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Hyperthermic effects of morphine: set point manipulation by a direct spinal action
British Journal of Pharmacology
|September 1, 1977
Summary
Intrathecal morphine causes a dose-dependent increase in rat body temperature, mediated by the spinal cord. This effect is reversed by naloxone, indicating a direct spinal action of morphine on thermoregulation.
Area of Science:
- Neuroscience
- Pharmacology
- Physiology
Background:
- Morphine is known to affect body temperature, but the precise mechanisms, particularly spinal cord involvement, require further elucidation.
- Understanding the central nervous system's role in morphine-induced thermoregulation is crucial for managing side effects and developing targeted therapies.
Purpose of the Study:
- To investigate the direct effects of intrathecal morphine administration on body temperature regulation in rats.
- To determine the role of the spinal cord in morphine-induced hyperthermia and its interaction with naloxone.
Main Methods:
- Chronic indwelling catheters were implanted in the lumbar spinal subarachnoid space of rats for drug administration.
- Morphine and naloxone were administered intrathecally and/or systemically to assess dose-dependent effects on body temperature.
- Environmental temperature was varied to assess the independence of morphine's effects.
Main Results:
- Intrathecal morphine induced a dose-dependent increase in body temperature, which was antagonized by naloxone.
- The hyperthermic response to morphine was independent of environmental temperature and associated with coordinated thermoregulatory responses.
- Systemic morphine also caused hyperthermia, partially reversed by intrathecal naloxone, and naloxone induced hypothermia in morphine-tolerant rats.
Conclusions:
- Morphine exerts a direct, pharmacologically specific effect on the spinal cord, altering the thermoregulatory set point in rats.
- These findings highlight the spinal cord as a key site for morphine's influence on body temperature regulation.
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