TMB 8 is a non-competitive antagonist of nicotinic acetylcholine receptors (nAChRs) with IC values of 390 and 350 nM, respectively, for human muscle-type and α3β4 subunit-containing ganglionic nAChRs expressed in TE671/RD or SH-SY5Y cells. It inhibits nicotine-induced dopamine release from rat brain synaptosomes (IC = 480 nM). TMB 8 also reduces calcium availability in smooth and skeletal muscle, blocking the contractile response in isolated rabbit aortic strip when used at a concentration of 50 µM and inhibiting calcium influx and efflux in isolated guinea pig ileum when used at a concentration of 65 µM. It has been used in the study of intracellular calcium dynamics, particularly in smooth muscle. TMB 8 also inhibits protein kinase C (PKC) activity in a dose-dependent manner.