Prenatal alcohol exposure and offspring hyperactivity: effects of para-chlorophenylalanine and methysergide.

Pregnant Wistar rats were exposed to either a liquid diet containing ethanol, pair-fed an identical diet with sucrose substituted for ethanol, or received ad lib chow and water, during days 6-19 of gestation. Pups were injected with a dose of 100 mg/kg of para-chlorophenylalanine, 48 hr, 24 hr or immediately prior to activity testing at 16, 22 or 28 days of age. Further groups were injected with isotonic saline just prior to activity testing. Pups exposed to alcohol prenatally were more active than controls at 16 days of age. parachlorophenylalanine brought about significant increases in activity when injected 24 or 48 hr prior to testing in 16-day-old pups, and significant increases in activity when injected 24 hr prior to testing in 22- and 28-day-old pups. However, these effects of parachlorophenylalanine were similar regardless of prenatal treatment. In a second study, 16-day-old pups received saline, 0.5, 1.0 or 2.0 mg/kg of methysergide immediately prior to an activity test. Methysergide brought about a dose-related decrease in activity in all three groups of pups. Most importantly, the effects on activity of the methysergide were similar regardless of the treatment received during gestation. These data indicate that the hyperactivity associated with fetal alcohol exposure is unlikely to result from alterations in the ontogeny of a serotonergic system involved in response inhibition.