Participation of the serotonergic system in the memory effects of Ginkgo biloba L. and Panax ginseng C. A. Mey

The 7-day oral administration of the extracts from Ginkgo biloba (GK501) and Panax ginseng (G115) as well as their combination PHL-00701 (Gincosan®) produced changes in rat behaviour suggesting memory-enhancing effects. Single doses of agonists and antagonists of different serotonin receptor subtypes influenced the rat's capability for retention of learned behaviour and the behavioural effects of the drugs tested. GK501 decreased the density (B_max) of 5-HT₁ receptors in the frontal cerebral cortex and hippocampus. Data concerning the effects of the drugs tested suggest the participation of the serotonergic transmitter system as an important neurochemical correlate of rat behaviour and of the memory effects of the drugs studied. This participation is modulated by the differences in the functions of the serotonin receptor subtypes.