Enhanced Acquisition of Cocaine Self-Administration in Adult Rats With Neonatal Isolation Stress Experience

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Examined the acquisition of self-administered cocaine addiction in adult male rats with neonatal isolation stress experience. Some Ss underwent neonatal isolation for 1 hr daily on postnatal days 2–9. At approximately 100 days of age, 4 escalating cocaine doses were administered for 5 days each, continuing with the highest dose until acquisition occurred. Results indicate that isolated Ss acquired operant conditioning for cocaine in fewer days and at lower doses than did non-isolated Ss. No differences between the 2 groups were observed in locomotor activity, acquisition of operant responding for food, or in number of days to extinguish self-administration. Findings suggest that neonatal isolation stress increases rats' vulnerability to cocaine addiction; findings have important implications for the role of early childhood stress in human vulnerability to cocaine addiction.