The emetic reflex in a reptile (Crocodylus porosus)

Abstract

The emetic (vomiting) reflex in a crocodilian, Crocodylus porosus, was characterised for the first time using the plant alkaloid veratrine (5 mg kg(−)(1) i.v. or i.p.) as an emetic stimulus. The latency to the onset of vomiting was 8.0+/−0.9 min (mean +/− s.e.m., N=5 animals). Vomiting was preceded by a clearly defined set of prodromal behaviours including, in temporal sequence, rhythmic contraction of the pharynx, sneezing and jaw snapping. Expulsion of vomitus was not particularly forceful and was accompanied by lateral shaking of the head. Physiological studies revealed that vomiting was accompanied by oscillatory (9.1+/−0.7 oscillations over 29.7+/−3. 6 s, N=9 episodes in three animals) increases in intraperitoneal pressure (7.0+/−0.9 kPa, cf. 0.7+/−0.1 kPa during respiration). The significance of these results is discussed in the context of the role(s) of vomiting as a protective reflex and as a mechanism for removal of indigestible food residues (e.g. fur, claws) from the gut.