The dopamine D3-receptor: A postsynaptic receptor inhibitory on rat locomotor activity

Abstract
We report on the pharmacological effects of the 20 fold D 3 vs. D 2 dopamine receptor preferring compound U 99194 A. It is shown that U 99194 A increases rat locomotor activity at doses that do not increase release or utilisation of dopamine in the striatum or the nucleus accumbens significantly. The data do not support any direct agonist action of U 99194 A at dopamine receptors. It is suggested that U 99194 A can antagonise a population of postsynaptic dopamine receptors involved in the suppression of some aspects of psychomotor activity. These postsynaptic receptors presumably belong to the D 3 receptor subtype.