D-1 DOPAMINE-RECEPTORS MEDIATE NEUROLEPTIC-INDUCED FOS EXPRESSION IN THE ISLANDS OF CALLEJA

Systemic injections of the selective, full, D-1 agonists A-77636 and S KF-82958 induced pronounced Fos-like immunoreactivity in the islands o f Calleja in the olfactory tubercle of intact rats. Fos expression in this region could also be induced by injections of the D-2-like dopami ne antagonist raclopride (0.5 mg/kg). Pretreatment with the selective D-1 dopamine antagonist SCH-23390 (0.2 mg/kg) completely abolished thi s response, but was without significant effect on raclopride-induced F os expression in the dorsolateral region of the striatum. SCH-23390 wa s also able to prevent the atypical neuroleptic clozapine (30 mg/kg) f rom inducing Fos expression in the islands of Calleja. These findings demonstrate that stimulation of D-1 dopamine receptors plays an essent ial role in neuroleptic induction of Fos-like immunoreactivity in the islands of Calleja, but not in the dorsal striatum, and thus suggest t hat different mechanisms underlie neuroleptic stimulation of immediate early gene expression in these two structures. (C) 1998 Wiley-Liss, I nc.