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Long-term analgesic reaction in attacked mice.
B Siegfried1, H R Frischknecht, G Riggio
1Institute of Pharmacology, University of Zurich, Switzerland.
Behavioral Neuroscience
|December 1, 1987
Summary
Stress-induced long-term analgesia (LTA) in mice can be reinstated 24 hours after an initial attack. Opioid system activation is necessary but not sufficient for this analgesic response.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Pain Research
Background:
- Stress-induced analgesia is a complex physiological response.
- Understanding the mechanisms of long-term analgesic (LTA) reactions is crucial for pain management.
- Previous research suggests a role for opioid systems in stress-induced analgesia.
Purpose of the Study:
- To characterize the long-term analgesic (LTA) reaction in mice subjected to attack stress.
- To investigate the temporal dynamics and opioid involvement in LTA.
- To determine if opioid system activation is sufficient for LTA.
Main Methods:
- Mice were subjected to varying levels of attack stress.
- Long-term analgesic responses were measured 24 hours after initial stress.
- Opioid antagonists (naloxone, beta-chlornaltrexamine) were administered.
- Morphine was used to substitute for attack stress.
Main Results:
- LTA was reinstated upon reexposure to a mild stressor 24 hours after initial attack.
- Opioid antagonists blocked LTA when given before reexposure, but not immediately after.
- Morphine administration did not induce LTA.
- LTA magnitude depended on the initial stress level.
Conclusions:
- Pain inhibitory mechanisms remain primed for at least 24 hours post-stress.
- Opioid system activation is necessary but not sufficient for LTA.
- LTA is only partially sensitive to opioid antagonists, suggesting involvement of other systems.