Transient hypersensitivity to apomorphine-induced gnawing after termination of acute effects high dose of cocaine

Male mice were tested for behavioral effects (BEs) of the dopamine (DA) agonist apomorphine (AP) at various times after acute administration of cocaine (COC). When most of the COC had disappeared from brain and the BEs of COC had dissipated (2 hrs and 4 hrs after administration), effects of AP on gnawing were increased 4-fold. This dopaminergic hypersensitivity (DA-H) was induced by acute treatment with doses of 15 mg/kg COC and higher. Effects of AP were not enhanced 6-24 hrs after COC, indicating a rapid waning of the DA-H. Hypersensitivity to AP (AP-H) was not further augmented by 8 days of daily COC injections. COC did not influence climbing and hypomotility induced by AP 4 hrs after its injection, demonstrating selectivity in the BEs of the DA-H. Further, COC did not induce sensitization to its own effects, indicating that the AP-H was not due to a typical sensitization phenomenon. ((c) 1997 APA/PsycINFO, all rights reserved)