Amphetamine selectively blocks inhibitory glutamate transmission in dopamine neurons

Abstract

Amphetamine is a highly addictive psychostimulant that promotes the release of the catecholamines dopamine and norepinephrine. Amphetamine-induced release of dopamine in the midbrain inhibits the activity of dopamine neurons through activation of D-2 dopamine autoreceptors. Here we show that amphetamine may also excite dopamine neurons through modulation of glutamate neurotransmission. Amphetamine potently inhibits metabotropic glutamate receptor (mGluR)-mediated IPSPs in dopamine neurons, but has no effect on ionotropic glutamate receptor-mediated EPSCs. Amphetamine desensitizes the mGluR-mediated hyperpolarization through release of dopamine, activation of postsynaptic alpha (1) adrenergic receptors, and suppression of InsP(3)-induced calcium release from internal stores. By selectively suppressing the inhibitory component of glutamate-mediated transmission, amphetamine may promote burst firing of dopamine neurons. Through this mechanism, amphetamine may enhance phasic release of dopamine, which is important in the neural processing of reward.