The effect of gut microbiome on tolerance to morphine mediated antinociception in mice

Area of Science:

• Microbiology
• Neuroscience
• Pharmacology

Background:

• Gastrointestinal microbiota play crucial roles in physiology and disease.
• Chronic morphine use, a common pain therapy, alters gut bacteria and can lead to translocation.
• The impact of gut bacteria on morphine's effects, particularly tolerance, requires further investigation.

Purpose of the Study:

• To investigate the role of the gastrointestinal microbiome in the development of antinociceptive tolerance to chronic morphine.
• To determine if modulating gut bacteria affects morphine-induced gut pathology and neuronal hypoexcitability.

Main Methods:

• Mice were treated with an antibiotic cocktail (ABX) to deplete gut bacteria.
• Pharmacodynamic effects of chronic morphine, including antinociception, gut permeability, and colonic inflammation, were assessed.
• Primary afferent neurons from dorsal root ganglia (DRG) were used to evaluate morphine-induced hypoexcitability in vitro.

Main Results:

• Antibiotic treatment prevented chronic morphine-induced increases in gut permeability, colonic mucosal destruction, and IL-1β expression.
• Antibiotic treatment blocked the development of antinociceptive tolerance to morphine in behavioral assays.
• Antibiotic treatment prevented tolerance to morphine-induced hypoexcitability in isolated DRG neurons.
• Antibiotic treatment did not affect naloxone-precipitated withdrawal.

Conclusions:

• The gastrointestinal microbiome is a key modulator of physiological responses to chronic morphine.
• Targeting the gut microbiome may represent a novel strategy to manage pain and mitigate side effects of chronic opioid therapy.
• Gut bacteria are essential for the development of morphine tolerance but not for acute withdrawal symptoms.