Chronic methamphetamine self-administration alters cognitive flexibility in male rats.

RATIONALE: Methamphetamine (meth) addiction is a chronically relapsing disorder that often produces persistent cognitive deficits. These include decreased cognitive flexibility, which may prevent meth addicts from altering their habitual drug abuse and leave them more susceptible to relapse. Multiple factors including low rates of compliance with research study participation and varied drug use patterns make the relationship between cognitive flexibility and relapse difficult to establish in clinical populations.
OBJECTIVES: Here, we combined an extended-access meth self-administration paradigm with an automated set-shifting task in rats to directly compare cognitive flexibility performance with meth-seeking behavior.
METHODS: Rats were pre-trained on an automated visual discrimination task, followed by 14 days of extended access (6 h/day) of meth or sucrose self-administration. They were then tested in the set-shifting task on strategy shift and reversal and subsequently assessed for cue-induced reinstatement of meth seeking.
RESULTS: Rats with a history of meth, but not sucrose, self-administration had selective deficits in reversal learning. Specifically, meth rats had an increase in the total number of errors and perseverative errors (corresponding to the old stimulus-reward association) following the reversal shift, which correlated with prior stable meth self-administration. However, no relationship was seen between errors during the reversal and cue-induced reinstatement.
CONCLUSION: The lack of association between meth-induced reversal deficits and cue-induced reinstatement to meth seeking indicates that these two domains may constitute independent pathologies of meth addiction.