TABLE 1

Pharmacological properties of a series of 5-HT₄R ligands on WT 5HT₄R, T3.36A, and W6.48A mutant receptors

Binding assays were performed by using [³H]GR 113808 as the specific 5-HT₄R radioligand in COS-7 cell membranes expressing either WT 5-HT₄R, 5-HT₄-T3.36A, or 5-HT₄-W6.48A. Nonspecific binding was determined with BIMU8 (10 μM). K_D values were determined from Cheng-Prusoff equation (Cheng and Prusoff, 1973). The agonist activity or potency (EC₅₀) was accessed as the concentration that gave 50% increase in the response to cAMP formation. The maximal activity of each drug (E_max) is expressed as a percentage of the maximum 5-HT response obtained with the WT at similar receptor density. All of the data are expressed as means ± S.E.M. of at least four separate experiments.