The effect of glucose on antipsychotic drug-induced changes in the spontaneous activity of rat midbrain dopaminergic neurons was tested with the cells-per-track extracellular electrophysiology method. After daily s.c. treatment with vehicle, haloperidol (0.5 mg/kg), or clozapine (20 mg/kg) for 21 days, rats were anesthetized and recordings performed on one side of the brain. Then. glucose (250 mg/kg, i.v.) was administered and recordings were made from the contralateral midbrain. Glucose significantly reduced the number of spontaneously active A9 and A10 dopaminergic cells per track in control rats, but significantly attenuated the chronic haloperidol- and clozapine- induced reductions in dopaminergic cells per track. These results suggest that caloric intake may influence antipsychotic drug-induced changes in the population activity of midbrain dopaminergic neurons. (C) 2001 Elsevier Science B.V. All rights reserved.