Dopamine D1 and D2 receptors regulate extracellular lactate and glucose concentrations in the nucleus accumbens.

Glucose and lactate have been shown to play a significant role in energy metabolism in the brain. In the present study, the relationship between extracellular glucose and lactate concentrations in the nucleus accumbens (NAC) was determined with in vivo microdialysis technique. We further evaluated the effect of dopamine (DA) receptor agonists on energy metabolism. Extracellular glucose levels were increased following inactivation of neurons by tetrodotoxin (TTX) perfusion, whereas neural activation by veratridine or K(+) perfusion decreased extracellular glucose concentrations. By contrast, lactate levels were increased by veratridine or K(+) perfusion, but were unaltered by TTX. Apomorphine (0.05 mg/kg), a mixed D1/D2 receptor agonist, did not alter the extracellular glucose and lactate concentrations, while a higher dose (0.5 mg/kg) increased them. Bromocriptine, a selective D2 receptor agonist, increased extracellular glucose, but not lactate concentrations. These results indicate that extracellular lactate levels may be a more suitable indicator of acute neural activation than glucose levels, and that simultaneous stimulation of D1 and D2 receptors enhances energy demands of DA neurons in the NAC.