Early effects of lurasidone treatment in a chronic mild stress model in male rats.

Rationale: Stress represents a major contributor to the development of mental illness. Accordingly, exposure of adult rats to chronic stress represents a valuable tool to investigate the ability of a pharmacological intervention to counteract the adverse effects produced by stress exposure.

Objectives: The aim of this study was to perform a time course analysis of the treatment with the antipsychotic drug lurasidone in normalizing the anhedonic phenotype in the chronic mild stress (CMS) model in order to identify early mechanisms that may contribute to its therapeutic activity.

Methods: Male Wistar rats were exposed to CMS or left undisturbed for 7 weeks. After two weeks of stress, both controls and CMS rats were randomly divided into two subgroups that received vehicle or lurasidone for five weeks. Weekly measures of sucrose intake were recorded to evaluate anhedonic behavior, and animals were sacrificed at different weeks of treatment for molecular analyses.

Results: We found that CMS-induced anhedonia was progressively improved by lurasidone treatment. Interestingly, after two weeks of lurasidone treatment, 50% of the animals showed a full recovery of the phenotype, which was associated with increased activation of the prefrontal and recruitment of parvalbumin-positive cells that may lead to a restoration of excitatory/inhibitory balance.

Conclusion: These results suggest that the capacity of lurasidone to normalize anhedonia at an early stage of treatment may depend on its ability to modulate the function of the prefrontal cortex.