Is Acetaldehyde a substance of abuse? Evidence from a free-access, three-bottle choice paradigm

At present, neuroscience literature dealing with Acetaldehyde (ACD), ethanol first metabolite, as a drug of abuse, reported conditioned taste aversion paradigm and conditioned place preference, following ICV or i.p. administration. No reports exist on ACD oral self-administration probably because of its high volatility. For this reason, this pilot study was aimed at the evaluation of ACD concentration in aqueous solutions, and consequently to the rat drinking behaviour when acetaldehyde was presented in a free-access paradigm together with water and a sweet solution. Preliminarly we investigated the loss of ACD content in aqueous standard solutions. For the investigation of ACD concentration, all standard samples (ACD concentration ranging from 2 to 90 mM) were analysed in triplicate at regular time intervals (t = 0 h,12 h, 24 h and 48h.) using UV-Vis method at ? = 276 nm. Despite of ACD great volatility, no appreciable loss of ACD has been found in all solutions tested. When adult male Wistar rats were subjected to a three bottle choice paradigm with ACD 9mM, saccharin 0,125% (w/v) plus methyl-paraben 0,1% (w/v), and tap water, the amount of fluid intake was monitored every 24 h, and bottles were refilled every day with fresh solutions. Our results demonstrate that rats do self-administer ACD, even in the presence of a sweet solution and that their preference toward the ACD gradually increases day by day. In conclusion our pilot study shows for the first time that ACD concentration is maintained in an aqueous solution within 24 hours and that rats spontaneously self-administer ACD in a free-access paradigm even in the presence of a saccharin solution, providing further evidence of the addictive properties of ACD.