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 5% and 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 5% group showed significative decrease of mean arterial pressure compared to ETOH 0% and an increase of heart rate compared to ETOH 0% and 20% groups. The sensitivity (gain) of baroreceptor reflex was significantly attenuated in ETOH 5% withdrawn animals and in ETOH 5% and 20% animals nonwithdrawn. This was mainly due to the reduction of range of the baroreflex and changes in the bradycardia and tachycardia plateau. The nonwithdrawn ETOH 5% group 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.