Chronic interferon-α decreases dopamine 2 receptor binding and striatal dopamine release in association with...

Neuroimaging studies in humans have demonstrated that inflammatory cytokines target basal ganglia function and presynaptic dopamine (DA), leading to symptoms of depression. Cytokine-treated nonhuman primates also exhibit evidence of altered DA metabolism in association with depressive-like behaviors. To further examine cytokine effects on striatal DA function, eight rhesus monkeys (four male, four female) were administered interferon (IFN)-α (20 MIU/m(2) s.c.) or saline for 4 weeks. In vivo microdialysis was used to investigate IFN-α effects on DA release in the striatum. In addition, positron emission tomography (PET) with [(11)C]raclopride was used to examine IFN-α-induced changes in DA2 receptor (D2R) binding potential before and after intravenous amphetamine administration. DA transporter binding was measured by PET using [(18)F]2β-carbomethoxy-3β-(4-chlorophenyl)-8-(2-fluoroethyl)nortropane. Anhedonia-like behavior (sucrose consumption) was assessed during saline and IFN-α administration. In vivo microdialysis demonstrated decreased release of DA after 4 weeks of IFN-α administration compared with saline. PET neuroimaging also revealed decreased DA release after 4 weeks of IFN-α as evidenced by reduced displacement of [(11)C]raclopride following amphetamine administration. In addition, 4 weeks of IFN-α was associated with decreased D2R binding but no change in the DA transporter. Sucrose consumption was reduced during IFN-α administration and was correlated with decreased DA release at 4 weeks as measured by in vivo microdialysis. Taken together, these findings indicate that chronic peripheral IFN-α exposure reduces striatal DA release in association with anhedonia-like behavior in nonhuman primates. Future studies examining the mechanisms of cytokine effects on DA release and potential therapeutic strategies to reverse these changes are warranted.