Long-term effects of cariprazine exposure on dopamine receptor subtypes

Abstract

IntroductionAll clinically effective antipsychotics are known to act on the dopaminergic system, and previous studies have demonstrated that repeated treatment with antipsychotics produced region-specific changes in dopamine receptor levels. Cariprazine is a dopamine D3 and D2 receptor partial agonist with preferential binding to D3 receptors. We examined the effects of chronic cariprazine administration on dopamine receptor levels.MethodsRats were administered either vehicle or cariprazine (0.06, 0.2, or 0.6 mg/kg) for 28 days. Dopamine receptor levels were quantitated using autoradiographic assays on brain tissue sections from the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), caudate putamen (CPu), hippocampus (HIPP), olfactory tubercle (OT), and islands of Calleja (ICj).ResultsChronic treatment with cariprazine did not alter D1 receptor levels in any brain region tested. Cariprazine increased D2 receptor levels in mPFC (27%–43%), NAc (40%–45%), medial (41%–53%) and lateral (52%–63%) CPu, and HIPP (38%). Cariprazine dose-dependently upregulated D3 receptor levels in ICj (32%–57%), OT (27%–67%), and NAc shell (31%–48%). Repeated cariprazine treatment increased D4 receptor in NAc (53%–82%), medial (54%–98%) and lateral (58%–74%) CPu, and HIPP (38%–98%).ConclusionSimilar to other antipsychotics, cariprazine upregulated D2 and D4 receptor levels in various brain regions. Cariprazine was unique among antipsychotics in increasing D3 receptor levels, which may support its unique psychopharmacologic properties.