The effect of a standardised 50% ethanolic extract of Indian Hypericum perforatum (IHp) was investigated for its putative
nootropic activity on various experimental paradigms of learning and memory, viz. transfer latency (TL) on elevated plus-maze, passive avoidance (PA), active avoidance (AA),
scopolamine and
sodium nitrite induced
amnesia (SIA & NIA) in albino rats. Pilot studies indicated that single dose administration of IHp had little or no acute behavioural effects, hence the extract of IHp was administered orally at two dose levels (100 and 200 mg/kg, p.o.), once in daily for three consecutive days, while
piracetam (500/kg, i.p.), a clinically used
nootropic agent, was administered acutely to rats as the standard
drug. Control rats were treated with equal volume of vehicle (0.3%
carboxymethyl cellulose (CMC)). IHp and
piracetam when given alone shortened the TL on day 1, 2, 9 and also antagonised the amnesic effects of
scopolamine and
sodium nitrite on the TL significantly. IHp had no significant per se effect on the retention of the PA in rats. Only the higher dose (200 mg/kg, p.o.) produced a significant reversal of
scopolamine induced PA retention deficit but no significant reversal was observed with
sodium nitrite.
Piracetam showed significant per se facilitatory effect on PA retention and also reversed the
scopolamine and
sodium nitrite induced impaired PA retention. In the AA test, IHp in both the doses, and
piracetam, facilitated the acquisition and retention of AA in rats and the IHp effects were found to be dose dependent. Both the doses of IHp and
piracetam significantly attenuated the
scopolamine and
sodium nitrite induced impaired retention of AA. These results indicate a possible
nootropic action of IHp, which was qualitatively comparable with that induced by
piracetam.