TARDBP and amyotrophic lateral sclerosis: Moreover, simultaneous treatment of the zebrafish model of ALS with butoxamine (BTX), a β2-adrenergic receptor antagonist, and TS (β2-adrenergic receptor agonist) resulted in motor axon defects similar to those of untreated zebrafish injected with mutant TDP-43 mRNA (p > 0.05; Fig. 4E, F).