[The effects of duloxetine on beta-actin stress response in rat brain]

Depression is a frequent prodromal symptom of Alzheimer's disease (AD). Stress factors play an important role in the etiopathology of both diseases, since increased corticosteroid levels caused by chronic stress indirectly induce neuronal damage. The aim of our experiments was to evaluate the changes induced by stress in the transcription of amyloid precursor protein (APP), mitogen activated protein kinase-1 (MAPK-1) and beta-actin, of which the latest plays a leading role in synaptic plasticity. Additionally we intended to examine how duloxetine - a serotonin-norepinephrin reuptake inhibitor type antidepressant - would modify the stress-induced changes. Wistar rats were exposed to immobilization stress for five hours daily through 21 days, while part of the animals received 45 mg/bwkg of duloxetine. At the end of the third week total RNA was purified from the cortex and hippocampus. The amount of beta-actin, APP and MAPK-1 mRNA was determined by real time PCR method. On protein level, semiquantitative measurement was performed by Western blot. The expression of beta-actin mRNA in the animals exposed to stress was four times as intense as in the control group. The increase in the beta-actin mRNA levels was repressed by the duloxetine treatment. In the case of APP and MAPK-1 no changes were detected. According to the Western blot results, the antidepressant treatment slightly, the drug along with the stress treatment strongly decreased the amount of the beta-actin protein. Our findings indicate that antidepressant treatment with duloxetine could play a protective role against the chronic stress-induced changes in the nervous system, such as disorders of synaptic plasticity, and the consequent cognitive dysfunctions in case of both affective disorders and AD.