Our new study is out now in the journal Neuropsychopharmacology. Here we examined the impact of opioids (morphine) on the community of symbiotic bacteria that reside in your gut (your gut microbiome). You can read more about this work in the recent news releases out in Nature Medicine and Pain Research Forum.

We found that morphine treatment significantly altered the abundance of certain bacteria in the gut. But, surprisingly, the effect on the gut microbiome was contingent on the regimen of morphine administration. Intermittent morphine (morphine injections spaced by repeated periods of withdrawal) had a completely different effect on the gut microbiome than sustained morphine (slow release morphine with no withdrawal periods). This suggests that opioid withdrawal – as well as opioids themselves – impact the gut microbiome, but do so in very distinct ways.

We went on to show that these changes in the gut microbiome are causally related to many of the symptoms of opioid dependence. We did this by treating control mice with a cocktail of oral antibiotics in order to deplete their own gut microbiome. We then recolonized their gut with fecal samples isolated from animals treated with intermittent

morphine. Recolonizing control mice with an “opioid” microbiome was sufficient to create cellular and behavioural changes that mimic an opioid dependent state. Control mice with an “opioid” gut microbiome exhibited inflammation in the brain and spinal cord, increased pain, and impairments in reward processing.

The results from this study are important because it suggests strategies that restore or manipulate the gut microbiome may be effective therapies for treating those suffering from opioid addiction. In particular, strategies to improve gut health during periods of opioid withdrawal may improve abstinence rates amongst those suffering from addiction.