JPET

Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Full Text (PDF)
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Yeung, J. C.
Right arrow Articles by Rudy, T. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Yeung, J. C.
Right arrow Articles by Rudy, T. A.

Sites of antinociceptive action of systemically injected morphine: involvement of supraspinal loci as revealed by intracerebroventricular injection of naloxone

JC Yeung and TA Rudy

Dose-response lines for the tail-flick and hot plate tests were obtained in rats which had received systemic injections of morphine (10- 150 mg/kg i.p.) and intracerebroventricular (i.v.t.) injections of naloxone (3-20 micrograms). Diffusion studies indicated that the antagonist remained localized within supraspinal structures. Between the doses of 3 and 10 micrograms i.v.t. naloxone produced a dose- dependent rightward shifting of the morphine dose-response lines, the shift produced by the 10-micrograms dose being sufficient to abolish the analgetic action of morphine doses as large as 75 mg/kg. Higher doses of naloxone (e.g., 20 micrograms) produced no additional rightward shift, indicating an inability of i.v.t. naloxone to antagonize the analgesia produced by high systemic doses of morphine. These findings seem to suggest that analgesia produced by low to moderate systemic doses of morphine is mediated entirely by an action of the narcotic upon supraspinal structures. However, the results of an analogous study in which naloxone was injected into the spinal subarachnoid space indicated that analgesia produced by morphine given systemically in low to moderate doses is mediated exclusively by an action on the spinal cord. This apparent paradox can be resolved if one assumes that the total analgesia observed after a low to moderate systemic dose of morphine is a result of a multiplicative, rather than an additive, interaction of narcotic agonisms expressed at the spinal and supraspinal sites of action, respectively.

Volume 215, Issue 3, pp. 626-632, 12/01/1980
Copyright © 1980 by American Society for Pharmacology and Experimental Therapeutics




This article has been cited by other articles:


Home page
 Anesth. Analg.Home page
L. E. Mather and M. J. Cousins
The Site of Action of Epidural Fentanyl: What Can Be Learned by Studying the Difference Between Infusion and Bolus Administration? The Importance of History, One Hopes
Anesth. Analg., November 1, 2003; 97(5): 1211 - 1213.
[Full Text] [PDF]

Home page
 J. Pharmacol. Exp. Ther.Home page
W. Masocha, G. Horvath, A. Agil, M. Ocana, E. Del Pozo, M. Szikszay, and J. M. Baeyens
Role of Na+,K+-ATPase in Morphine-Induced Antinociception
J. Pharmacol. Exp. Ther., September 1, 2003; 306(3): 1122 - 1128.
[Abstract] [Full Text] [PDF]

Home page
 CLIN PEDIATRHome page
J. D. Tobias, J. K. Deshpande, R. C. Wetzel, J. Facker, L. G. Maxwell, and M. Solca
Postoperative Analgesia: Use of Intrathecal Morphine in Children
Clinical Pediatrics, January 1, 1990; 29(1): 44 - 48.
[Abstract] [PDF]


Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
All ASPET Journals Molecular Pharmacology Pharmacological Reviews
Molecular Interventions Drug Metabolism and Disposition

Copyright © 1980 by the American Society for Pharmacology and Experimental Therapeutics.