ALTERATIONS IN BRAIN REGIONAL MONOAMINE LEVELS AFTER CHRONIC ADMINISTRATION OF PHENOBARBITONE TO ADULT-RATS

This study was undertaken to find out if the mechanism of action of ph enobarbitone is mediated through monoamine alterations. Phenobarbitone (60 mg/kg body weight) was administered to adult male Wistar rats by intraperitoneal injections chronically for 45 days and the regional br ain levels of norepienephrine (NE), dopamine (DA) and serotonin (5-HT) were assayed using high performance liquid chromatographic (HPLC) met hod. The phenobarbitone level in serum was within the effective antico nvulsant concentration range. Phenobarbitone decreased NE levels in HI (P < 0.01), HY (P < 0.05) and CB (P < 0.05), with no alterations in M C, SA and BS regions. On the contrary, DA levels were increased in MC (P < 0.001), SA (P < 0.05) and HY (P < 0.05) but decreased in BS (P < 0.001). Serotonin levels were decreased in MC (P < 0.05), HY (P < 0.01 ) and BS (P < 0.001), while in SA, HI and CB, 5-HT levels did not diff er from control rats. It appears that a given category of nerve termin als might not be identically susceptible to phenobarbitone in differen t regions of the brain. Phenobarbitone seems to exert its anticonvulsa nt action by differentially altering monoamine levels in various brain regions.