Pretreatment of mice with a single injection of morphine or by chronic implantation of morphine pellets increased the ability of naloxone to antagonize the antagonize the analgetic effects of morphine. However, this increased effectiveness of naloxone was also produced by pretreatment with diethylether, ACTH, corticosterone or dexamethasone. Thus, the increased potency of naloxones observed after pretreatment witn narcotics may be due, at least in part, to those pretreatments on the pituitary-adrenal axis. In addition, in animals made highly tolerant and dependent by cAMP administration during morphine pellet implantation, the narcotic antagonist potency of naloxones was similar to that of untreated animals.
Bibliographical noteFunding Information:
This research was supported by Grants DA-00037 and DA-00564 and by a NIDA Postdoctoral Fellow- ship (DA-02785) to R.A. Harris. The authors would like to thank Ms. Barbara Hitzemann and Ms. Cindy O'Toole for their fine technical assistance.
Copyright 2014 Elsevier B.V., All rights reserved.
- Cyclic AMP
- Morphine analgesia
- Narcotic tolerance