title: The influence of early lead exposure on morphine reinforcement in the rat.
abstract: The effect of early lead burdens on morphine-seeking behavior was investigated in the albino rat. Several concentrations of lead acetate were administered to nursing mother starting at 0,7 or 14 days after birth, or provided directly to the pups in the drinking water after weaning, so that lead exposure was continous for 3 successive weeks in each group. The offspring were later tested for acquisition and maintenance of a goal-box preference based on morphine reinforcement. High lead burdens imposed before the second week of age resulted in a mild but significantly greater incidence of morphine-seeking responses, as well as retarded growth, compared with placebo-treated controls or animals treated at a later age. The data support the proposition that lead, introduced at a critical stage of development via the lactating mother, increases the potency of morphine reinforcement as a result of changes in cerebral dopaminergic activity. This effect may be mediated directly by the high lead burdens in the offspring, or indirectly by interfering with the mother's nursing capacity.
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight / Q000187:drug effects; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007854:Lead / Q000009:adverse effects / Q000494:pharmacology*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000209:etiology*; D011247:Pregnancy; D051381:Rats; D012054:Reinforcement, Psychology
chemical_list: D007854:Lead; D009020:Morphine