Genotype-treatment interaction in response of mice to early barbiturate administration

Results of this investigation show a differential effect of early barbiturate administration on behaviors of mice of two inbred strains in the open field and in the barrier cage. Pups of the inbred strains DBA/l and C57BL/10 were fostered by HS/Ibg dams and were given a daily injection of 50 mg/kg sodium phenobarbital on postnatal days 2-21 (treated groups); control pups received vehicle injections. At 28 and 30 days the animals were tested in an open field and in a barrier cage. The DBA/l mice responded differently from C57BL/10 to early barbiturate treatment. Treated DBA/l mice showed a marked reduction from control levels in open-field locomotion and grooming but not in defecation. In the barrier test, there were reductions in jumping, peeking and grooming and increase in defecation. The differences between controls and treated in the C57BL/10 strain were small except for barrier jumping and peeking. It is suggested that genotype (strain) - environment (drug) interaction exists for the effect of early phenobarbital administration on behavior: DBA/l was sharply affected by the drug, while the behavior of C57BL/10 was little altered by neonatal phenobarbital administration.