Effects of forced swimming stress on rat brain function.

Chronic stress has been reported to be an essential factor for depression. In this study, the effect of forced swimming stress on neurotransmitters and cellular signaling pathway contributing to brain functions was investigated using the forced swimming test (FST) in order to understanding of mechanisms to regulate stress signals in brain. Antidepressant drug, imipramine, significantly reduced the immobility time of male rats in the FST by 85% at a dose of 15 mg/kg for 2 weeks. This result indicated that the swimming stress caused a depressed state in the rats without administration of imipramine. Swimming stress significantly lowered the serotonergic ratio and also markedly enhanced the phosphorylation of ERK1/2 in the hypothalamus region compared to the rats without FST. These phenomena may be included in key mechanisms of the development of depression.