EFFECTS OF PRENATAL COCAINE EXPOSURE ON THE MESOCORTICOLIMBIC DOPAMINE SYSTEM - AN IN-VIVO MICRODIALYSIS STUDY IN THE RAT

Microdialysis studies were conducted on prenatally saline-treated and prenatally cocaine-treated rats, either as pups (10-30 days old) or yo ung adults (40-190 days old), to study the effects of prenatal cocaine exposure on the mesolimbic dopamine (DA) system. In the n. accumbens of saline-treated rats, basal dialysate concentrations of DA were simi lar in pups and adults; however, the levels of DA metabolites, DOPAC, HVA, and the serotonin metabolite, 5-HIAA, were markedly lower in pups . In pups, prenatal cocaine exposure led to basal dialysate levels of DA in the n. accumbens that were twice control levels; however, there was no difference in response to a period of intermittent tail pinch o r an acute injection of cocaine (20 mg/kg). In the adult, basal levels of DA, DOPAC, HVA and 5-HIAA in n. accumbens did not differ across pr enatal treatments. However, in prenatally cocaine-treated adults a coc aine injection led to an enhanced rise in extracellular DA compared to controls. In frontal cortex of adult rats, basal levels of DA, DOPAC and HVA did not differ across prenatal treatments; however, basal leve ls of 5-HIAA in this region were significantly elevated in prenatal-co caine rats. No group differences were observed in the frontal cortex i n response to either tail pinch or cocaine. Thus prenatal cocaine expo sure produces an increase in basal extracellular DA in the n. accumben s of pups which returns to normal with aging. While this initial diffe rence normalizes, prenatal cocaine exposure induces other persistent c hanges in adulthood.