[1][2] The main action of BIMU-8 is to increase the rate of respiration by activating an area of the brain stem known as the pre-Botzinger complex.

[7] This suggests that either the anti-respiratory depression action is mediated via a specific subtype of the 5-HT4 receptor which is activated by BIMU-8 and zacopride, but not by mosapride or tegaserod, or alternatively there may be functional selectivity involved whereby BIMU-8 and zacopride produce a different physiological response following 5-HT4 binding compared to other 5-HT4 agonists.

Another alternative to this is that the 5-HT4 agonist currently available for use in humans do not have great enough potency or bioavailability in the brain to elicit the same effects.

[6] Along with several other 5-HT4 ligands, BIMU-8 was also found to possess significant affinity for the sigma receptors, acting as a σ2 antagonist.

[8][9][10] It is unclear as yet what contribution this additional activity makes to the pharmacological profile of BIMU-8 and other 5-HT4 ligands that also show sigma affinity.