Facilitation of delayed alternation performance in adult rats following chronic hydroxyzine treatment in infancy

Abstract

Hydroxyzine is a minor tranquilizer commonly employed in pediatric medicine. In the present study, rats were given daily oral doses of hydroxyzine (40 mg/kg) or sucrose vehicle placebo from age 10 to 35 days. In adulthood, rats that had been treated with hydroxyzine were significantly superior to littermate controls in delayed spontaneous alternation and delayed alternation learning; however, there were no observable differences in spontaneous alternation performance when no delay was imposed between trials. The facilitatory effect may be due to modification of the developing limbic system; by whatever mechanism, present results indicate that even minor tranquilizers administered in infancy may produce permanent behavioral changes. Since task-specific facilitation may reflect neural malfunction as well as overall improvement in learning capacity, it may be wise to exercise greater caution in the use of such drugs in pediatric medicine.