Acute withdrawal after repeated ethanol treatment reduces the number of spontaneously active dopaminergic neurons in the ventral tegmental area

The effect of acute withdrawal, after repeated ethanol administration, on the electrophysiological activity of dopamine (DA) neurons in the ventral tegmental area was studied. Male rats received a 10-day treatment of ethanol at 4 g/kg, twice daily via intragastric intubation. In animals treated with ethanol, the number of spontaneously active DA neurons, determined with the cells-per-track population sampling technique, was significantly reduced (ethanol group = 0.70±0.10; control group = 1.49±0.18). I.V. apomorphine (20-64 μg/kg) reversed the reduced number of spontaneously active DA neurons (1.30±0.14) to near control levels. 'Silent' DA neurons could also be induced to fire by microiontophoretic application of GABA. These results suggest that the reduction in the number of spontaneously active DA neurons was due to the induction of tonic depolarization-inactivation on these neurons.