A, phospho-p38 MAPK (P-p38) concentration-response curves for the KOR agonists U50,488 and the endogenous KOR agonist-peptide dynorphin B in AtT-20 cells expressing KOR-GFP. B, phospho-p38 concentration-response curves for the KOR agonists U50,488 and salvinorin A in primary striatal astrocytes. All agonist treatments were performed at the 15-min time point. n = 3– 4, with each n taken from a separate cell culture and experiment.