[Propofol suppresses sympathetic activity and inhibits the baroreceptor reflex in waking rats]

The effects of propofol on sympathetic nerve activity and on the baroreceptor reflexes were examined in male Wistar rats. Sympathetic nerve activity was recorded directly from a renal nerve electrode placed earlier; baroreceptor reflex activity was estimated by changes in blood pressure (BP) and heart rate (HR) induced by the vasopressor phenylephrine, or the vasodilator, nitroprusside. Awake animals were anesthetized with propofol (10 mg/kg iv bolus, followed by approximately 35 mg/kg/hr by infusion) for 30 min. During the first 3 minutes, propofol increased sympathetic nerve activity by 113%, while mean arterial pressure was lowered to 85% of control. After 20 minutes, both sympathetic nerve activity and blood pressure had declined by 14% below baseline. Heart rate was stable at the level of approximately 110% throughout. Propofol also attenuated the sensitivity of chronotropic and sympathetic components of the baroreceptor reflex (i.e., to 23-43% and 25-34%, respectively). Thus, propofol lowers blood pressure by a central mechanism attenuating sympathetic nerve activity and sensitivity of baroreceptor reflex.