This study provides the first quantitative description of the emetic reflex (vomiting) in the dogfish (Scyliorhinus canicula) by using veratrine HC1 (lOmgkg−1, i.p.), the sodium channel activator as a stimulus. Vomiting occurred within 10 min of injection. The most notable features of the response in the correct temporal sequence were: (i) head shaking with wide gaping of the mouth; (ii) lowering of the ventral buccal cavity and expansion of the pharyngeal cavity; (iii) contraction of the gill arches, the buccopharyngeal musculature and lowering of the jaw rapidly followed by the expulsion of gastric contents (pieces of fish). The expulsion sequence (ii and iii) took ~ 1 s. The significance of the vomiting reflex in the dogfish is discussed in terms of its protective function and as a component of normal feeding to periodically eject indigestible food residues.
Conversion of the sodium channel activator aconitine into a potent α7-selective nicotinic ligand