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Hypergravity and opioid-mediated pain suppression in rats.
Y Kumei1, R Shimokawa, M Terasawa
1Section of BioMatrix, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
Journal of Gravitational Physiology : a Journal of the International Society for Gravitational Physiology
|March 26, 2003
Summary
Exposure to 2 G hypergravity elevates pain thresholds in rats, suggesting a role for the body's natural pain-relief system. This effect may involve beta-endorphins and can be blocked by naloxone.
Area of Science:
- Neuroscience
- Gravitational Biology
- Pain Research
Background:
- Environmental stimuli can suppress pain in animals.
- The impact of altered gravity on pain perception is not well understood.
- Fos protein expression in brainstem regions is linked to hypergravity exposure.
Purpose of the Study:
- To investigate the effects of hypergravity on nociceptive responses in rats.
- To explore the involvement of beta-endorphin in hypergravity-induced analgesia.
- To examine the counteraction of these effects by naloxone.
Main Methods:
- Exposure of rats to 2 G hypergravity (long-term and short-term).
- Measurement of nociceptive threshold on rat skin surfaces.
- Assessment of Fos protein induction in hypothalamic regions (arcuate nucleus, paraventricular nucleus).
- Administration of naloxone to test for opioid receptor involvement.
Main Results:
- Both long-term and short-term 2 G hypergravity exposure elevated the nociceptive threshold in rats.
- Fos protein was induced in the hypothalamus, including the arcuate and paraventricular nuclei.
- The analgesic effects of hypergravity were counteracted by naloxone, indicating opioid involvement.
Conclusions:
- Hypergravity exposure induces analgesia in rats by elevating the nociceptive threshold.
- Beta-endorphin, an endogenous opioid, is likely involved in this analgesic effect.
- Naloxone, an opioid receptor antagonist, can block the pain-suppressing effects of hypergravity.