Effect of pentobarbital anesthesia on serotonin metabolism in hypoxic rat brain.

Two hours of pentobarbital anesthesia resulted in marked elevation of serotonin (5-HT) level and decreased accumulation of 5-hydroxyindolacetic acid (5-HIAA) after probenecid, in specific parts of rat brain. In hypoxia, either no change (cortex, hypothalamus) or an increase (striatum, pons with medulla) in 5-HT content was observed. Concomitantly, the decrease of 5-HIAA level and its accumulation after transport inhibition occured. Pentobarbital pretreatment of hypoxic rats resulted in further diminution of 5-HT degradation after probenecid, having synergistic character in pons with medulla, which points to the specific sensitivity of serotonergic system in the latter area. Hypoxia-induced decrease of 5-HIAA level was prevented by pentobarbital pretreatment. The possible participation of 5-HIAA efflux inhibition in this phenomenon is discussed.