EFFECT OF GINKGOLIC ACID CONJUGATES ON THE BRAIN MONOAMINES AND METABOLITES IN RODENTS

The effect of acute administration of Ginkgo biloba leaf extract of In dian origin (IGb) mainly constituting ginkgolic acid conjugates (1a-e) . (and their equivalents) have been evaluated on the concentrations of catecholamines, serotonin and their major metabolites in five differe nt regions of the rodent brain namely, hypothalamus, hippocampus, stri atum, ponsmedulla and frontal cortex. IGb extract in the doses 50 and 100 mg/kg., p.o (equivalent to 0.3 and 0.6 mg/kg ginkgolic acid conjug ates) significantly decreased the levels of serotonin (5HT) and its me tabolite 5-hydroxyindole acetic acid (5HIAA) in all the regions of the brain assayed except the pens medulla. The treatments also augmented the levels of norepinephrine (NE) and its metabolite methylhydroxyphen yl glycol (MHPG), dose dependently in various regions of the brain. Co ncomitantly, the levels of dopamine (DA) and its metabolite dihydroxyp henyl acetic acid (DOPAC) were augmented significantly in the striatum . However, the turnover rate of the monoamines was not influenced by t he drug treatment except that of 5HIAA/5HT in frontal cortex. .The neu rochemical effects of the ginkgolic acid conjugates can explain some o f the behavioural actions induced by them, namely, anxiolytic, antidep ressant and cognition facilitatory effects.