"Chemosensory function of desert toads" Dr. Takatoshi Nagai

Abstract:

Frogs and toads (amphibians) do not drink orally, but obtain water by osmotic flow across their skin. Some species of the amphibian have extended their habitat to an arid area such as the desert in Nevada and south-western Arizona, where the rainfall occurs during limited time of the year. In such an area, desert toads have developed specialized regions in their ventral skin with highly expressed aquaporins to absorb water. The toads make those regions contact hydration sources, but avoid the solution containing salt ions such as Na⁺ and K⁺. However, when amiloride (a blocker for epithelial sodium channels, ENaC) was mixed with the solution, the ability for toads to avoid Na⁺ was significantly deteriorated. This behavioral observation suggests the ventral skin of toads detects sodium salts by a transduction mechanism similar to one in the vertebrate taste system. However, in the literature taste cells are not known in the amphibian skin. Then, what type of cells transduces salt taste in desert toads? Putative chemosensory cells in the skin will be presented by our physiological and anatomical studies.

Biography:

1974 B. A., Zoology, The University of Tokyo

1979 Ph. D. The University of Tokyo

Title of Thesis Dissertation: Neural encoding of gustatory information in rat chorda tympani fibers.

1979-1981 Department of Physiology, Teikyo University School of Medicine

Assistant Professor

1982-2000 Department of Physiology, Teikyo University School of Medicine

Associate Professor (Lecturer)

2001- Department of Biology, Keio University School of Medicine

Professor of Biology