Effect of ethanol on extracellular dopamine in rat striatum by direct perfusion with microdialysis

The concentration-related effects of ethanol on extracellular dopamine (DA) in rat striatum were studied by direct perfusion through microdialysis probes in freely moving rats. Two sets of three ethanol concentrations were separately tested using a Latin square experimental design. Potassium stimulation with high potassium (50 mM) in artificial CSF (ACSF) preceding ethanol treatment confirmed the neuronal function of dopaminergic cells by increasing DA concentrations to 200-1,500% of basal levels. The perfusion with calcium-free ACSF applied at the end of each experiment confirmed the calcium dependency of the basal levels of extracellular DA by decreasing basal DA levels by 70%. The striatal volume measurement to examine the possible brain damage by direct ethanol perfusion suggested that ethanol did not increase the damage caused by the probe implantation at any ethanol concentration tested in this study. The 30-min direct perfusion of 510 and 860 mM ethanol resulted in a significant concentration-related stimulatory effect on the extracellular DA concentration in rat striatum (510 mM, 29% increase, p < 0.05; 860 mM, 66% increase, p < 0.05). However, there was no significant effect of ethanol at low concentrations, < or = 170 mM. Considering the effective ethanol concentration in tissue areas in which DA is sampled, the data suggest that concentrations of ethanol associated with moderate intoxication do not directly affect the extracellular concentration of DA in the striatum. Therefore, the systemic effects of ethanol on striatal DA found in previous studies may be caused by the interaction with sites other than the striatum.