Figure 3. Mechanosensory feedback enhances the recruitment of spinal motor neurons during active locomotion.
(A) To compare the recruitment of spinal motor neurons when mechanosensory feedback was present (‘active locomotion’) or suppressed (‘fictive locomotion’), we conducted bioluminescence assays in 4 dpf Tg(mnx1:gal4;UAS:GFP-aequorin-opt) zebrafish larvae before and after paralysis using pancuronium bromide, and in immotile 4 dpf Tg(mnx1:gal4;UAS:GFP-aequorin-opt;cacnb1ts25/ts25) mutants compared to their motile siblings. (B) Bioluminescence signals from motor neurons revealed a marked decrease in bioluminescence amplitude after paralysis. (C) Quantification of the change in mean bioluminescence amplitude (before paralysis: 26.6 ± 0.9 photons/10 ms; after paralysis: 11.1 ± 0.4 photons/10 ms, n = 10 larvae in each group, 30 trials per larva, p<0.001). (D) Similarly, averaged bioluminescence signals from motor neurons were markedly decreased in immotile Tg(mnx1:gal4;UAS:GFP-aequorin-opt;cacnb1ts25/ts25,) mutant larvae when compared with motile siblings. (E) Mean bioluminescence amplitude in motile siblings (37.6 ± 1.4 photons/10 ms) compared to immotile mutants (9.8 ± 0.4 photons/10 ms, n = 300 trials in 10 larvae for each group, p<0.001).