The Expression of Brain-Derived Neurotrophic Factor and Tryptophan Hydroxylase in the Dorsal Raphe Nucleus during Repeated Stress

Abstract

The mechanisms of development of stress-induced depression symptoms may include interaction between the elements of the serotonergic (5-HT) system and brain-derived neurotrophic factor (BDNF) at the level of the cell bodies of 5-HT neurons. In order to evaluate this situation, we used immunofluorescent staining of BDNF protein and the enzyme of serotonin synthesis tryptophan hydroxylase (TPH) in the dorsal raphe nucleus (DRN) of adult male rats that were subjected daily to a 15-min forced swim stress for 1, 2, 7, or 14 days. The expression of the BDNF protein was substantially decreased in the DRN after 7- or 14-day stress, whereas the expression of the TPH protein significantly increased after the 14-day stress and did not differ from the control after the shorter duration of repeated stress. The absence of correlation between some indices indicates their independence from each other at the level of the cell bodies of 5-HT neurons.