Stereoselective Interaction of Mianserin with 5-HT3 Receptors

Abstract
The interaction of the enantiomers of mianserin with the 5-HT3 receptor was determined. Using [3H]granisetron binding, (–)-mianserin was more potent than (+)-mianserin (pKi 8·46 and 6·95, respectively). The enantiomers competitively antagonized the depolarizing effect of 5-hydroxytryptamine in the rat vagus nerve preparation (pKapp: (–)-mianserin 8·13, (+)-mianserin 6·58). This stereoselectivity was maintained in-vivo as determined using ex-vivo inhibition of [3H]granisetron binding. Therefore, in contrast to its enantiomeric selectivity for the 5-HT1C and 5-HT2 receptors, where the (+)-isomer is more potent, the enantiomeric selectivity of mianserin for the 5-HT3 receptor was reversed. This differential selectivity of the enantiomers of mianserin may be useful in elucidating its utility in anxiety states.

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