Blue light regulates the expression of brain derived neurotrophic factor in the habenula nucleus of depression-like rats induced by light deprivation

Abstract

Objective: To investigate the regulatory effect of blue light on the expression of brain derived neurotrophic factor (BDNF) in the habenula nucleus of depression-like rats induced by light deprivation. Methods: male SD rats were exposed to white light (white light control group, 20 rats) and constant darkness (depression model group, 60 rats), respectively. 18 days later rats in depression model group were randomly divided into three groups: depression model group (treated with constant darkness), blue light group (treated with blue light) and red light group (treated with red light). Rats in white light control group were kept in white light. All rats exposed to light were in a standard 12∶12 h Light/Dark condition at 20 lx for 36 days. Sucrose preference test was applied to evaluate depression-like symptoms of rats. The c-fos+cells in the habenula nucleus, intergeniculate leaflet and ventral lateral geniculate nucleus were detected. The phosphoylation of cAMP-response element binding protein (CREB) and the relative BDNF protein level in the habenula nucleus were measured. Results: Sucrose intake per kg body weight increased in rats exposed to blue light and returned to the level of control group (P>0.05). Sucrose intake per kg body weight in red light group and depression model group were lower than control group (P<0.05). More c-fos+cells were detected in the habenula nucleus, intergeniculate leaflet and ventral lateral geniculate nucleus from blue light group than those from depression model group (P<0.05). The relative BDNF protein level and the phosphoylation of CREB in the habenula nucleus from blue light group were higher than those from depression model group (P<0.05). Conclusion: Blue light could relieve depression-like symptoms in light-deprived rats. Exposure to blue light could activate neurons in the habenula nucleus to which intrinsically photosensitive retinal ganglion cells projected. Blue-light-mediated antidepressant effect might involve in the activation of CREB/BDNF signal transduction pathways in the habenula nucleus.