Electrical response to acid across the dorsal epithelium of the frog tongue.

Acid stimulation produced a change in trans-epithelial potential difference across isolated dorsal epithelium of frog tongue. The responses to acetic acid, tartaric acid and citric acid were significantly greater than those to hydrochloric acid and nitric acid at the same pH. Metabolic inhibitors had no effect on the response, but local anaesthetics reversibly depressed it. The induced response was associated with a decrease in tissue resistance. Positive polarization on the mucosa increased the response, which was decreased or reversed under negative polarization. These responses may be caused by diffusion of H-ions through the tissue, and may influence sour reception in the frog.