Link between dopamine D1 and D2 receptors in rat and human striatal tissues

Abstract
Many psychomotor behaviors depend on an interaction between dopamine D1 and D2 receptors. This study tested the hypothesis that agonist stimulation of dopamine D1 receptors leads to the conversion of D2 receptors from a state of high affinity for dopamine into a state of low affinity for dopamine. To test this hypothesis, dopamine was competed against [3H]raclopride for binding to rat and human striatal homogenates. Although the detection of high-affinity states of the dopamine D2 receptor in rat or postmortem human striatum is normally difficult because the proportions of such sites are very low in the presence of physiological concentrations of sodium ions, the present work found that in the presence of 100 nM SCH 23390 to block D1 receptors, a significant proportion of D2 high-affinity sites were unmasked and readily revealed to be 10–35% of the D2 population, illustrating the presence of a strong D1–D2 link in both rat and human striata. Synapse 47:250–254, 2003.

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