Gender differences in prodynorphin but not proenkephalin mRNA expression in the striatum of adolescent rats exposed to prenatal cocaine.

The objective of this study was to determine if prenatal cocaine affects the levels of prodynorphin and proenkephalin mRNA in male and female adolescent rats. Pregnant dams received cocaine or vehicle from gestational days 8-22 and upon delivery, the pups were fostered. At postnatal days 42-44, pups were killed and brains removed and frozen. Sections of striatum and nucleus accumbens were processed for prodynorphin and proenkephalin mRNA expression. Prenatal cocaine did not affect the expression of proenkephalin mRNA, but males showed higher expression than females. However, prodynorphin mRNA was lower in female rats exposed to cocaine compared to controls. Prenatal cocaine appears to have unique effects on neuropeptides during adolescence.