Disruption of orofacial movement topographies in congenic mutants with dopamine D5 but not D4 receptor or DARPP-32 transduction ‘knockout’

The role of D1-like [D1, D5] and D2-like [D2, D3, D4] dopamine receptors and dopamine transduction via DARPP-32 in topographies of orofacial movement was assessed in restrained mice with congenic D4 vs. D5 receptor vs. DARPP-32 ‘knockout’. D4 and DARPP-32 mutants evidenced no material phenotype; also, there were no alterations in topographical responsivity to either the selective D2-like agonist RU 24213 or the selective D1-like agonist SK and F 83959. In contrast, D5 mutants evidenced an increase in spontaneous vertical jaw movements, which habituated more slowly than in wildtypes, and a decrease in horizontal jaw movements; topographical responsivity to SK and F 83959 and RU 24213 was unaltered. D5 receptors regulate distinct topographies of vertical and horizontal jaw movement in an opposite manner. In assuming that the well-recognised role of the D1-like family in regulating orofacial movements involves primarily D1 receptors, a role for their D5 counterparts may have been overlooked.