Bacopa monniera alleviates Nω-nitro-l-arginine-induced but not MK-801-induced amnesia: A mouse Morris water maze study

N-methyl-d-aspartate (NMDA) receptor and nitric oxide syntheses are the emerging target sites for development of novel drug molecules because their modulation affects the long term potentiation (LTP) process. NMDA receptor antagonists and nitric oxide synthase inhibitors induce amnesia in animals and therefore have been employed for evaluation of efficacy of several novel antiamnesic agents. Bacopa monniera Linn (syn. Brahmi) is commonly used in the ancient Indian medical system for improvement of memory deficit. We have earlier described the involvement of GABAergic and cholinergic system to account for the antiamnesic effects of B. monniera on diazepam- and scopolamine-induced amnesia. In extension to our previous study this study was designed to investigate the downstream mechanism of B. monniera by evaluation of its effect on MK-801 (an NMDA receptor antagonist) and Nω-nitro-l-arginine (l-NNA) (a nitric oxide inhibitor) induced memory deficit. We used a Morris water maze scale and compared the degree of reversal of amnesia induced by the two agents. Male Swiss albino mice were subjected to a Rota-rod muscle incoordination test followed by water maze tasks. Our data revealed that l-NNA and MK-801 produced anterograde and retrograde amnesia and B. monniera significantly attenuated the l-NNA-induced anterograde amnesia, partially reversing l-NNA-induced retrograde amnesia. On the other hand, B. monniera neither attenuated the MK-801-induced anterograde amnesia nor improved retrograde amnesia caused by it.