Shinobu Akuzawa, Hiroyuki Ito and Tokio Yamaguchi
Neuroscience Research, Pharmacology Laboratories, Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., 2I Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
Abstract: Characteristics of the binding of [3H]ramosetron to cloned human 5-hydroxytryptamine3 (5-HT3) receptors were investigated and directly compared to those of [3H]granisetron binding. Saturation studies revealed that [3H]ramosetron labeled more sites with high affinity (Kd=0.15+/-0.01 nM, Bmax=653+/-30 fmol/mg protein) than [3H]granisetron (Kd=1.17+/-0.25 nM, Bmax=427+/-43 fmol/mg protein). Kinetic studies revealed that dissociation of [3H]ramosetron was slower than that of [3H]granisetron. These results suggest that ramosetron is a highly potent 5-HT3-receptor antagonist.
Keywords: Ramosetron, Granisetron, 5-HT3 receptor