We investigated the acute effects of thiopental anesthesia (4 mg/100 g, i.v.) on plasma glucose, insulin, triacylglycerol, and prolactin levels in rats treated with bromocriptine (BR) (0.4 mg/100 g body wt, i.p., for two weeks). Thiopental anesthesia induced a rapid increase in plasma insulin that was more pronounced in the animals treated with BR (116%, P <0.05). Thiopental anesthesia also produced a 55% decreased in plasma prolactin levels (P <0.01) in control fed rats, and a 22% reduction in plasma triacylglycerol (P <0.05) in both controls and BR-treated rats. We conclude that BR may constitute and additional sympatholytic factor in animals submitted to thiopental anesthesia.