Acetaldehyde-induced changes in the monoamine and amino acid extracellular microdialysate content of the nucleus accumbens

The effect of an acute intraperitoneal (i.p.) injection of acetaldehyde, 20 mg/kg or 100 mg/kg, on the microdialysate content of both amino acids and monoamines was studied in the nucleus accumbens (NA) by a microdialysis technique. Acetaldehyde, ACH, which was detectable at levels of 50-130 μmol/g brain tissue 10 min after injection, evoked a significant decrease in the extracellular microdialysis dopamine content, which was sustained for the period of the study, i.e. 120 min. Homovanillic acid, HVA, decreased significantly when the lower dose of ACH was administered while dihydrophenylacetic acid, DOPAC, showed no significant change with either dose of ACH during the period of the study. Serotonin levels decreased significantly after both doses of acetaldehyde, with significant increases of its major metabolite, hydroxyindolacetic acid, 5-HIAA, with the higher acetaldehyde dose. Taurine increased significantly, only during the first twenty minutes, after both doses of acetaldehyde, although neither of the excitatory amino acids assayed, glutamate and aspartate, nor the inhibitory amino acid, GABA, showed any significant changes. Acetaldehyde clearly evokes significant perturbation in the monoamine content of the NA, such changes being the converse to those reported for monoamines after ethanol administration, which might indicate a negative reinforcement effect.