Dissociation of autoreceptor activation and behavioral consequences of low-dose apomorphine treatment

1. Low dose dopaminergic agonist effects have been used as a behavioral screen for identifying compounds with selective autoreceptor activity. 2. However, results from several recent investigations suggest that these behaviors may not be generated from an autoreceptor substrate but rather from a subpopulation of postsynaptic dopamine receptors with a high affinity for the agonist. 3. In support of this hypothesis, the present investigation reports that both hypomotility and yawning, induced in the rat with 0.07 mg/kg apomorphine, were not paralleled by autoreceptor-induced reductions in transmitter metabolism from either mesolimbic or neostriatal dopamine regions.