The effect of subchronic (14 days) administration of a standardized extract of Bacopa monniera (bacoside A content 82%) was evaluated on two animal models of Alzheimer's disease induced by intracerebroventricular administration of colchicines and by lesioning of the nucleus basalis magnocellularis (nbm) with ibotenic acid.
Alzheimer's disease is believed to be associated with impaired cholinergic functions. It is indicated by depleted concentrations of the neurotransmitter, acetylcholine, a reduction in choline esterase activity and decreased muscarinic cholinergic receptor binding in the frontal cortex and hippocampus in rats. Colchicine administration triggered these effects. Lesioning with colchicines or ibotenic acid induced marked deficits in the retention of active avoidance learning on day 7 and increased progressively by day 14.
Subchronic administration of Bacopa monniera at a dose of 10mg/kg significantly reduced the magnitude of memory deficits induced by both compounds as observed on days 7 and 14, while the effects were evident with the lower dose only on day 14 . The dose of 10 mg/kg reversed the detrimental effects induced by the colchicines in the frontal cortex and the hippocampus. The effects of the lower dose of 5 mg/kg were evident only after 14 days of administration. The authors concluded that the memory-facilitating effects of Bacopa monniera and its active constituents , the bacosides, may be due to their effects on central cholinergic modulation of memory functions.