Rationale: Second-generation antipsychotics have some beneficial effect on cognition. Recent studies, furthermore, indicate differential effects of second-generation antipsychotics on impairment in executive cognitive function.
Objective: We evaluated the effect of the second-generation antipsychotic drug, sertindole, on extracellular levels of dopamine (DA), acetylcholine (ACh), and glutamate (Glu) in the rat medial prefrontal cortex (mPFC). Risperidone was studied for comparison. Moreover, selective serotonin 5-HT(2A), 5-HT(2C), and 5-HT(6) receptor antagonists were used, given alone and in combination with the preferential DA D(2) receptor antagonist, haloperidol, to further clarify the action of the two drugs.
Materials and methods: Rats were treated acutely with vehicle or drugs, and extracellular levels of neurotransmitters were assessed by microdialysis in freely moving animals.
Results: Sertindole and risperidone significantly increased extracellular levels of DA. Haloperidol; the 5-HT(2A) receptor antagonist, M100907; the 5-HT(2C) receptor antagonist, SB242084; and the 5-HT(6) receptor antagonist, GSK-742457, induced minor increases in levels of DA, but the three latter compounds raised the DA levels notably in combination with haloperidol. Sertindole and risperidone significantly increased the extracellular levels of ACh but only sertindole raised the extracellular levels of Glu. The selective 5-HT(6) receptor antagonist, SB-271046, significantly increased the extracellular levels of Glu.
Conclusion: Sertindole and risperidone markedly increased extracellular levels of DA in mPFC. The built-in 5-HT(2A)/5-HT(2C)/D(2) receptor antagonism of the two drugs might be involved in this action. Both drugs increased the extracellular levels of ACh but only sertindole enhanced Glu levels. The high affinity of sertindole for the 5-HT(6) receptor compared to risperidone may differentiate sertindole from risperidone.