals nonwithdrawn. This was mainly due to the reduction of range of the baroreflex and changes in the bradycardia and tachycardia plateau. The nonwithdrawn ETOH 5group showed a higher effect of 5-HT (around 50) on the fall of diastolic arterial pressure. CONCLUSION: These results suggest that alcohol intake produced significant alterations in the neural mechanisms of cardiovascular regulation that could result in a dysfunction of blood pressure regulation.