A subpopulation of dopamine D1 receptors mediate repetitive jaw movements in rats

Repetitive jaw movements (RJM) in rats, a potentially useful animal model of tardive dyskinesia, appears to be mediated by the dopamine D1 receptor as evidenced in part by their induction and inhibition with D1 agonists and D1 antagonists, respectively. Selective destruction of 60-90% of D1 receptors by EEDQ, measured in several CNS dopaminergically innervated areas, preceded by protection of D2, 5-HT2, alpha 1 and alpha 2 receptors, however, failed to reduce D1 agonist-augmentable RJM. Further, the affinity of dopamine toward displacement of 3H-SCH-23390 binding from striatal D1 receptors was significantly decreased by administered EEDQ, a counter-intuitive result in relation to D1 responsitivity and RJM. Thus, at present it is suggested that an EEDQ-resistant D1 receptor subpopulation may exist.