LAUSR

OBJECTIVES Rhodiola rosea extract is one of the most common herbal treatment for stress. Its mechanism of action in humans still need to be determined. We investigated the effect of a single dose intake of Rhodiola rosea extract on the plastic after-effects induced by anodal and cathodal motor cortex transcranial Direct Current Stimulation in humans. METHODS Twenty-eight healthy volunteers were required to intake 500 mg of either RRE or placebo. Transcranial Magnetic Stimulation was used to investigate cortical excitability. Motor threshold, recruitment of motor-evoked potentials, cortical silent period, short-interval intracortical inhibition and intracortical facilitation were assessed at different time points. Spinal excitability and peripheral nerve conduction were measured by F-response and M-wave. Furthermore, we assessed the modulation of cortical plasticity using transcranial direct current stimulation after-effects on Motor Evoked Potentials amplitudes. RESULTS Rhodiola rosea extract acute intake prevented cathodal transcranial Direct Current Stimulation-induced Long-term depression-like plasticity. The extract intake did not affect cortical excitability. CONCLUSIONS Our findings suggest that a single oral dose of Rhodiola rosea extract intake modulates cortical plasticity in humans preventing the activity-dependent reduction in the efficacy of neuronal synapses. These results suggest that the adaptogenic and antidepressant effects of Rhodiola rosea extract might be based on its modulation of brain plasticity.