Glutamate receptors in the dopamine system – function and role in reinforcement learning

Midbrain dopamine neurons along with the major target of their projections, dopaminoceptive neurons in striatum, regulate reinforcement learning and motivation. The activity and plasticity in the dopamine system are largely dependent on excitatory glutamatergic transmission. The article describes the functional role of N-methyl-D-aspartate (NMDA) receptors in driving the phasic activity in dopamine neurons, and a role of NMDA and metabotropic glutamate 5 (mGluR5) receptors in induction of plasticity in dopaminoceptive striatal medium spiny neurons. Based on published studies on genetically modified mice, the article further discusses how targeted loss of glutamate receptor-dependent signalling in dopamine system affects reinforcement learning and motivational processes. The conclusion of the article is the view that aberrant glutamate signalling in dopamine system may contribute to maladaptive behaviours, which are particularly often observed in mental disorders.