Effect of Ginkgolic acid conjugates on the brain monoamines and metabolites in rodents

Abstract

The effect of acute administration of Ginkgo biloba leaf extract of Indian origin (lGb) 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 different regions of the rodent brain namely, hypothalamus, hippocampus, striatum, ponsmedulla and frontal cortex. lGb extract in the doses 50 and 100 mg/kg., p.o (equivalent to 0.3 and 0.6 mg/kg ginkgolic acid conjugates) significantly decreased the levels of serotonin (5HT) and its metabolite 5-hydroxyindole acetic acid (5HIAA) in all the regions of the brain assayed except the pons medulla. The treatments also augmented the levels of norepinephrine (NE) and its metabolite methylhydroxyphenyl glycol (MHPG), dose dependently in various regions of the brain. Concomitantly, the levels of dopamine (DA) and its metabolite dihydroxyphenyl acetic acid (DOPAC) were augmented significantly in the striatum. However, the turnover rate of the monoamines was not influenced by the drug treatment except that of 5HIAA/5HT in frontal cortex. The neurochemical effects of the ginkgolic acid conjugates can explain some of the behavioural actions induced by them, namely, anxiolytic, antidepressant and cognition facilitatory effects.