Abstract
We previously reported that chronic exposure of male rats to morphine markedly increases the concentration of corticosteroid-binding globulin (CBG) in blood. This in turn appears to greatly reduce the amount of corticosterone available to intracellular receptors. In the study reported here, we found that in contrast to the effect in males, morphine has no apparent effect on CBG in females. This pronounced sex difference does not appear to be attributable to differences in morphine pharmacokinetics, short-term actions of gonadal hormones in adulthood or sex differences in CBG or corticosterone levels. In any case, it is evident that morphine does not decrease the level of physiologically active corticosterone through CBG in females as it appears to do in males. On the other hand, we also found a distinct sex difference with regard to the effects of morphine on corticosterone. Chronic exposure to morphine had no apparent effect on corticosterone levels in males but resulted in markedly lower levels in females. Thus, morphine appears to cause a deficit in physiologically active corticosterone in both sexes but by different mechanisms.
Footnotes
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Send reprint requests to: Bruce Nock, Ph.D., Washington University School of Medicine, Department of Psychiatry, 4940 Children’s Place, St. Louis, MO 63110. E-mail: bruce{at}dcm.wustl.edu
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↵1 This research was supported in part by USPHS Grants DA09344 (Bruce Nock), DA03833 (Theodore J. Cicero) and DA09140 (Theodore J. Cicero) from the National Institute on Drug Abuse.
- Abbreviations:
- ACTH
- adrenocorticotropic hormone
- ADX
- adrenalectomy
- CAST
- castration
- CBG
- corticosteroid-binding globulin
- HIV
- human immunodeficiency virus
- OVX
- ovariectomy
- RIA
- radioimmunoassay
- Received June 16, 1997.
- Accepted April 20, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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