Effects of light intensity on passive avoidance behavior of male and female Wistar rats.

Groups of intact male and female Wistar rats were exposed to a standard passive avoidance procedure. The intensity of the light bulb illuminating the platform during adaptation, pre- and post-shock trials was manipulated (5, 25 or 75 W). Entrance latencies during pre-shock trials were longer for males than for females. They decreased for both males and females as light intensity was increased. Entrance latencies increased over trials for males but not for females. On the post-shock trial, more females than males reentered the compartment in which they previously had been shocked, with shorter entrance latencies. Thus, although light intensity functionally affected the behavior of males and females on pre-shock trials, it did not influence the behavioral differences usually observed on the post-shock trial. These data are interpreted as further evidence for the notion that the behavior of male Wistar rats in standard passive avoidance procedures is a function of non-specific effects of shock presentation per se. It is suggested that research aimed at understanding basic (neuronal) differences between males and females is necessary to be able to specify the nature of the variables responsible for the observation of behavioral differences between males and females in this and other experimental paradigms.