Dopamine D-1/D-5 receptor activation is required for long-term potentiation in the rat neostriatum in vitro

Dopamine and glutamate are key neurotransmitters involved in learning and memory mechanisms of the brain. These two neurotransmitter systems converge on nerve cells in the neostriatum. Dopamine modulation of activity-dependent plasticity at glutamatergic corticostriatal synapses has been proposed as a cellular mechanism for learning in the neostriatum. The present research investigated the role of specific subtypes of dopamine receptors in long-term potentiation (LTP) in the corticostriatal pathway, using intracellular recording from striatal neurons in a corticostriatal slice preparation. In agreement with previous reports, LTP could be induced reliably under Mg2+-free conditions. This Mg2+-free LTP was blocked by dopamine depletion and by the dopamine D-1/D-5 receptor antagonist SCH 23390 but was not blocked by the dopamine D-2 receptor antagonist remoxipride or the GABA(A) antagonist picrotoxin. In dopamine-depleted slices, the ability to induce LTP could be restored by bath application of the dopamine D-1/D-5 receptor agonist, SKF 38393. These results show that activation of dopamine D-1/D-5 receptors by either endogenous dopamine or exogenous dopamine agonists is a requirement for the induction of LTP in the corticostriatal pathway. These findings have significance for current understanding of learning and memory mechanisms of the neostriatum and for theoretical understanding of the mechanism of action of drugs used in the treatment of psychotic illnesses and Parkinson's disease.