Metabolomic profiling of cocaine plus ethanol poly-consumption in young adult rats: Insights into the incubation of drug seeking.

The combined use of cocaine and alcohol is highly prevalent and produces more severe effects than either drug alone. This study investigates this polysubstance abuse pattern by modelling the incubation of cocaine craving, both alone and in combination with ethanol. To investigate the mechanisms underlying this phenomenon, we performed an untargeted plasma metabolomic analysis using High-Performance Liquid Chromatography coupled with a High-Resolution Hybrid Quadrupole-Orbitrap mass spectrometer. Both positive and negative ionization modes, and two complementary chromatographic methods, were employed to maximize compound detection. We analysed metabolite differences after 30 versus 2 days of withdrawal in rats that self-administered cocaine alone or with ethanol and then, identified the pathways in which these metabolites are involved to reveal the biological processes that could be affected during craving incubation. Although all rats were exposed to cocaine, those that also consumed ethanol showed distinct metabolic pathway alterations. Both sexes exhibited changes in similar pathways, yet the specific metabolites affected differed, revealing clear sex dimorphism. Cocaine primarily altered tryptophan metabolism and the urea cycle, whereas the combination with ethanol mainly affected α-linolenic acid metabolism, bile acid synthesis, and arginine, proline, glycine, serine, and threonine metabolism. This study provides insight into peripheral metabolomic alterations during the incubation of cocaine and cocaine plus ethanol seeking, offering a framework for further investigation of the affected pathways in peripheral tissues and within the central nervous system in both sexes.