The effect of perinatal lead administration on the ontogeny of striatal enkephalin levels in the rat.

The effect of administration of lead in the maternal drinking water from conception to weaning on enkephalin levels in the developing rat striatum was studied between 10 and 100 days after birth. Concentrations of 300 and 1000 ppm Pb produced no overt toxicity in terms of effects on body and brain weight. However, marked differences in striatal enkephalins were observed. In lead-dosed animals enkephalin content was up to 50% lower at 10 and 21 days postpartum, and in addition lead appeared to delay the attainment of adult levels of this opioid neurotransmitter. Measures at later time points indicated that the effects of lead on enkephalin are reversible. The results suggest that lead depresses and delays the ontogeny of the enkephalinergic system within the striatum.