Selective antagonism at dopamine D3 receptors enhances monoaminergic and cholinergic neurotransmission in the rat anterior cingulate cortex

Recent neuroanatomical and functional investigations focusing on dopamine (DA) D-3 receptors have suggested a potential role of this receptor in psychiatric diseases such as schizophrenia and drug dependence. In line with the key role of the prefrontal cortex in psychiatric disorders, the present study aimed at assessing the effects of the acute systemic administration of the selective DA D-3 receptor antagonist SB-27701 1-A on the in vivo extracellular levels of monoamines (DA norepinelphrine (NE), and serotonin (5-HT)) and acetylcholine (ACh) in the anterior cingulate subregion of the medial prefrontal cortex. The in vivo neurochemical profile of SB-27701 1-A (10 mg/kg, i.p.) in the anterior cingulate cortex was compared with both typical and atypical antipsychotics including dozapine (10 mg/kg, s.c.), olanzapine (10 mg/kg, s.c.), sulpiride (10 mg/kg, s.c.), and haloperidol (0.5 mg/kg, s.c.). The acute administration of SB-27701 1-A, clozapine, and olanzapine produced a significant increase in extracellular levels of DA, NE, and ACh without affecting levels of 5-HT. Sulpiride also significantly increased extracellular DA, but with a delayed onset over SB-27701 1-A, clozapine, and olanzapine. In contrast, haloperidol failed to alter any of the three monoamines and ACh in the anterior cingulate cortex. These findings add to a growing body of evidence suggesting a differentiation between typical and atypical antipsychotic drugs (APDs) in the anterior cingulate cortex and a role of DA D-3 receptors in desired antipsychotic drug profile. Similar to their effects on DA and NE, SB-27701 1-A, clozapine, and olanzapine increased extracellular levels of ACh, whereas haloperidol and sulpiride did not alter ACh. The results obtained in the present study provide evidence of the important role of DA D-3 receptors in the effect of pharmacotherapeutic agents that are used for the treatment of psychiatric disorders such as schizophrenia and drug dependence.