RECEPTOR-BINDING PROFILE OF OTILONIUM BROMIDE

The interaction of Otilonium bromide (OB) with binding sites for 63 di fferent receptors and ion channels in appropriate preparations has bee n investigated. Experiments were also performed in rat colon, the pref erred tissue for OB 'in vivo' uptake after oral administration. Among the receptors investigated OB binds with sub mu M affinity to muscarin ic M-1, M-2, M-4, M-5 and PAF receptors and with mu M affinity to the diltiazem binding site on L type Ca2+ channels. In the rat colon OB sh ows competitive interaction with the verapamil binding site on L type Ca2+ channels and with muscarinic M-2 receptors with IC50 of 1020 and 1220 nM, respectively. These findings provide a molecular rationale to explain the spasmolytic action exerted by OB on intestinal smooth mus cle. In particular, a combination of antimuscarinic and Ca2+ channel b locker properties seems to best account for the action of this compoun d. (C) 1998 The Italian Pharmacological Society.