Long-term potentiation (LTP) is thought as a generative mechanism underlying learning and memory via storing information in central nervous system. Electro-neurophysiological assay for LTP is generally used in screening the drugs that can facilitate learning and memory. By using in vivo LTP technique, isolichenin was found to facilitate LTP induction by a tetanic stimulation (20 pulses/100 Hz) in dentate gyrus. This tetanic stimulation by itself, however, cannot induce LTP. Previous study showed the reagent being able to facilitate LTP-induction, like methanol extract of saffron (MES), usually can antagonize the inhibiting effect of 30% ethanol on LTP induction (30 pulses/60 Hz). Isolichenin may also fall into such kind of drugs. Interestingly, comparatively study showed that isolichenin failed to antagonize the inhibiting effect of 30% ethanol on LTP induction (30 pulses/60 Hz). This result indicates a different unknown mechanism existing in the effect of isolichenin on LTP or memory formation.