Abstract
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.
Key words
cognition - unpredictable chronic mild stress - gene expression - tianeptine - olanzapine
- fluoxetine