Attenuation of the baroreceptor reflex by general anesthetic agents in the normotensive rat

We have investigated the effects of urethane, a urethane + allobarbital mixture, alpha-chloralose and sodium pentobarbital on baroreceptor reflex function in the normotensive rat. Results were compared to those obtained in the conscious rat. Baroreceptor reflex function was evaluated from the fall in heart rate which accompanied the rise in diastolic arterial pressure following intravenous administration of phenylephrine. All four anesthetic agents attenuated reflex function as shown by a decrease in the bradycardiac response. There was a four to five-fold attenuation with urethane and urethane + allobarbital and a two- to three-fold attenuation with alpha-chloralose and sodium pentobarbital.