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. Author manuscript; available in PMC: 2018 May 9.
Published in final edited form as: J Am Chem Soc. 2017 Dec 13;139(51):18522–18535. doi: 10.1021/jacs.7b07659

Figure 4.

Figure 4

MAP is a neutral antagonist at D1R(I183C). (A) Ribbon representation of a D1R homology model bound to protonated DA (red). Amino acid I183 in EL2 is shown in green above the OBS that binds DA. (B) When MAP is attached to I183C, photoswitching between 360 nm (gray bars) and 460 nm light (blue bars) had no effect. However, current evoked by DA was photoblocked in response to 460 nm light. (C) Representative trace of currents induced by DA under 360 nm light (gray) or 460 nm light (blue). Ramp currents were subtracted from baseline ramps taken in the absence of DA under 360 nm light. Currents show inward rectification typical of GIRK current. Inset shows close overlap between the normalized traces. (D) The kinetics of the onset and offset of photoblock at D1R(I183C) by MAP were not significantly different (n.s. = not significant, two-tailed, unpaired t test). Error bars represent SEM. (E) Photoblock of D1R(I183C) by MAP is bistable. A brief flash of 460 nm light (blue bar) induced a decrease in dopamine-evoked current that was sustained in the dark for ~30 s until it was reversed by a brief flash of 360 nm light (gray bar). (F) The magnitude of photoblock of D1R(I183C) by MAP decreases with increasing concentrations of DA. Error bars represent SEM for n = 3–9 cells per concentration of DA.