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Receptor binding profile of Otilonium bromide
S Evangelista1, A Giachetti, B Chapelain
1Menarini Ricerche S.P.A., Firenze, Italy.
Pharmacological Research
|August 29, 1998
Summary
Otilonium bromide (OB) acts as an antispasmodic by blocking muscarinic receptors and L-type calcium channels. This dual action provides a molecular basis for its effectiveness in relieving intestinal smooth muscle spasms.
Area of Science:
- Pharmacology
- Gastroenterology
- Molecular Biology
Background:
- Otilonium bromide (OB) is a known antispasmodic agent used for treating gastrointestinal disorders.
- Its precise molecular mechanisms of action, particularly its interactions with various receptors and ion channels, require detailed investigation.
Purpose of the Study:
- To investigate the interaction of Otilonium bromide (OB) with a wide range of receptor and ion channel binding sites.
- To elucidate the molecular targets responsible for OB's spasmolytic effects in intestinal smooth muscle.
Main Methods:
- Binding assays were performed to assess OB's affinity for 63 different receptors and ion channels.
- In vivo experiments were conducted using rat colon tissue to evaluate OB's interactions with specific targets.
- Inhibition constants (IC50) were determined for competitive interactions with verapamil binding sites on L-type Ca2+ channels and muscarinic M2 receptors.
Main Results:
- OB demonstrated sub-micromolar affinity for muscarinic M1, M2, M4, M5, and PAF receptors.
- OB exhibited micromolar affinity for the diltiazem binding site on L-type Ca2+ channels.
- In rat colon, OB competitively interacted with L-type Ca2+ channels (verapamil site) and muscarinic M2 receptors, with IC50 values of 1020 nM and 1220 nM, respectively.
Conclusions:
- The findings suggest a dual mechanism of action for OB, involving both antimuscarinic and calcium channel blocking properties.
- This combined pharmacological profile provides a molecular explanation for OB's spasmolytic activity on intestinal smooth muscle.