Decreased c-fos responses to dopamine D-1 receptor agonist stimulation in mice deficient for D-3 receptors

The acute administration of dopamine D-1 receptor agonists induces the expr ession of the immediate early gene c-fos. In wild type mice, this induction is completely abolished by pretreatment with the D-1-selective antagonist SCH23390, and pretreatment with the D-2-like receptor antagonist eticloprid e reduces the levels of c-fos expressed in response to D-1 receptor stimula tion. Mice deficient for the dopamine D-3 receptor express levels of D-1 ag onist-stimulated c-fos immunoreactivity that are lower than c-fos levels of their wild type littermates. Moreover, the acute blockade of D-2 receptors in D-3 mutant mice further reduces c-fos expression levels. These data ind icate that the basal activity of both D-2 and D-3 receptors contributes to D-1 agonist-stimulated c-fos responses. The findings therefore indicate tha t not only D-2 but also D-3 receptors play a role in dopamine-regulated gen e expression.