Longitudinal Analysis of Rat Gut Microbiome Composition and Fecal Metabolism Markers Following Prolonged Morphine Exposure

This study investigated temporal group-level changes in gut microbiome composition and fecal metabolic markers in Wistar rats following a 10-day administration of morphine. Fecal samples were collected at predefined post-discontinuation time points and analyzed using 16S rRNA gene sequencing and GC×GC-TOF/MS-based metabolomics, with a focus on short-chain fatty acids (SCFAs). Morphine exposure was associated with transient alterations in gut microbiome structure at early post-treatment time points, including changes in alpha diversity and shifts in the relative abundance of major bacterial taxa. Unsupervised multivariate analysis of fecal metabolomic profiles revealed substantial inter-individual variability without persistent global separation between control and morphine-treated groups. Targeted analysis identified transient reductions in the relative signal intensities of selected SCFAs shortly after morphine withdrawal, while no significant differences were observed at later time points. These findings suggest that morphine-associated perturbations of the gut microbiome and fecal metabolome are predominantly time-dependent and tend to diminish during extended post-discontinuation phases.