BEHAVIORAL AND NEUROCHEMICAL CONSEQUENCES OF NEONATAL EXPOSURE TO LEAD IN RATS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 2  (2) , 473-484
Abstract
Locomotor activity, Pb content and concentrations of norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in discrete brain regions were examined in rats given a fixed oral dose (50 .mu.g/pup) of inorganic Pb from birth until weaning and kept on H2O containing 80 ppm Pb until 8 or 12 wk of age. Pb-exposed animals showed an increase (by 74 and 93%, respectively) in locomotor activity at 6 and 8 wk of age. By 12 wk, the motor activity returned to control values in animals which were withdrawn from Pb treatment at 8 wk of age and in those continued on Pb. Pb levels in brain at 8 wk of age were highest in hypothalamus and striatum. Significant decreases in cortical NE, DA and 5-HT, midbrain DA, striatal NE and hypothalamic DA and 5-HT were found in brains of 8 wk old hyperactive rats; NE levels in the midbrain were elevated. Whereas the decreases in 5-HT remained unchanged, alterations in regional concentration of catecholamines were no longer evident in Pb-exposed animals whose motor activity returned to normal by 12 wk of age or in rats withdrawn from Pb at age of 8 wk. Alterations in regional levels of NE and DA appear associated with Pb-induced increase in locomotor activity, while changes in 5-HT metabolism may result from a non-specific toxic effect of the metal.