Fig. 6.
M2 muscarinic receptor-mediated stimulation of phosphoinositide hydrolysis in HEK 293 cells expressing Gα15. a, the effects of muscarinic agonists on [3H]inositolphosphate accumulation are shown. The [3H]inositolphosphate level measured in cells not transfected with the M2 receptor was subtracted from the measurements made in cells transfected with the M2 receptor and normalized relative to the Emax of oxotremorine-M. The data are from Griffin et al. (2007) and represent the mean ± S.E.M. of four to six experiments, each done in triplicate. b, analysis of the data in a yielded estimates of the affinity constants of the agonists for the active (Kb) and inactive (Ka) states of the receptor. The Ka value was assumed to be approximately equal to Kobs.