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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
Exercise-induced morphine insensitivity is accompanied with a decrease in specific G-protein subunits gene expression
Saeed Esmaeili-Mahani1, Zahra Ebrahimi, Tahmores Noraie
1Laboratory of Molecular Neuroscience, Kerman Neuroscience Research Center (KNRC), Kerman University of Medical Sciences, Kerman, Iran. semahani@yahoo.com
Pharmacology, Biochemistry, and Behavior
|February 23, 2013
Summary
Physical training reduces the pain-relieving effects of morphine in rats. This exercise-induced morphine insensitivity is linked to decreased levels of G-protein subunits (Gαi and Gβ) in the spinal cord.
Area of Science:
- Neuroscience
- Pharmacology
- Exercise Physiology
Background:
- Morphine's analgesic potency is reduced in animals that have undergone exercise training.
- G-protein subunits play a crucial role in mediating opioid effects at the cellular level.
- The precise mechanisms underlying exercise-induced morphine insensitivity remain unclear.
Purpose of the Study:
- To investigate the changes in Gαi and Gβ protein gene expression in response to exercise training.
- To elucidate the molecular mechanisms contributing to exercise-induced morphine insensitivity.
Main Methods:
- Male Wistar rats were subjected to treadmill exercise.
- Nociceptive thermal threshold was measured using the tail-flick test.
- Semiquantitative RT-PCR and Western blot were used to quantify Gαi and Gβ mRNA and protein levels in the dorsal spinal cord.
Main Results:
- Exercise-trained rats exhibited significantly suppressed antinociceptive responses to intrathecal morphine.
- Physical training led to a significant decrease in both mRNA and protein levels of Gαi and Gβ in the lumbar spinal cord.
- These changes were statistically significant (P<0.001 for Gαi mRNA, P<0.05 for Gαi protein, P<0.01 for Gβ mRNA, P<0.001 for Gβ protein).
Conclusions:
- Exercise training alters the expression of opioid receptor signaling elements in the spinal cord.
- Reduced expression of Gαi and Gβ proteins may be a key factor in exercise-induced morphine insensitivity.
- These findings provide insights into the neurobiological adaptations underlying altered opioid response to exercise.
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