Morphine tolerance after chronic intracerebroventricular injection in male and female mice.
We compared morphine analgesia ED(50) values of male and female mice prior to (Day 1) and after (Day 4) 3 days of intracerebroventricular morphine injections. Increases in ED(50) values from Day 1 to Day 4, indicating tolerance, were of similar magnitude in both sexes. The data suggest that spinal opioid analgesic mechanisms, acting alone or in synergy with supraspinal loci, may contribute to pharmacodynamic explanations of sex differences in systemic morphine tolerance.
Kest
B
B
Department of Psychology and Center for Developmental Neuroscience, (4S-223), The College of Staten Island/City University of New York, 2800 Victory Blvd., Staten Island, New York, NY 10314, USA. kest@postbox.csi.cuny.edu
Hopkins
E
E
D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D005260:Female; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D012727:Sex Characteristics; D013997:Time Factors
D000701:Analgesics, Opioid; D009020:Morphine