GDF11 and stroke disorder: To date, studies investigating how taVNS affects neuroplasticity have only been performed in rodent models of stroke, in which taVNS was found to upregulate neuroplasticity markers such as cyclic adenosine monophosphate (cAMP), protein kinase A (PKA), phosphorylated cAMP-response element binding (p-CREB), phospho-endothelial nitric oxide synthase (p-eNOS), BDNF, vascular endothelial growth factor (VEGF), growth differentiation factor 11 (GDF11), α7nAch receptor, GAP-43, and peroxisome proliferator- activated receptor-γ (PPAR-γ) [77].