Induction of emesis by the sodium channel activator veratrine in the lesser spotted dogfish, Scyliorhinus canicula (Chondrichthyes : Elasmobranchii)

This study provides the first quantitative description of the emetic reflex (vomiting) in the dogfish (Scyliorhinus canicula) by using veratrine HCl ( 10 mg kg(-1), i.p.), the sodium channel activator as a stimulus. Vomiting o ccurred within 10 min of injection. The most notable features of the respon se 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 buccophary ngeal musculature and lowering of the jaw rapidly followed by the expulsion of gastric contents (pieces of fish). The expulsion sequence (ii and iii) took similar to 1 s. The significance of the vomiting reflex in the dogfish is discussed in terms of its protective function and as a component of nor mal feeding to periodically eject indigestible food residues.