Effect of reversed light-dark cycle on skin conductance in male rats

Reversal of light-dark cycle was used to investigate the effect of the circadian changes on skin conductance, a tonic electrodermal activity parameter, in rats. Rats were adapted for 3 wk. to one of two lighting programs. The animals on the normal cycle were illuminated from 08.00-20.00; on the reverse cycle, from 20.00-08.00. Although during Week 1 to Week 3, skin conductance increased gradually in both groups, this increase was more dramatic in rats adapted to light from 20.00 to 08.00 than in the other group. When the animals on the reverse cycle were readjusted to a normal circadian cycle for 3 weeks, skin conductance decreased gradually to initial values. At Weeks 1, 2, 3, and 6, skin conductance was significantly higher in rats on the reverse light-dark cycle than in those on the normal cycle. The present data suggest that changes in normal light-dark conditions affect skin conductance in rats.