Orally administered indicaxanthin is able to modulate human motor cortical excitability and plasticity

Opuntia Ficus Indica contains Indicaxanthin (IX), an antinflammatory and antioxidant betalaine pigment. This phytochemical is also able to cross the blood brain barrier (BBB) in rats and modulate neuronal activity. Considering these evidence, we aimed at investigating if orally administered IX could affect human brain tissue. 8 healthy and right-handed male subjects were recruited (20-45 years) with no history or clinical signs of neurological diseases, brain trauma or use of drugs acting on neuronal process, as assessed by a clinical neurologist. Non invasive Brain Stimulation and Neuromodulation (NIBS and NIN) instructions were applied in basal condition (T0) and 2 hours after having assumed 400 gr of cactus pear fruits (T1), over one week distance at least. Each subject experienced 30 pseudorandomised stimuli of paired pulse transcranial magnetic stimulation (ppTMS) over the M1: 10 short intracortial inhibition (SICI), 10 intracortical facilitation (ICF) and 10 test stimuli. They were delivered before and after 20 minutes of anodal transcranial Direct Current Stimulation (a-tDCS). IX significantly increased PRE-tDCS TEST (p<0.0103) and PRE-tDCS ICF (p<0.052), POST-tDCS ICF (p<0.0001) and SICI (p<0.001) were reduced, PRE-tDCS SICI was unchanged. All considered, IX is able to increase cortical excitability of human motor cortex. Finally, this nutraceutical seems to achieve an excitatory drive on motor cortical plasticity due to the paradoxical effects emerged after tDCS.