The effects of repeated corticosterone exposure on the interoceptive effects of alcohol in rats.
OBJECTIVE
Repeated and/or heightened elevations in glucocorticoids (e.g., repeated stress) can promote escalated drug-taking behaviors and induce compromised HPA axis function. Given that interoceptive/subjective drug cues are a fundamental factor in drug-taking behavior, we sought to determine the effects of exposure to repeated elevations in the glucocorticoid corticosterone (CORT) on the interoceptive effects of alcohol in rats using drug discrimination techniques.


METHODS
Male Long Evans rats trained to discriminate alcohol (1 g/kg, IG) vs. water were exposed to CORT (300 μg/ml) in the home cage drinking water for 7 days. The interoceptive effects of experimenter- and self-administered alcohol were assessed and HPA axis function was determined.


RESULTS
The interoceptive effects of experimenter- and self-administered alcohol were blunted following CORT. Control experiments determined that this decreased sensitivity was unrelated to discrimination performance impairments or decreased CORT levels at the time of testing and was dependent on repeated CORT exposure. Susceptibility to compromised HPA axis function following CORT exposure was suggested by an altered pattern of CORT secretion and blunted CORT response following injection of the synthetic glucocorticoid dexamethasone.


CONCLUSIONS
These findings present a possible behavioral mechanism for escalated alcohol drinking during episodes of heightened elevations in glucocorticoids (e.g., stress). That is, during these episodes, individuals may consume more alcohol to achieve the desired interoceptive effects. Understanding these behavioral mechanisms may lead to a better understanding of factors that promote alcoholism and alcohol abuse in at risk populations.
Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Thurston-Bowles Building, CB#7178, Chapel Hill, NC 27599, USA. jbesheer@med.unc.edu
Joyce
J
Besheer
Kristen R
KR
Fisher
Julie J M
JJ
Grondin
Reginald
R
Cannady
Clyde W
CW
Hodge
D000818:Animals; D003345:Corticosterone / Q000008:administration & dosage* / Q000633:toxicity; D004193:Discrimination Learning / Q000187:drug effects* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000008:administration & dosage*; D008297:Male; D051381:Rats; D020318:Rats, Long-Evans; D012646:Self Administration; D013315:Stress, Psychological / Q000139:chemically induced / Q000523:psychology
D000431:Ethanol; D003345:Corticosterone