Understanding morphine influence on gut health and depression: Evidence from a rat model

Opioid addiction severely impacts mental health, and recent evidence links opioid use to gut microbiota changes and mood disorders. This study examines how morphine influences gut microbiota, inflammatory responses, and depressive behaviors in rats.

Male Wistar rats received escalating morphine sulfate doses (30 mg/kg) or served as controls. Depressive-like behaviors were assessed via the Forced Swim Test (FST) and Sucrose Preference Test (SPT). Gut microbiota composition was analyzed using qPCR, and pro-inflammatory markers were measured in intestinal tissue.

Morphine treatment induced depressive-like behaviors, as evidenced by increased immobility time in the FST (120 s vs. 69.5 s in controls; P<0.01) and reduced sucrose preference (40%vs. 70% in controls; P<0.05). Gut microbiota analysis revealed a significant decrease in beneficial bacteria, including Bifidobacterium longum (P<0.05) and Lactobacillus rhamnosus (P=0.02), and an increase in pathogenic bacteria such as Fusobacterium nucleatum (P<0.001) and Clostridium difficile (P<0.01). Enterococcus faecalis was also significantly increased in the morphine-treated group (P<0.001). Ileal inflammatory marker analysis showed significantly elevated TNF-α (2.15±0.45, P<0.001) and IL-1β (3.81±1.16, P<0.001) mRNA levels, with a trend towards elevated IL-6 (1.72±1.75; P=0.22).

Morphine treatment significantly alters gut microbiota composition, worsening depressive-like behaviors and inducing intestinal inflammation. These findings highlight the complex link between opioid use, gut health, and mental well-being, suggesting microbiota-targeted therapies may help manage opioid addiction and related psychological disorders. Further research is needed to explore how modulating gut microbiota can lessen the negative effects of opioid therapy.