Potentiation of cocaine-primed reinstatement of drug seeking in female rats during estrus.
BACKGROUND
Gender differences exist in the patterns of drug taking in cocaine addiction, suggesting that the propensity to relapse varies between men and women. Previous reports have shown sex differences in both cocaine-primed and conditioned-cued reinstatement of cocaine-seeking behavior, including recent evidence that the estrous cycle influences the level of conditioned-cued reinstatement. However, the influence of the estrous cycle on cocaine-primed reinstatement has not been examined.


OBJECTIVE
Accordingly, we assessed the influence of sex and estrous cycle status on cocaine-primed reinstatement of drug-seeking behavior in Sprague-Dawley rats.


METHODS
Intact male and female rats were trained to lever press to self-administer intravenous cocaine (0.5 mg/kg every infusion; fixed ratio 1, 20-s time-out following each infusion), followed by prolonged extinction training, and subsequently tested for the ability of a cocaine-priming injection (0, 5, or 10 mg/kg i.p.) to reinstate extinguished cocaine seeking (i.e., nonreinforced lever responding).


RESULTS
Despite no differences in cocaine intake between male and female rats, females responded more on the cocaine-paired lever during self-administration and extinction relative to males. Subsequently, both males and females exhibited a dose-dependent cocaine-primed reinstatement of extinguished drug-seeking behavior. Moreover, females in estrus exhibited significantly higher reinstatement than either males or non-estrus females, following a high-dose (10 mg/kg) cocaine prime.


CONCLUSIONS
Estrus females display heightened sensitivity to the motivational and/or stimulant effects of cocaine, suggesting that hormonal state modulates drug craving and propensity for drug relapse in cocaine addicts.
Department of Neuroscience, Medical University of South Carolina, Charleston, SC 29425, USA.
Tod E
TE
Kippin
Rita A
RA
Fuchs
Ritu H
RH
Mehta
Jordan M
JM
Case
Macon P
MP
Parker
Heather A
HA
Bimonte-Nelson
Ronald E
RE
See
D000818:Animals; D003042:Cocaine / Q000008:administration & dosage* / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D004971:Estrus; D005108:Extinction, Psychological / Q000187:drug effects; D005260:Female; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012008:Recurrence; D012646:Self Administration; D012727:Sex Characteristics
D003042:Cocaine