Behavioral sensitization to apomorphine in pigeons (Columba livia): blockade by the D1 dopamine antagonist SCH-23390.

Repeated administration of apomorphine leads to a context-dependent pecking response sensitization. Previously sensitized pigeons (Columba livia) challenged with saline in the same context show a conditioned response (CR). The authors studied the effects of intrastriatal injections of the dopamine (D(1)) antagonist SCH-23390 on both the sensitized response and the CR. When coadministered with apomorphine, SCH-23390 inhibited the initial response to apomorphine, prevented the development of sensitization, and impaired the maintenance of an already developed sensitization. However, SCH-23390 had no effect on the retrieval of a previously established CR. It is concluded that the activation of D(1) receptors in the caudal avian striatum is necessary for the acquisition and maintenance of the sensitization, but not for the expression, of the CR. Copyright 2004 APA.