Abstract
Recent evidence suggests that the trace amine-associated receptor 1 (TAAR1) plays a pivotal role in the regulation of dopamine (DA) transmission and cocaine's actions. However, the underlying mechanisms through which TAAR1 activation mediates these effects have not yet been elucidated. Here, we used fast-scan cyclic voltammetry to measure DA dynamics and explore such mechanisms. We show, first, that the full TAAR1 agonist, RO5256390, dose-dependently blocked cocaine-induced inhibition of DA clearance in slices of the nucleus accumbens. Second, subthreshold inhibition of PKA or PKC phosphorylation did not prevent TAAR1 suppression of cocaine effects whereas subeffective doses of the DA D2 receptor antagonist, L-741,626, rescued cocaine's ability to produce changes in DA uptake in the presence of full TAAR1 activation, thus indicating that TAAR1 modulation of cocaine effects requires simultaneous DA D2 receptor activation. Predictably, inhibition of glycogen synthase kinase-3 (GSK-3), which results from activation of D2/TAAR1 heterodimers, fully reproduced the inhibitory effects of TAAR1 activation on cocaine-induced changes in DA transmission. Collectively, the present observations reveal that the ability of TAAR1 to regulate cocaine effects is linked to cooperative interactions with D2 autoreceptors and associated downstream molecular targets converging on GSK-3 and suggest a new mechanism to disrupt cocaine neurochemical actions.