Cortical-striatal integration of cocaine history and prefrontal dysfunction in animal modeling of dual diagnosis.

Background: High rates of substance disorders in schizophrenia and other mental illnesses may reflect biological vulnerabilities to the addiction process. Interactions between addictive drug effects and mental illness involving circuits that generate motivated behavior may underpin this vulnerability.

Methods: We examined separate and combined effects of neonatal ventral hippocampal lesions (NVHLs)-a neurodevelopmental model of schizophrenia (vs. SHAM-operated control animals)--and a behaviorally sensitizing cocaine history (15 mg/kg/day x 5 days vs. saline injections) on acute cocaine-induced neural activation signaled by c-Fos expression. Stereological assessment of activation densities spanned six ventral to dorsal cortical-striatal compartments.

Results: Cortically, NVHLs showed hypoactivation and decreased volume of the ventral medial prefrontal cortex. In contrast, cocaine history was only expressed subcortically and as a hyperactivating effect in the dorsal striatum where significant NVHL-induced hyperactivation also emerged. Across all subjects and brain regions, only dorsal striatal activation was correlated with differences in sensitized locomotion. However, this activation was tightly correlated to a simple multiplicative function of ventral medial prefrontal hypoactivation and cocaine history-related increases in striatal activation.

Conclusions: These findings suggest drug history and developmental temporal limbic abnormalities associated with prefrontal dysfunction produce compounding effects within cortical-striatal circuits as mechanistic basis for dual diagnosis.