Lessened sensitivity to apomorphine induced climbing behavior in mice following neonatal exposure to phenobarbital

Heterogeneous HS/Ibg mice were injected daily with 50 mg/kg phenobarbital (PhB) from age 2 to 21 days (B group), while control litter mates received vehicle injections. Control and a B mice were then tested for striatal climbing behavior induced by 2 or 5 mg/kg apomorphine, at ages 22, 28, 35 or 44 days. At age 22 days B mice had reductions of climbing from control levels of 44% and 41% for 2 and 5 mg apomorphine respectively (p less than 0.01), regardless of sex differences. On day 28 the respective reductions were 16% and 32% (p less than 0.05). The differences on days 35 and 44 were small and did not reach statistical significance. Since climbing has been found to be induced primarily by postsynaptic striatal dopaminergic receptors, it is suggested that neonatal exposure may reduce the behaviors mediated by striatal postsynaptic dopamine receptors. The present findings support other studies implicating postsynaptic striatal dopamine receptors in the behavioral alterations induced by early PhB exposure.