TABLE 1

Competition binding values of WIN55,212-2, FTY720, sphingosine, and S1P for [³H]cannabinoid ligand binding to CB₁ receptors

Membranes prepared from the indicated tissue were incubated with [³H]SR141716A or [³H]CP55,940 in the presence and absence of varying concentrations of WIN55,212-2, FTY720, sphingosine, or S1P. The competition binding data were fitted to the Hill equation to determine IC₅₀ and n_H values. The resulting IC₅₀ values were converted to pK_i values as described under Data Analysis. Values shown are mean ± S.E. of three to four experiments performed in triplicate. Pairs of pK_i values with different letter designations (a, b, c) within a particular cell type-radioligand competition group are p < 0.05 different from each other by Tukey-Kramer test, whereas those with the same letter designations are not significantly different.