Dichloroacetate reduces sympathetic nerve responses to static exercise

Lactic acid is thought to be a stimulant of muscle metaboreceptors. The goal of the present study was to determine if inhibition of lactic acid production by dichloroacetate (DCA) would attenuate muscle sympathetic nerve activity (MSNA) during static forearm exercise. DCA increases pyruvate dehydrogenase levels. Thus, for a given amount of pyruvate produced, less lactic acid is formed. Seven subjects performed static forearm exercise at 20% maximal voluntary contraction until fatigue followed by posthand-grip circulatory arrest (PHG-CA) (trial 1). Subjects then received DCA (35 mg/kg) and repeated the exercise protocol (trial 2). We observed an attenuated rise in forearm venous lactate and MSNA. The trial 2 MSNA value during PHG-CA was 51 ± 11% less than the value during trial 1 (P < 0.01). In seven control subjects, two bouts of static forearm exercise were performed with an intervening saline infusion. This intervention had no effect on lactate or MSNA responses to exercise. We conclude that DCA attenuates lactate responses to static exercise, and this is associated with a blunted MSNA response.