Effect of chronic exposure to lead on GABA binding in developing rat brain.

The effect of chronic treatment with lead on the growth and the development of calcium-dependent GABA(B) (forebrain and cerebellum) and calcium-independent GABA(A) binding (forebrain), at 10, 21 and 84 days post-natally (PN), was studied in rats whose dams received either lead acetate (7 gl(?1), 18.5 mM) or sodium acetate (controls) in their drinking water from conception to weaning and normal animals given only water. The body and brain weight of lead treated pups was significantly less than that of normal and control pups. Chronic lead treatment produced receptor specific effects on binding at different times during development. In the forebrain GABA(A) binding was reduced at PN 10 (decreased affinity and density) but showed increased receptor density at PN 84. GABA(B) binding, while reduced during the developmental period (increased affinity and decreased density), appeared to have recovered at maturity. The development of cerebellar calcium-dependent binding was more variable in showing an increase in affinity in adult animals and decreased density at PN 10 and 84. There was no difference in normal and control binding except at PN 10 for both GABA(A) and GABA(B) binding. Chronic lead treatment affects calcium-dependent and calcium-independent binding differently suggesting that within the period of greatest vulnerability to the effects of lead, development in different receptor systems may be affected in quite different ways according to the role of calcium in their normal function.