RATIONALE: Developmental lead exposure has been found to produce differential patterns of drug self-administration in adult animals. OBJECTIVES: The present study examined the effects of perinatal (gestation/lactation) lead exposure on adult patterns of heroin self-administration. METHODS: Female rats were gavaged daily with 0 mg or 16 mg lead for 30 days prior to breeding with non-exposed males. Metal administration continued through pregnancy and lactation and was discontinued at weaning [postnatal day 21 (PND 21)]. Animals born to control or lead-exposed dams received indwelling jugular catheters as adults and were randomly assigned to one of two studies. In experiment 1, animals were tested on a FR-2 schedule in an effort to examine differential sensitivity to heroin in an intravenous self-administration paradigm. Seven doses of heroin were selected ranging from 0.56 microg/kg to 36 microg/kg per infusion. In experiment 2, littermates were tested on a progressive ratio (PR) schedule in order to more explicitly determine the nature of the change in sensitivity to the drug. RESULTS: In experiment 1, lead-exposed animals responded for heroin at significantly lower rates across most doses as evidenced by a downward shift in the inverted-U dose-effect curve. Congruent with these findings, lead-exposed animals in experiment 2 exhibited a decrease in progressive ratio responding (lower breaking points) across all heroin doses, further suggesting that perinatal lead exposure attenuates opiate self-administration in adult animals by altering the rewarding efficacy of the drug. In experiment 2, it was determined further that lead-exposed animals had lower latencies to make the initial lever press for heroin. CONCLUSIONS: These results support previous literature suggesting that perinatal exposure to inorganic lead attenuates the effectiveness of opiates as a reinforcer when animals are tested in the adult life cycle.
RATIONALE: Developmental lead exposure has been found to produce differential patterns of drug self-administration in adult animals. OBJECTIVES: The present study examined the effects of perinatal (gestation/lactation) lead exposure on adult patterns of heroin self-administration. METHODS: Female rats were gavaged daily with 0 mg or 16 mg lead for 30 days prior to breeding with non-exposed males. Metal administration continued through pregnancy and lactation and was discontinued at weaning [postnatal day 21 (PND 21)]. Animals born to control or lead-exposed dams received indwelling jugular catheters as adults and were randomly assigned to one of two studies. In experiment 1, animals were tested on a FR-2 schedule in an effort to examine differential sensitivity to heroin in an intravenous self-administration paradigm. Seven doses of heroin were selected ranging from 0.56 microg/kg to 36 microg/kg per infusion. In experiment 2, littermates were tested on a progressive ratio (PR) schedule in order to more explicitly determine the nature of the change in sensitivity to the drug. RESULTS: In experiment 1, lead-exposed animals responded for heroin at significantly lower rates across most doses as evidenced by a downward shift in the inverted-U dose-effect curve. Congruent with these findings, lead-exposed animals in experiment 2 exhibited a decrease in progressive ratio responding (lower breaking points) across all heroin doses, further suggesting that perinatal lead exposure attenuates opiate self-administration in adult animals by altering the rewarding efficacy of the drug. In experiment 2, it was determined further that lead-exposed animals had lower latencies to make the initial lever press for heroin. CONCLUSIONS: These results support previous literature suggesting that perinatal exposure to inorganic lead attenuates the effectiveness of opiates as a reinforcer when animals are tested in the adult life cycle.
Authors: Jack R Nation; Aaron L Cardon; Heather M Heard; Rodrigo Valles; Gerald R Bratton Journal: Psychopharmacology (Berl) Date: 2003-03-25 Impact factor: 4.530
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