Ethanol self-administration in rats following exposure to dietary cadmium

Rats were maintained on an ad lib diet containing 100 ppm cadmium (Group Cadmium-Diet) or a control diet with no added cadmium (Group Control-Diet). After 55 days of exposure to their respective diets, animals were tested for fluid intake using a nonchoice procedure that presented a 15% ethanol solution in the home cage for 5 days. Subsequently, all animals were offered a 10% ethanol solution or tap water in a 3-bottle, 2-fluid choice test in the home cage. This fluid intake test was conducted for a 5 day baseline period, and then again concurrently with avoidance acquisition (14 days) and extinction (4 days) training on a free operant (Sidman) avoidance task that required animals to lever press to avoid electric footshock. After training was terminated the choice test was continued further in the home cage for a 15 day post-avoidance period. Ethanol intake was greater for animals exposed to cadmium on all tests of fluid consumption, and all animals consumed more ethanol during the periods following termination of the stressor (avoidance extinction, post-avoidance) than during the actual period of stress (avoidance acquisition). Interpretive comments focus on the effects of cadmium on stress reactivity, sensory processing, and metabolism.