Hyperresponsiveness to methylphenidate in rats following prenatal ethanol exposure.

Rats exposed in utero to ethanol are hyperresponsive to methylphenidate when tested as neonates or adults. Long-Evans rats were maintained on liquid diets containing either ethanol or maltose-dextrin (35% of total calories) or on lab chow and water throughout pregnancy. Male offspring, who were raised by foster mothers maintained on lab chow and water throughout pregnancy and lactation, were used in two experiments to examine the effects of methylphenidate on activity. In Experiment 1, a time-sampling procedure revealed that methylphenidate (0, 1, 2 & 4 mg/kg) increases the frequency of ambulation in young (26-38 day old) ethanol-treated offspring more than in control offspring. In Experiment 2, an open-field procedure revealed that methylphenidate (0, 2, 4, 6 & 8 mg/kg) produces greater increases in number of squares covered and the total duration of ambulation during 5-min tests in adult (100-184 day old) offspring treated prenatally with ethanol than in control offspring. Both studies revealed that the hyperactivation effect increases with increased doses of methylphenidate.