Fig 4. Nuciferine functional activity at the dopamine D₂ receptor as measured via D₂-mediated G_i signaling in HEKT cells.

(a) Concentration-response curve of nuciferine (red) compared to dopamine (black) and aripiprazole (blue). (b) Concentration-response curve of dopamine (DA) in the presence of 1 μM nuciferine (red) or clozapine (green) showing rightward-shift of DA indicative of competitive antagonist activity. The data represent concentration-response curves of normalized data with respect to dopamine performed in triplicate (mean +/- s.e.m.; n = 3).