Effects of honokiol and magnolol on acetylcholine release from rat hippocampal slices.

To study the possible mechanism through which honokiol and magnolol elicit their central depressant effects, we examined the influence of these two phenolic compounds on 25 mM K(+)-stimulated release of [3H]acetylcholine (ACh) from the rat's hippocampal slices. Honokiol, but not magnolol, elicited a concentration-dependent enhancement of K+-evoked ACh release. Addition of either tetrodotoxin, pilocarpine, or methoctramine had no effect on honokiol-enhanced ACh release. These results suggest that honokiol enhanced K(+)-evoked ACh release directly on hippocampal cholinergic terminals via receptors other than the M2 cholinergic subtypes.