TEMPLE, J.G.*; LAITALA, L.; Univ. of Mary Washington; Univ. of Mary Washington: Uptake and Metabolism of orally administered serotonin in the plasma of toad-eating and non-toad-eating snakes

American species of toads produce skin secretions that induce severe physiological effects when ingested by some potential predators including black rat snakes (Elaphe o. obsoleta). However, eastern hognose snakes (Heterodon platyrhinos; toad specialists) and banded water snakes (Nerodia fasciata) regularly ingest toads and suffer no noticeable adverse reactions. Among the toxin components is serotonin, which has been shown to induce a wide range of physiological effects in vertebrate cardiovascular systems ranging from vasomotor effects to alterations in cardiac performance. The uptake and metabolism of ingested serotonin in the bloodstream of E. o. obsoleta, N. fasciata and H. platyrhinos was compared. Blood plasma serotonin and 5-HIAA metabolite levels were determined prior to, and hourly for 7 hours following, oral administration of serotonin in each species. Preliminary results indicate that plasma levels of the serotonin metabolite 5-HIAA increased in a similar fashion for all three species, suggesting that the breakdown of serotonin occurs at equal rates in each species. However, the plasma 5-HT levels increased significantly in H. platyrhinos as compared to the other two species. This suggests that the breakdown of serotonin may occur in the digestive organs of E. o. obsoleta and N. fasciata prior to absorption into the bloodstream. Alternatively, absorption of serotonin from the digestive tract may be similar in all species, but serotonin may be removed from the plasma in E. o. obsoleta and N. fasciata more efficiently than in H. platyrhinos. These results suggest species-specific methods of metabolizing ingested serotonin. This project was supported by the University of Mary Washington and the Virginia Academy of Science.