DIFFERENTIAL-EFFECTS OF ANESTHETICS ON SYMPATHETIC-NERVE ACTIVITY ANDARTERIAL BARORECEPTOR REFLEX IN CHRONICALLY INSTRUMENTED RATS

The effects of pentobarbital sodium, chloralose, and urethane on sympa thetic nerve activity and arterial baroreceptor reflex were examined u sing rats chronically instrumented for recordings of blood pressure (B P), electrocardiogram and renal sympathetic nerve activity (RSNA). Pen tobarbital sodium (30 mg/kg, i.v.) produced a decrease in BP with a tr ansient decrease in heart rate (HR) and no change in RSNA. Chloralose (50 mg/kg, i.v.) also caused a decrease in BP and no change in HR and RSNA until a later increase in HR and RSNA, while urethane (800 mg/kg, i.v.) increased BP, HR, and RSNA. Baroreceptor reflex function was as sessed by constructing a logistic function curve compiled from data ob tained by intravenous infusion in increasing doses of phenylephrine an d sodium nitroprusside. Both pentobarbital sodium and chloralose admin istration decreased the gain of baroreceptor reflex control of both HR and RSNA. Urethane also decreased the gain of baroreceptor reflex con trol of HR but elicited no change in that of RSNA. These results sugge st that different intravenously administered anesthetics affect the pe ripheral sympathetic outflows in qualitatively and quantitatively diff erent manners. (C) 1998 Elsevier Science B.V. All rights reserved.