ACTION OF SOME THIAMINE ANTAGONISTS ON FROG TASTE RECEPTORS

¹ Institutes of Human Physiology and General Physiology, University of Pavia, Italy

The influence of some thiamine antagonists (pyrithiamine and oxythiamine) on the response of frog taste receptors to chemical stimulation was studied. Isolated frog tongue preparations were perfused through the lingual artery with Tyrode solutions containing different amounts of pyrithiamine or oxythiamine. Pyrithiamine strongly depresses tongue receptor response to chemical stimulation. Its action however can be almost completely prevented by equimolar amounts of thiamine. Conversely oxythiamine does not affect taste receptor function even when perfused in elevated concentrations.

These results are interpreted as a proof that thiamine is essential in frog's taste receptor activation. The lack of any action of oxythiamine can be explained by considering that this substance acts as cocarboxylase antagonist only when phosphorylated and that it cannot be easily phosphorylated in vivo. Pyrithiamine, on the other side, is known to interfere with the phosphorylation of thiamine. On this basis it is suggested that thiamine may be involved in its phosphorylated form in taste receptor function.