Jpn. J. Pharmacol. 79 (2), 203-212 (1999)

Identification of SK-951, a Novel Benzofuran Derivative, as an Agonist to S-HT4 Receptors

Motohiro Takeda (1), Katsura Tsukamoto (1), Yuka Mizutani (1), Tsunemasa Suzuki (1) and Kohtaro Taniyama (2)

(1) Pharmaceutical Laboratory, Sanwa Kagaku Kenkyusho Co., Ltd., Shiosaki, 363, Hokusei-cho, Inabe-gun, Mie 511-0406, Japan
(2) Department of Pharmacology, Nagasaki University School of Medicine, Sakamoto 1-12-4, Nagasaki 852-8523, Japan

Abstract: The pharmacological profile of SK-951


methylbenzo[b]furan-7-carboxamide hemifumarate) was identified in relation to serotonin 5-HT3 and 5-HT4 receptors by the receptor binding assay and functional studies. The receptor binding assay showed that SK-951 bound to the 5-HT3 receptor with a high affinity, to the 5-HT4 receptor with relatively higher affinity and to the muscarinic M2 receptor with a low affinity, but not to dopamine D1 and D2 and serotonin 5-HT1 and 5-HT2 and muscarinic M1 and M3 receptors. SK-951 caused relaxations of tunica muscularis mucosae preparations from rat esophagus which were precontracted with carbachol, and the effects were antagonized by GR113808, a selective 5-HT4 antagonist. In the longitudinal muscle with myenteric plexus (LMMP) preparations from guinea pig ileum, SK-951 enhanced the electrically-stimulated contraction of preparations in which the 5-HT1, 5-HT2 and 5-HT3 receptors were blocked, and it enhanced the electrically-stimulated release of [3H]acetylcholine (ACh). These effects of SK-951 were antagonized by GR113808. SK-951 inhibited the 5-HT3 receptor-mediated contractions. These results indicate that SK-951 possesses properties of an agonist for the 5-HT4 receptor and an antagonist for the 5-HT3 receptor. Thus, SK-951 is a new and potent 5-HT4-receptor agonist and causes contractions of guinea pig ileum mediated by enhancement of ACh release via the 5-HT4 receptor.

Keywords: 5-HT4 receptor, Benzofuran derivative, SK-951, Rat esophagus, Guinea pig ileum

Copyrightę The Japanese Pharmacological Society 1999

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