Topographical effects of D 1 -like dopamine receptor agonists on orofacial movements in mice and their differential regulation via oppositional versus synergistic D 1 -like: D 2 -like interactions: cautionary observations on SK&F 82958 as an anomalous agent

Abstract

Using a novel procedure, the regulation of individual topographies of orofacial movement in the mouse by oppositional versus cooperative/synergistic D₁-like: D₂-like dopamine receptor interactions was studied. The D₁-like agonists SK&F 38393 and SK&F 83959 each induced vertical, but not horizontal, jaw movements, together with tongue protrusions and incisor chattering; however, SK&F 82958 induced a different profile which, consistent with other neurochemical and neurophysiological studies, suggests that this agent shows anomalous properties relative to other D₁-like agonists. When given alone, the D₂-like agonist quinpirole reduced horizontal jaw movements and incisor chattering. On coadministration, both SK&F 38393- and SK&F 83959-induced vertical jaw movements and tongue protrusions were inhibited by quinpirole, while SK&F 82958 again showed an anomalous profile. These findings indicate that, in the mouse, vertical jaw movements and tongue protrusions are regulated by oppositional D₁-like: D₂-like interactions, and appear to involve a D₁-like receptor that is not coupled to adenylyl cyclase, whereas horizontal jaw movements are inhibited by D₂-like receptors. Additionally, results obtained using SK&F 82958 as a probe for D₁-like mechanisms should be treated with considerable caution until they are confirmed using other D₁-like agonists.