Selective Blockade of Dopamine D3 Receptors Enhances while D2 Receptor Antagonism Impairs Social Novelty Discrimination and Novel Object Recognition in Rats: A Key Role for the Prefrontal Cortex

Dopamine D3 receptor antagonists exert pro-cognitive effects in both rodents and primates. Accordingly, this study compared the roles of dopamine D3vs D2 receptors in social novelty discrimination (SND), which relies on olfactory cues, and novel object recognition (NOR), a visual-recognition task. The dopamine D3 receptor antagonist, S33084 (0.04–0.63 mg/kg), caused a dose-related reversal of delay-dependent impairment in both SND and NOR procedures in adult rats. Furthermore, mice genetically deficient in dopamine D3 receptors displayed enhanced discrimination in the SND task compared with wild-type controls. In contrast, acute treatment with the preferential dopamine D2 receptor antagonist, L741,626 (0.16–5.0 mg/kg), or with the dopamine D3 agonist, PD128,907 (0.63–40 μg/kg), caused a dose-related impairment in performance in rats in both tasks after a short inter-trial delay. Bilateral microinjection of S33084 (2.5 μg/side) into the prefrontal cortex (PFC) of rats increased SND and caused a dose-related (0.63–2.5 μg/side) improvement in NOR, while intra-striatal injection (2.5 μg/side) had no effect on either. In contrast, bilateral microinjection of L741,626 into the PFC (but not striatum) caused a dose-related (0.63–2.5 μg/side) impairment of NOR. These observations suggest that blockade of dopamine D3 receptors enhances both SND and NOR, whereas D3 receptor activation or antagonism of dopamine D2 receptor impairs cognition in these paradigms. Furthermore, these actions are mediated, at least partly, by the PFC. These data have important implications for exploitation of dopaminergic mechanisms in the treatment of schizophrenia and other CNS disorders, and support the potential therapeutic utility of dopamine D3 receptor antagonism.