BACKGROUND
Individually, both treatment with progesterone and concurrent access to an
exercise wheel reduce cocaine self-administration under long-access conditions and
suppress cocaine-primed reinstatement in female rats. In the present study, wheel
running and progesterone (alone and combined) were assessed for their effects on
reinstatement of cocaine-seeking primed by yohimbine, cocaine, and cocaine-paired
cues.
METHODS
Male and female rats were implanted with an intravenous catheter and allowed to
self-administer cocaine (0.4 mg/kg/inf, iv) during 6-h sessions for 10 days.
Subsequently, the groups of male and female rats were each divided into 2 groups that
were given concurrent access to either a locked or unlocked running wheel under
extinction conditions for 14 days. Next, all 4 groups were tested in a within-subjects
design for reinstatement of cocaine-seeking precipitated by separate administration of
cocaine-paired stimuli, yohimbine, or cocaine; or the combination of yohimbine +
cocaine-paired stimuli or cocaine + cocaine-paired stimuli. These priming conditions
were tested in the presence of concurrent wheel access (W), pretreatment with
progesterone (P), or both (W+P).
RESULTS
In agreement with previous results, females responded more for cocaine than
males during maintenance. Additionally, concurrent wheel running attenuated extinction
responding and cocaine-primed reinstatement in females but not males. Across all priming
conditions, W+P reduced reinstatement compared to control conditions, and for
cocaine-primed reinstatement in male rats, the combined W+P treatment was more effective
than W or P alone.
CONCLUSION
Under certain conditions, combined behavioral (exercise) and pharmacological
(progesterone) interventions were more successful at reducing cocaine-seeking behavior
than either intervention alone.