Altered behavioral response to apomorphine in cadmium exposed rats

The present study investigated the hypothesis that changes in dopamine system functioning mediates cadmium induced hyperactivity. Two groups of twenty male Sprague-Dawley rat pups were treated with either 0.25 mg/kg of CdCl2 in saline or the saline vehicle only for ten consecutive days beginning on the fifth day of life. Beginning at 50 days of age, locomotor activity was recorded following each of three different doses of apomorphine HCl in saline or the saline vehicle only. Results indicated a significant cadmium by dose of apomorphine interaction when groups were first divided into high and low activity groups on the basis of baseline activity scores. These results are interpreted as indicating the existence of dopamine system supersensitivity in cadmium exposed animals. However, differences between treatment groups in baseline activity levels were not observed thus the relationship between alterations in DA system-functioning and Cd-induced hyperactivity could not be confirmed. In addition, a significant decrease in the body weights of Cd treated animals appeared approximately two weeks after the cessation of treatment and persisted through the testing period. Alternate hypothesis which might explain the observed behavioral differences are discussed.