Increased ethanol self-administration in developmentally low-level lead exposed rats: voluntary intake vs. operant conditioning
Mara S. Mattalloni, Laura De Giovanni, Liliana M. Cancela and Miriam B. Virgolini
IFEC-CONICET. Depto. de Farmacología. Facultad de Ciencias Químicas. Universidad Nacional de Córdoba. Córdoba. Argentina.
Several evidences demonstrate an interaction between lead (Pb) and drugs of abuse, particularly ethanol. This study aimed to investigate the influence of perinatal low-level Pb exposure on the motivational properties of ethanol by using a two-bottle ethanol/water test and an operant oral ethanol self-administration task. Thirty-five day-old male pups perinatally exposed to 220 ppm Pb were evaluated in their ethanol intake in a free-choice limited paradigm (2 h) at increasing ethanol concentrations (2-10%). Another group of animals was trained to associate the contingency of a lever press with 10% ethanol administration under a fixed-ratio 1 (FR 1) schedule of behavior, which was increased progressively across sessions to FR2, 5, 10, and 20. The results demonstrated that Pb-exposed rats voluntarily consumed more ethanol than their respective controls. Interestingly, the amount of ethanol ingested was sufficient to induce hyperlocomotion, as assessed immediately after the last ethanol (10%) intake session. We also demonstrated that Pb-exposed animals worked harder than the controls to obtain ethanol, evidencing a ?break point? at higher lever-press rates. These results are indicative of higher ethanol reinforcing properties in low-level Pb exposed rats as compared to controls.
