Long term reduction in eight arm maze performance after early exposure to phenobarbital.

Performance in the hippocampal eight arm maze was studied in mice after early exposure to phenobarbital (PhB). since previous studies suggested that these animals suffered neural deficits in the hippocampus. For prenatal exposure pregnant mothers were fed 3 g PhB/kg milled food on gestation days 9-18. Neonates were injected daily with 50 mg PhB/kg. on postnatal days 2-21. After a week of water deprivation, the animals were tested at age 50 days for 5 days preceded by 1 day of habituation. Deficits in eight arm maze performance were demonstrated in early treated mice on every testing day. For example, on day 5 of testing the number of correct entries during the first eight attempts in the prenatally treated group were 12% below control level (P<0.01), the respective reduction in the neonatal group was 10% (P< 0.001). The number of trials needed to enter all arms on day 5 was 27% above control level among prenatally treated mice (P< 0.001), and 13% in neonatally treated mice (P< 0.05). It took prenatal PhB animals twice the time to reach criterion than their controls (P< 0.001) and four times as long for neonatally treated mice (P< 0.001).