Phosphodiesterase 10A inhibition modulates the sensitivity of the mesolimbic dopaminergic system to d-amphetamine: involvement of the D₁-regulated feedback control of midbrain dopamine neurons

Phosphodiesterase (PDE) 10A is highly expressed in medium spiny neurons of the striatum, at the confluence of the corticostriatal glutamatergic and the midbrain dopaminergic pathways, both believed to be involved in the physiopathology of schizophrenia. There is a growing body of evidence suggesting that targeting PDE10A may be beneficial for the treatment of positive symptoms in schizophrenia. The aim of the present study was to investigate how PDE10A inhibition modulates mesolimbic dopaminergic neurotransmission. We found that the selective PDE10A inhibitor, MP-10, blocked d-amphetamine-induced hyperactivity as well as d-amphetamine-induced dopamine efflux in the nucleus accumbens in a dose-dependent manner. We further investigated the mechanism by which PDE10A inhibition affects dopaminergic neurotransmission. We report that MP-10 potentiated the effect of a high but not a low dose of d-amphetamine on the mean firing rate of dopaminergic neurons recorded from the ventral tegmental area. Similarly, the effect of a high, but not a low dose of d-amphetamine, was completely reversed by the selective D₁ antagonist, SCH23390. These data suggest that the D₁-regulated feedback control of midbrain dopamine neurons is a critical pathway involved in the modulation of the response of mesolimbic dopamine neurons to d-amphetamine by PDE10A inhibition.