Evaluation of cognitive function of fluoxetine, sertraline and tianeptine in isolation and chronic unpredictable mild stress-induced depressive Wistar rats

Depressive illness is generally associated with cognitive impairment. Serotonergic selective antidepressant drugs, fluoxetine (FLX), sertraline (SER) and tianeptine (TIA), are claimed to have less or no effect on cholinergic system, the key system involved in memory. In the present study, these drugs were evaluated for their influence on cognitive behavior in both depressive and non-depressive animals. Depression was induced by two models, (i) 60 days social isolation of litter; and ii) by applying chronic unpredictable mild stress for 21 days. Depression in the rats was confirmed by behavioral despair test. Transfer latency on elevated plus maze and inflexion ratio in passive avoidance step through behavior were employed to assess learning and memory. The results indicated that administration of fluoxetine; sertraline and tianeptine attenuated the cognitive deficits observed in depressive rats. In non-depressive rats these drugs produced retention deficit, which was found to be parameter and model dependent. Data suggested that, FLX and SER (SSRI's) effectively attenuated the isolation-induced depression and cognitive deficit, whereas TIA (SSRE) produced better effect in stress-induced depressive conditions. It was concluded that behavioral profiles of fluoxetine, sertraline and tianeptine on cognition were model and parameter dependent.