D2-like receptors in nucleus accumbens negatively modulate acetylcholine release in prefrontal cortex

Glutamatergic and dopaminergic inputs converge on medium spiny neurons in nucleus accumbens and regulate the excitability of these projections to target areas including the cholinergic basal forebrain. NMDA receptors situated on these projections are locally modulated by D1- and D2-like receptors. We previously reported that the D1-like positive modulation of NMDA receptor activity is expressed trans-synaptically in the control of basal forebrain cholinergic projections to prefrontal cortex. The present experiments tested the hypothesis that D2-like receptors in accumbens negatively modulate cortical ACh release. Perfusion of NMDA (150 microM) into the shell region of the accumbens produced a sustained increase (150-200%) in ACh release in prefrontal cortex. This increase was completely blocked by co-perfusion with the D2-like agonist quinpirole (100 microM). Perfusion of quinpirole also reduced basal ACh release (approximately 50%) in prefrontal cortex. The contribution of D2 receptors to the quinpirole effect was assessed in two additional studies. The first study revealed that co-perfusion of the D2 antagonist haloperidol (100 microM) blocked the quinpirole-induced attenuation of NMDA mediated ACh release. The second experiment demonstrated that intra-accumbens perfusion of quinelorane (100 microM), a more selective D2 agonist than quinpirole, also attenuated the NMDA mediated ACh release. Collectively, these studies demonstrate that D2 receptors in accumbens negatively modulate basal and NMDA mediated increases in ACh release in prefrontal cortex. This negative modulation may contribute to the integration of normal attentional processing and goal directed behavior and to the therapeutic effects of antipsychotic medication on cognition in psychopathologies such as schizophrenia.