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Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
THE ACTION OF DRUGS ON RESPIRATION : I. THE MORPHINE SERIES
1Laboratory of Pharmacology of the University of Pennsylvania, Philadelphia.
The Journal of Experimental Medicine
|October 30, 2009
Summary
Morphine and heroine selectively depress active expiration in cats by slowing lung emptying. This respiratory depression is linked to circulatory failure at higher doses, not the reverse.
Area of Science:
- Pharmacology
- Respiratory Physiology
Background:
- Understanding drug effects on respiratory mechanisms is crucial for clinical applications.
- The role of active expiration in drug-induced respiratory changes requires further elucidation.
Purpose of the Study:
- To investigate the effects of morphine, heroine, and codeine on respiratory control in cats.
- To differentiate the impact of these drugs on active versus passive expiration.
Main Methods:
- A novel method for recording intrathoracic pressure in intact cats was employed.
- Active expiration was stimulated using a carbon dioxide (CO2)-air mixture.
- The influence of morphine, heroine, and codeine on respiratory rate and depth was assessed.
Main Results:
- Morphine and heroine selectively depressed the central expiratory mechanism, leading to slower lung emptying.
- Codeine did not depress respiration in decerebrated cats.
- Respiratory depression from higher doses of morphine/heroine was associated with circulatory failure.
Conclusions:
- The primary respiratory effect of morphine and heroine in cats is the depression of active expiration.
- Spinal cord stimulation and active expiration were observed with morphine and codeine in decerebrated animals.
- Circulatory depression, not respiratory depression, appears to be the cause of death at high doses.
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