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Morphine conditioned place preference is attenuated by perinatal lead exposure
Rodrigo Valles1, Aaron L Cardon, Heather M Heard
1Department of Psychology, Texas A&M University, College Station, TX 77843, USA.
Pharmacology, Biochemistry, and Behavior
|July 23, 2003
Summary
Perinatal lead exposure in rats reduced the reinforcing effects of morphine in adulthood. Despite lead clearing from blood, brain lead levels remained elevated, suggesting lasting impacts on opioid response.
Area of Science:
- Neuroscience
- Toxicology
- Pharmacology
Background:
- Perinatal exposure to environmental toxins can have long-lasting effects on neurodevelopment and behavior.
- Lead is a known neurotoxin with potential to affect neurotransmitter systems, including opioid pathways.
Purpose of the Study:
- To investigate the impact of perinatal lead exposure on the conditioned reinforcing effects of morphine in adult offspring.
- To determine if early lead exposure alters the response to morphine later in life.
Main Methods:
- Dams were exposed to lead acetate (16 mg/kg/day) or a control solution from prior to breeding through lactation.
- Offspring were tested as adults (postnatal day 70) using a conditioned place preference (CPP) paradigm with varying doses of morphine.
- Blood and brain lead concentrations were analyzed post-testing.
Main Results:
- Lead-exposed offspring showed an attenuated conditioned place preference response to morphine at doses of 1.25 and 2.50 mg/kg compared to controls.
- Blood lead levels in exposed animals returned to control levels by the end of the testing period.
- Brain lead residues remained elevated in lead-exposed animals even after blood lead levels normalized, indicating persistent neurotoxicity.
Conclusions:
- Perinatal lead exposure can enduringly alter the conditioned reinforcing properties of morphine.
- Persistent lead accumulation in the brain, even after clearance from blood, may underlie the observed changes in opioid response.
- These findings highlight the critical vulnerability of the developing brain to lead toxicity and its potential long-term consequences on reward pathways.