Honokiol and magnolol increased hippocampal acetylcholine release in freely-moving rats

Honokiol and magnolol, phenolic compounds isolated from the stem bark of Ma gnolia officinalis, have been demonstrated to increase choline acetyltransf erase activity, inhibit acetylcholinesterase, promote potassium-induced ace tylcholine release and exhibit neurotrophic function in in vitro studies. T he objective of the present study was to determine the effect of these comp ounds on hippocampal acetylcholine release in conscious? freely-moving rats . 10(-4) M-10(-6) M of honokiol or magnolol was perfused into rat hippocamp us via a dialysis probe. The results showed that at 10(-4) M concentration, honokiol and magnolol markedly increased extracellular acetylcholine relea se to 165.5 +/- 5.78% and 237.83 +/- 9.47% of the basal level, respectively . However, lower concentrations of either compounds failed to elicit signif icant acetylcholine release. This result suggests that a high dose of honok iol or magnolol may enhance in vivo hippocampal acetylcholine release.