Inhibitory effect of botulinum toxin type A on the NANC system in rat respiratory models of neurogenic inflammation

This study investigated whether botulinum toxin type A (BTX-A) inhibits respiratory neurogenic inflammation in the non-adrenergic, non-cholinergic (NANC) transmitter system in rats. Neurogenic inflammation models were induced in Sprague Dawley (SD) rats through bilateral cerebral artery occlusion (BCAO) for different times (0, 30 and 60 min) or by stimulation with capsaicin at different doses (5 or 15 g/kg). Pre-Bِtzinger Complex-Spikes and the expression of substance P, synaptosomal-associated protein-25 (SNAP-25), and reactive oxygen species (ROS) were detected with or without pretreatment of rats with BTX-A (15 or 30 U/kg). BCAO reduced pre-Bot C spike activity (spike/s) and increased the breath rate (breaths/s) in an unstable pattern in comparison to controls, while pretreatment with BTX-A slightly reduced this phenomenon. Pretreatment with BTX-A inhibited BCAO- or capsaicin-induced increases in expression of SNAP-25, substance P, and ROS in a dose-dependent manner in brainstem and lung tissue. BTX-A exerts a suppressive effect on neurogenic inflammation via non-adrenergic, non-cholinergic transmitters. These results add to the body of evidence elucidating the non-cholinergic effects of BTX-A in the context of neurogenic inflammation.