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

Abstract

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.

Figure 1

Prodynorphin mRNA expression (dpm/mg) in adolescent males (A) and females (B) exposed to prenatal cocaine. For this and subsequent figures, numbers for the caudate-putamen and nucleus accumbens correspond to distance from Bregma based on Paxinos and Watson (2004). Here and in all other figures, bars represent mean ± SEM. N’s are 12 males and 10 females from 6 cocaine-treated litters and 12 males and 11 females from 6 control litters..

Figure 2

Proenkephalin mRNA expression (dpm/mg) in adolescent males (A) and females (B) exposed to prenatal cocaine. N’s are as for figure 1.

Figure 3

Prodynorphin (A) and proenkephalin (B) mRNA expression levels collapsed for all regions analyzed. * represents significantly lower than same sex control; ^ represents significantly higher than all other groups; # represents both groups of males significantly different than both groups of females.