Yoshii, K; Hashimoto, T

Brain Research [Brain Res.], vol. 791, no. 1-2, pp. 257-262, 27 Apr 1998

The suppression mechanism of NH 3 and CO sub(2) on bullfrog taste nerve responses to 0.1 mM quinine was investigated by applying them directly on the tongue surface (surface application) or at the tongue interstices through the lingual artery (interstitial application). The surface application of NH 3 and CO sub(2) reversibly suppressed the taste nerve responses with IC 50 values of 0.37 mM and 2.2 mM, respectively, whereas their hydrates were ineffective. The interstitial application of NH 3 reversibly suppressed the taste nerve responses. The surface application of CO sub(2) recovered the suppressed responses to quinine. The 4 s application of CO sub(2) prior to that of 0.1 mM quinine had the maximum effect. These results show that NH 3 -induced alkalosis and CO sub(2) -induced acidosis of taste cells, taste nerve endings, or tongue interstices surrounding them suppressed the taste nerve responses, and that the neutralization of their intracellular pH recovered these responses. The time-dependent recovery suggests that the neutralization at a layer inside taste cells, taste nerve endings, or the interstices surrounding them is critical in taste transduction.