The effects of PDE10 inhibition on attentional set-shifting do not depend on the activation of dopamine D1 receptors.

Abstract

Inhibitors of phosphodiesterase 10A (PDE10A) represent a novel class of potential antipsychotic compounds. These principles increase the level of cAMP and cGMP in the medium spiny neurons of the striatum and resemble the neurochemical consequences of dopamine D2 receptor inhibition and dopamine D1 receptor stimulation. Cognitive dysfunctions, including an impaired ability to shift perceptual attentional set, are core features of schizophrenia. In the present study, we investigated the involvement of D1 receptors in the procognitive action of the PDE10A inhibitor using the attentional set-shifting task in rats. The performance of the rats in the extradimensional shift stage of the attentional set-shifting task was taken as an index of cognitive flexibility. We first assessed the effects of the D1 agonist in otherwise untreated animals and in animals pretreated with the D1 receptor antagonist. We then investigated the procognitive effects of the PDE10A inhibitor, MP-10, in otherwise untreated animals and in animals pretreated with the D1 receptor antagonist. The dopamine D1 receptor antagonist SCH-23390 produced cognitive impairment at the dose of 0.0125 mg/kg, but not at 0.0063 mg/kg. The D1 receptor agonist, SKF-81,297, produced a procognitive effect that was abolished by 0.0063 mg/kg of SCH-23390. The compound MP-10 produced a procognitive effect at the dose of 0.3 mg/kg, but not at 0.1 mg/kg. Rat pretreatment with 0.0063 mg/kg of SCH-23390 did not block the procognitive effect of 0.3 mg/kg of MP-10. The present study demonstrates that the blockade of dopamine D1 receptors is unlikely to affect the procognitive effects of PDE10A inhibition.