Molecular effects of dopamine on striatal-projection pathways.

Gene regulation studies demonstrate that dopamine differentially regulates the direct and indirect projection neurons of the striatum through their respective expression of the D1 and D2 dopamine receptors. Induction of immediate-early genes (IEGs) in striatal neurons is used to study dopamine-receptor-mediated neuronal plasticity. In the dopamine-depleted striatum there is a switch in receptor-mediated signal transduction mechanisms to produce a supersensitive form of D1- mediated neuronal plasticity. This switch is suggested to underlie dopamine-agonist-induced dyskinetic movements that develop during the treatment of Parkinson's disease.