Feeding enhances extracellular lactate of local origin in the rostromedialhypothalamus but not in the cerebellum

The use of brain microdialysis together with chronic vascular catheterizati on allowed us to assay extracellular fluid lactate (ECFL) in both the ventr omedial-paraventricular (VMH-PVN) area of the hypothalamus and the cerebell um, in parallel with measures of plasma levels, and in relation to food int ake. A 45 min scheduled meal increased VMH-PVN ECFL by 28%. This increase w as not observed in the cerebellum. The prandial increase in plasma glucose (43%, from 4.74 to 6.77 mM) and lactate (84%, from 0.83 to 1.53 mM) showed a different temporal pattern and lasted longer than that of the ECFL. Gluco se delivery by reverse dialysis for 45 min into the VMH-PVN area increased ECFL by 49%. When local glucose utilization was prevented by reverse dialys is-delivered 2-deoxy-D-glucose (2-DG), not only did VMH-PVN ECFL drop, but the feed-related increase in ECFL was blocked without affecting the normal rise in plasma glucose and in lactate. These results indicate that meal-rel ated ECFL production and variations are independent of circulating lactate, but may depend on substrate availability in these hypothalamic structures. (C) 1999 Elsevier Science B.V. All rights reserved.