BDNF and Parkinson disease: In PD, the reduced expression of brain‐derived neurotrophic factor (BDNF) and phosphorylated GSK3β in the striatum of As‐exposed rats implied that dopamine (DA) signaling was affected here, as BDNF via its receptor tropomyosin receptor kinase B activated the PI3K/Akt signaling pathway, which subsequently inhibited GSK‐3β activity [105].