Facilitation of delayed spontaneous alternation behavior in adult rats following early hydroxyzine treatment: differential sensitivity in late infancy.

When tested in adulthood, male rats that had been treated daily with 50 mg/kg hydroxyzine HCl SC at 10--29 or 23--29 days of age were significantly facilitated in performance of delayed spontaneous alternation relative to saline-injected rats. Treatment at 10--16 days of age did not produce significant facilitation in the delay task, nor were there any significant differences between groups in spontaneous alternation with no intertrial delay. The facilitative effect may be attributable to anomalies in areas, such as the limbic system, that continue to develop postnatally and mature in late infancy.