Density of α2-adrenergic receptors in laconosum-moleculare layer of hippocampal area CA1 as measured by autoradiography. Data are expressed as mean density (± S.E.M.). In control animals prenatally exposed to saline, the density of hippocampal CA1 α2-adrenergic receptors in male rats was significantly [F(1, 52) = 23.2; P < 0.0001] lower than the density of α2-adrenergic receptors observed in female controls. Prenatal cocaine exposure abolished this sex difference in hippocampal α2-adrenergic receptors by increasing binding 21% in male offspring, whereas α2-adrenergic receptors did not significantly differ by drug exposure in females. n = 14 per group.