Alteration of brain cell membrane function following cocaine exposure in the fetal guinea pig

The effect of cocaine on brain cell membrane structure and function was studied in the fetal guinea pig. We tested the hypothesis that cocaine, a potent vasoconstrictor, would result in brain cell membrane dysfunction as determined by altered activity of Na⁺,K⁺-ATPase and the appearance of products of membrane lipid peroxidation (conjugated dienes (CD) and fluorescent compounds (FC)). A total of 14 pregnant guinea pigs were studied at term (60 days). One hour prior to delivery, the pregnant guinea pigs were divided into 3 groups as follows: cocaine, 30 mg/kg i.p., saline placebo i.p., or 7% FiO₂ for 1 h. Following cocaine, brain Na⁺,K⁺-ATPase activity decreased (mean ± S.D., 25.6 ± 9.2 vs. 54.6 ± 3.4 μmol P_i/mg protein/h, cocaine vs. control, respectively, (P < 0.01) and was similar to the hypoxia group (21.9 ± 2.8 μmol P_i/mg protein/h). The products of lipid peroxidation did not change significantly following cocaine hypoxia resulted in a rise in CD from 0 to 0.175 ± 0.015 μmol/g brain, control vs. hypoxia, (P < 0.01), and FC from 1.13 ± 0.15 to 1.88 ± 0.13 μg quinine sulf brain, control vs. hypoxia, (P < 0.01). These data show that acute fetal cocaine exposure, unlike hypoxia alone, results in a significant decrease in Na⁺,K⁺-ATPase activity without a significant increase in the products of lipid peroxidation, suggesting the mechanism by which cocaine affects brain cell membrane integrity is distinct from hypoxia. Inhibition of the enzyme activity may be due to a direct action of cocaine on the enzyme or due to enzyme regulation by cocaine-induced alterations in neurotransmitters.