CHRM3 and central nervous system cancer: In particular, focusing on key neurotransmitter systems with blood-brain barrier-permeable agents like alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA/X<sub>c</sub> <sup>-</sup>) system, Muscarinic acetylcholine receptor M3 (CHRM3), dopamine receptor D2, monoamine oxidase A, etc., may enhance drug-repurposing research as well as development of novel anti-neuron-glioma agents.