Correlation between estrus and reduced light avoidance in mice

Female CD-1 mice showed reduced light avoidance at estrus compared to nonestrus in two experiments designed to control for possible effects of changes in general activity. Estrous mice were quicker to enter a light chamber from a dark chamber and slower to enter a dark chamber from a light chamber, than nonestrous mice. Also, estrous mice reared up on their hind legs more frequently than nonestrous mice in the light chamber, and there was no difference between estrous and nonestrous mice in motor activity in the dark chamber. These findings, along with previous findings of reduced shock avoidance at estrus, suggest a general decrement in avoidance motivation which may be adaptive to the process of mating and which does not appear to be secondary to a change in activity level.