Hypericum extract and hyperforin: Memory-enhancing properties in rodents

Effects of a Hypericum extract in therapeutic use and hyperforin sodium sal t were evaluated in rat and mouse avoidance tests. In a conditioned avoidan ce response (CAR) test on the rat, oral daily administration of hyperforin (1.25 mg/kg/day) or of the extract (50 mg/kg/day) before the training sessi ons considerably improved learning ability from the second day onwards unti l the day 7. In addition, the memory of the learned responses acquired duri ng 7 consecutive days of administration and training was largely retained e ven after 9 days without further treatment or training. The observations ma de using different doses indicate that these learning-facilitating and/or m emory-consolidating effects by the agents follow inverse U-shaped dose-resp onse curves in dose ranges lower than (for hyperforin) or equal to (for Hyp ericum extract) their effective dose in the behavioral despair test for ant idepressants. In a passive avoidance response test on the mouse, a single o ral dose (1.25 mg/kg) of hyperforin not only improved memory acquisition an d consolidation, but also almost completely reversed scopolamine-induced am nesia. The single Hypericum extract dose tested (25 mg/kg) did not reveal a ny significant effects in the passive avoidance response (PAR) test on the mouse. These observations suggest that the Hypericum extract could be a nov el type of antidepressant with memory enhancing properties, and indicate th at hyperforin is involved in its cognitive effects. Pure hyperforin seems t o be a more potent antidementia agent than an antidepressant.