Pentobarbital anesthesia suppresses basal and 2-deoxy-D-glucose-stimulated plasma catecholamines

Abstract

Since pentobarbital anesthesia is known to attenuate certain autonomic reflexes, whether pentobarbital would suppress both basal and stimulated levels of plasma catecholamines and whether a large stimulus might counterbalance this suspected suppression was tested. In untrained dogs, sampled by venipuncture, pentobarbital (30 mg/kg i.v.) decreased the plasma concentration of epinephrine (E) from 146 .+-. 9 to 38 .+-. 8 (SE) pg/ml (n = 46) and norepinephrine (epinephrine, NE) from 276 .+-. 13 to 91 .+-. 10 pg/ml (both P < 0.0005), suggesting that barbiturate anesthesia suppresses sympathetic outflow in these mildly stressed animals. Pentobarbital also had a marked suppressive effect on the lower baseline catecholamines (E, 84 .+-. 14 pg/ml; NE, 118 .+-. 10 pg/ml; n = 6) of trained, chronically catheterized dogs, suggesting that it was capable of suppressing resting sympathetic outflow as well. To determine whether pentobarbital anesthesia also suppressed reflex activation of the sympathetic nervous system, the plasma catecholamine response to the neuroglucopenic agent, 2-deoxy-D-glucose (2-DG), was measured in conscious and in pentobarbital-anesthetized dogs. In conscious dogs, the administration of 2-DG (100 mg/kg i.v.) doubled the base-line plasma concentration of E and NE 30 min after the 2-DG injection. The administration of 2-DG (100 mg/kg i.v.) to pentobarbital-anesthetized dogs produced no significant increase of either plasma catecholamine, suggesting marked suppression of this sympathetic reflex. Increasing the dose of 2-DG 3-fold (300 mg/kg i.v.) produced increases of plasma E (.DELTA. = +159 .+-. 15 pg/ml) and NE (.DELTA. = +126 .+-. 28 pg/ml) in pentobarbital-anesthetized dogs that were similar to those observed in conscious dogs that had received the lower dose of 2-DG (100 mg/kg i.v.). Pentobarbital suppresses basal and stimulated sympathetic outflow and the contribution of the sympathetic nervous system may be masked by pentobarbital anesthesia unless the stimulus for reflex activation is large.