Elevated anxiety and depressive-like behavior in a rat model of genetic generalized epilepsy suggesting common causation.

The explanation for the increased prevalence of neuropsychiatric disorders in epilepsy patients is uncertain, with both biological and psychosocial factors proposed. Increasing evidence supports the idea of shared neurobiological processes leading both to seizures and to behavioral, emotional and cognitive disturbance. This study addresses this using Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a model of human generalized epilepsy. We subjected GAERS (n=47) and Non-Epileptic Control rats (NEC; n=73) to behavioral measures of depression and anxiety at 7 and 13 weeks of age, ages prior to and after seizure onset. We employed the Sucrose-Preference Test (SPT), the Elevated Plus Maze (EPM), and the Open Field Arena (OFA). GAERS exhibited significantly greater levels of both depression- and anxiety-like behaviors on all measures, including reduced consumption of sucrose solution in the SPT; lower percentage of time in the open arms of the EPM; and reduced exploratory activity and less time spent in the inner area of the OFA. These differences were evident at both 7 and 13 weeks of age, before and after the onset of epilepsy. Increased anxiety- and depressive-like behaviors are observed in GAERS. These behavioral differences exist before the onset of seizures indicating that they are not secondary consequences of seizures, and suggest shared factors in the biological diathesis underlying the two kinds of disorder. Studying affective disturbance in animal models of epilepsy may illuminate the pathogenesis of affective disorder more generally, as well as modeling psychiatric comorbidities common in epilepsy patients.