Habituation of lactate release responding to stressful stimuli in rat prefrontal cortex in vivo

The extracellular level of lactate is mainly dependent on functional glucose metabolism in most brain cells regulated in part by neuronal activity. We investigated the effect of environmental stimuli on lactate release in rat medial prefrontal cortex (MPFC) by in vivo brain microdialysis. Lactate release was clearly demonstrated to increase immediately and transiently from its steady-state levels after various stimuli (tail pinch for 1 min, 100-dB white noise for 5 min, and immobilization for 5 min). These stimuli-induced increments were depressed after a second trial 1 h later in a manner consistent with dishabituation to a novel stimulus and "below-zero" habituation by several repetition. Likewise the local perfusion of dopamine or norepinephrine transiently increased and then diminished the second perfusion-induced increase in MPFC lactate release consistent with desensitization. These results suggest the possibility that stressful stimuli produce one-trial habituation of lactate release in MPFC via a mechanism involving the regulation of the catecholaminergic system.