Low-speed uphill exercise increases lactate and brain-derived neurotrophic factor in brain regions for memory and learning

We investigated the acute effects of low-speed uphill exercise on lactate levels and brain-derived neurotrophic factor (BDNF) expression in the cortex and hippocampus. Male Sprague Dawley rats were divided into control, flat exercise (flat-EX), and uphill exercise (uphill-EX). EX groups were subjected to treadmill EX at a low speed of 13 m/min for 30 min or 90 min on 0 % (flat-EX) or 40 % (uphill-EX) grades. Lactate levels in the blood and brain increased in the uphill-EX but not in the flat-EX. Despite the slow speed, uphill-EX decreased muscle glycogen, with a predominance of fast-twitch fibers; however, brain glycogen remained unchanged in both EX-groups. Sodium lactate was administered via external jugular catheterization to determine whether the uphill EX-induced brain lactate increase was derived from blood. Changes in blood lactate levels coincided with those in the brain, indicating that an elevation in blood lactate may lead to increased brain lactate levels. Furthermore, although a longer uphill exercise of 90 min increased BDNF protein levels in the cortex and hippocampus, the flat-EX did not cause a change. These results suggest that prolonged low-speed uphill exercise, which recruits fast-twitch muscles, acutely increases lactate and BDNF in the brain regions for memory and learning.