Long-term development of excessive and inflexible nicotine taking by rats, effects of a novel treatment approach.

Rationale: Addiction is characterized by inflexible drug consumption: unpleasant consequences are accepted. Rat studies with several drugs proved that long-term voluntary intake induced abstinence-outlasting excessive and inflexible consumption.

Objective: Establishing a long-term model of oral self-administration of nicotine in rats with outlasting consequences for flexibility; testing a novel approach to restore flexibility by increasing neuroplasticity for memory reorganization via glucocorticoids.

Long-term voluntary D-amphetamine consumption and behavioral predictors for subsequent D-amphetamine addiction in rats.

Flexibility of drug taking is characteristic for "controlled" drug consumption whereas addiction is reflected by inflexibility and persistent high risk to relapse. Male Wistar rats (N = 12) that were given a continuous free choice between water and D-amphetamine solutions for 16 weeks, revealed a moderate and flexible pattern of D-amphetamine intake when tested again after 36 weeks of drug deprivation. A second group of rats had the same choice between water and D-amphetamine for 42 weeks.