CHRNA4 and glioblastoma: In order to determine which specific nAChR subtype activation is associated with changes in GBM cell proliferation, the α1, α7, and α9 subunit-selective antagonists azemiopsin, α-conotoxin [A10L]PnIA, and α-conotoxin RgIA, respectively, were added to cells, along with epibatidine, acetylcholine, or choline or without any externally added agonists.