EFFECTS OF ANESTHETICS ON NOREPINEPHRINE RELEASE IN THE HYPOTHALAMIC PARAVENTRICULAR NUCLEUS REGION OF AWAKE RATS

The effects of pentobarbital sodium, chloralose and urethane on norepi nephrine (NE) release in the hypothalamic paraventricular nucleus (PVN ) region were examined in awake rats. An in vivo microdialysis method was used. Extracellular NE concentrations in the PVN region were measu red by high performance liquid chromatography with electrochemical det ection. Pentobarbital sodium (30 mg/kg, intravenously (i.v.)) and chlo ralose (50 mg/kg, i.v.) caused a 30-40% decrease in NE release while u rethane (800 mg/kg, i.v.) caused a 50% increase. Plasma NE concentrati on was not altered after pentobarbital sodium and chloralose administr ations, except for its increase in chloralose at 5 h, white the concen tration increased significantly (P < 0.01) after urethane. These resul ts suggest that, in the rat, these anesthetic agents have different ef fects on noradrenergic activity in the PVN region as well as on plasma NE. (C) 1998 Elsevier Science ireland Ltd.