Abstract | RATIONALE: OBJECTIVES: The effects of mitragynine and the prototypical opioid agonist morphine were compared for their capacity to decrease operant responding for food delivery, and to increase response latency to a thermal stimulus. METHODS: Male and female Sprague-Dawley rats responded under a multiple cycle fixed ratio 10 schedule of food delivery and were tested on a hot plate (52 °C) immediately after each cycle. Morphine and mitragynine were administered alone, in combination with each other, and in combination with the opioid antagonist naltrexone. RESULTS:
Morphine and mitragynine dose-dependently decreased schedule-controlled responding; the ED50 values were 7.3 and 31.5 mg/kg, respectively. Both drugs increased thermal antinociception; the ED50 value for morphine was 18.3. Further, doses of naltrexone that antagonized morphine did not antagonize mitragynine. Mitragynine (17.8 mg/kg) did not alter the rate-decreasing or antinociceptive effects of morphine. CONCLUSIONS:
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Authors | Takato Hiranita, Francisco Leon, Jasmine S Felix, Luis F Restrepo, Morgan E Reeves, Anna E Pennington, Samuel Obeng, Bonnie A Avery, Christopher R McCurdy, Lance R McMahon, Jenny L Wilkerson |
Journal | Psychopharmacology
(Psychopharmacology (Berl))
Vol. 236
Issue 9
Pg. 2725-2734
(Sep 2019)
ISSN: 1432-2072 [Electronic] Germany |
PMID | 31098655
(Publication Type: Journal Article)
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Chemical References |
- Analgesics
- Analgesics, Opioid
- Narcotic Antagonists
- Receptors, Opioid, mu
- Secologanin Tryptamine Alkaloids
- Morphine
- mitragynine
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Topics |
- Analgesics
(pharmacology)
- Analgesics, Opioid
(pharmacology)
- Animals
- Discrimination Learning
(drug effects, physiology)
- Dose-Response Relationship, Drug
- Female
- Male
- Mitragyna
- Morphine
(pharmacology)
- Narcotic Antagonists
(pharmacology)
- Pain Measurement
(drug effects, methods)
- Rats
- Rats, Sprague-Dawley
- Receptors, Opioid, mu
(agonists)
- Secologanin Tryptamine Alkaloids
(pharmacology)
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