Differential effects of photic stimulation of different wavelengths on behavioral despair in male and female wistar rats

Abstract

There is ample evidence in both humans and animals that light therapy has ameliorative effect on depression and behavioral despair. However, there is a paucity of studies investigating the mechanism of light treatment using animal models of depression. The present study therefore investigated the effects of light stimulation of different wavelengths presented in the late dark phase of an L/D lighting cycle on behavioral despair. Adult male Wistar rats were randomly assigned to a control and two experimental groups (n=8 for each). Animals were exposed to a 10-min pulse in the blue or red region of the visible spectrum, late in the dark phase of the L/D cycle (0400 h) at approximately 1300 lux. This manipulation was followed by forced swim test (FST) procedure starting from the very next day. Moreover, light induced c-Fos immunoreactivity in the Suprachiasmatic Nucleus (SCN) had been investigated to assess the subdivisions involved in the process. Results of the present study indicated that a short pulse of blue light has ameliorative effect for male rats, but not for female rats. Moreover, blue and red light administration aggrandized c-Fos immunoreactivity in the ventrolateral region of the SCN.