Neuroleptic modulation of oral dyskinesias induced in snakes by Xenopus skin mucus

Abstract

The skin mucus of the African clawed from Xenopus laevis promotes escape from the American water snake Nerodia sipedon by inducing oral dyskinesias. As Xenopus mucus contains peptides and indoleamines with known neuroleptic properties, and because neuroleptics are the chief cause of drug-induced orofacial dyskinesias in humans, the hypothesis was tested that the neuroleptic haloperidol (HAL) would induce oral dyskinesias when given alone and would potentiate dyskinesias in Nerodia if injected prior to oral application of Xenopus mucus. Mucus alone induced yawning, gaping, fixed yawning, fixed gaping, writhing tongue movements, gular and chewing movements, and climbing behavior, but attenuated locomotor activity. HAL given IP alone at 0.05 and 0.5 μg/g was ineffective. However, HAL greatly potentiated mucus-induced yawning but attenuated the fixed gaping seen when only mucus was applied. Data support the hypothesis that Xenopus skin mucus has neuroleptic properties and that Xenopus' antipredatory defense is in part related to chemical induction of orofacial and climbing behavior in snake predators.