Journal article
Morphine antagonizes U50,488's effects in a squirrel monkey shock titration procedure
European journal of pharmacology, Vol.234(2), pp.199-207
1993
Handle:
https://hdl.handle.net/2376/106456
PMID: 8387010
Abstract
To determine whether a μ opioid agonist modulates the effects of a κ opioid agonist in squirrel monkeys responding under a shock titration procedure, morphine was administered in combination with an ED
75 dose of U50,488. Morphine (0.03–0.3 mg/kg) did not alter U50,488's early peak effects (15–25 min post-injection), but dose dependently antagonized U50,488's later effects (40–100 min post-injection); these doses of morphine shifted the U50,488 dose-effect curve
<
1
4
log
unit to the right. After 6–8 weeks of daily morphine administration, higher doses of morphine (0.3–3.0 mg/kg) shifted the U50,488 dose-effect curve
>
1
2
log
unit to the right. Morphine still did not antagonize early peak effects of the ED
75 dose of U50,488, but antagonized early and late effects of a lower dose. Thus, morphine is a weak κ antagonist in the shock titration procedure. In addition to its low affinity for κ receptors, morphine's κ antagonist activity is limited by its μ agonist effects, particularly in the non-morphine-tolerant monkey.
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Details
- Title
- Morphine antagonizes U50,488's effects in a squirrel monkey shock titration procedure
- Creators
- Rebecca M CraftLinda A Dykstra
- Publication Details
- European journal of pharmacology, Vol.234(2), pp.199-207
- Academic Unit
- Psychology, Department of
- Publisher
- Elsevier B.V
- Identifiers
- 99900546715201842
- Language
- English
- Resource Type
- Journal article