The effects of tianeptine, olanzapine and fluoxetine on the cognitive behaviors of unpredictable chronic mild stress-exposed mice.

BACKGROUND

Strong evidence indicates that impaired cognition is a core element of depression, and antidepressant treatment may ameliorate cognitive impairments experienced by depressive patients. Present study was performed to investigate effects of chronic tianeptine (5 mg/kg) or olanzapine (2.5 mg/kg) administration on cognitive behaviors of unpredictable chronic mild stress (UCMS)-exposed mice and to compare these effects to those induced by widely used SSRI antidepressant fluoxetine (15 mg/kg) in mice.

METHODS

To investigate effects of these drugs, the Morris water maze test (MWM), elevated plus maze test (EPM) and radial arm maze test (RAM) were used. The effects of stress and drugs on gene expression in the hippocampus was determined by quantitative Real Time-PCR.

RESULTS

In MWM test, fluoxetine significantly increased escape latency of non-stressed mice in acquisition sessions and decreased time spent in escape platform quadrant in probe trial; tianeptine and olanzapine decreased enhancement in escape latency, and only olanzapine significantly enhanced attenuation in time spent in the escape platform quadrant in UCMS-exposed mice. In EPM test, all drugs significantly decreased enhancement in transfer latency in UCMS-exposed mice. In RAM test, fluoxetine significantly increased number of errors made by both non-stressed and UCMS-exposed mice.

CONCLUSION

Quantitative real-time PCR revealed that CREB and BDNF gene expression levels were significantly decreased in UCMS-exposed group, and this effect was significantly reversed by each of drugs tested. Our results seem to be test dependent and should be further investigated using different learning and memory tasks.