Changes of blood lactate levels after repetitive transcranial magnetic stimulation, Neuroscience Letters 450 (2009) 111–113.

The objective was to study whether repetitive transcranial magnetic stimulation (rTMS) of the motor cortex could induce modification of peripheral blood lactate values. Nineteen young healthy volunteers were included; during the study, all subjectswere at rest, sitting on a comfortable armchair. The muscular activationwas evaluated by continuous electromyographic record. TMSwas performed by using a circular coil at the vertex. Resting motor threshold (rMT) was defined as the lowest TMS intensity able to induce motor responses of an amplitude >50 V in the relaxed contralateral target muscle in approximately 50% of 20 consecutive stimuli. Venous blood lactate values were measured before, immediately after and 10 min after a single session of low frequencies (1 Hz for 15 min) rTMS (LF rTMS) or high frequency (20 Hz for 15 min) rTMS (HF rTMS). As expected, LF rTMS induced a decrease of motor cortex excitability, whereas HF rTMS evoked an increase of motor cortex excitability. However, in the present investigation we observed that both conditions are associated to a significant increase of blood lactate. Since in our experimental conditions we can exclude a muscular production of lactate, the significant increment of peripheral blood lactate values, observed 10 min after the end of the rTMS session, is probably due to the crossing by brain-produced lactate of the blood–brain barrie