Dose-dependent responses of agonists in distinct cell lines. (a, b) Dose responses of DPDPE in HEK-DOR; (c, d) Dose responses of BRL-52537 in HEK-KOR; and (e, f) Dose responses of DAMGO in SH-SY5Y cells. (a, c, e) Real time DMR, each curve represents the mean ± s.d. of 2 independent measurements, each in duplicate (n = 4). (b, d, f) The maximal amplitudes as a function of agonist doses (n = 4).