Selective protection from the inhibition by EEDQ of D1 and D2 dopamine agonist-induced rotational behavior in mice.

Mice with unilateral lesions of dopamine nigrostriatal neurons produced by injecting 6-hydroxydopamine into the striatum exhibited contralateral rotational behavior to the non-selective dopamine agonist apomorphine, the D1 dopamine agonist SKF 38393, and the D2 agonist quinpirole. The non-specific dopamine antagonist EEDQ blocked the circling responses to the three agonists. Pretreatment with specific, reversible dopamine antagonists before the EEDQ injection selectively prevented this blockade. Thus, if mice were pretreated with the D1 receptor antagonist SCH 23390 before EEDQ and the animals challenged with the D1 and D2 agonists 24 hours later, the rotational response to quinpirole was still inhibited, but the response to SKF 38393 was now evident. Similarly, in mice pretreated with the D2 receptor antagonist sulpiride before EEDQ and again challenged with the D1 and D2 agonists 24 hours later, the rotational response to SKF 38393 was still inhibited but the response to quinpirole was no longer inhibited. These results indicate that in vivo blockade of either D1 or D2 subpopulations of dopamine receptors may be achieved by selective protection with a reversible dopamine antagonist given prior to the administration of an irreversibly acting dopamine antagonist such as EEDQ.