Cocaine concentrations in fetal C57BL/6 mouse brain relative to maternal brain and plasma

Cocaine concentrations in maternal plasma and brain and fetal brain of mice were evaluated as a model for fetal brain exposure during maternal cocaine use. On days 12-18 of gestation, mice (C57BL/6; N = 5-7/group) received SC cocaine-HCI: 20 or 40 mg/kg. Maternal plasma and brain (accumbens and caudate nuclei removed), and fetal brain were collected at 0.5, 1, and 2 h following the last injection. Analysis was by GC-MS. Brain cocaine levels in the dams declined from 9.6 to 3.4 and 20.9 to 12.5 micrograms/g [corrected] during the 0.5-1-h period after the low and high doses, respectively, and were 7.5-14.3 times greater than plasma levels. The corresponding fetal brain concentrations changed from 1.6 to 1.3 and 2.9 to 3.4 micrograms/g [corrected]. By 2 h, brain cocaine concentrations in dams declined to approximately 10% of their 0.5-h values, with a slower drug decay occurring in fetal brain. Maternal plasma cocaine concentrations correlated with those of maternal brain (r = 0.94, p < 0.01) and fetal brain (r = 0.69, p < 0.01). The present results indicate that cocaine accumulates to a lesser extent in fetal brain than in maternal brain of C57BL/6 mice; however, the duration of exposure appears to be more sustained in the fetus, a phenomenon that may have toxicological implications for human in utero cocaine exposure.