Taste Enhancement by Pulsatile Stimulation Is Receptor Based But Independent of Receptor Type

Abstract

Effects of subjects' taste sensitivity (expressed as taste detection threshold), tastant quality and taste transduction mechanism on pulsation-induced taste enhancement were tested. Taste intensities of pulsatile MSG and NaCl stimuli at pulsation periods below, at and above individual taste fusion periods (TFP in seconds) were compared to taste intensities of a continuous reference of the same net tastant concentration and quality. In line with results previously reported for sucrose, pulsation-induced taste enhancement peaked around TFP for both MSG and NaCl and did not require perception of tastant pulsation. TFP and pulsation effects were independent of the taste transduction mechanism (G-protein-coupled receptor for MSG versus ion-channel for NaCl). The absence of a relation between TFP and taste sensitivity suggests that temporal gustatory resolution and taste sensitivity are not necessarily influenced by the same factors. The results support earlier findings that early stages of taste transduction are involved in pulsation-induced taste enhancement. Pulsation-induced taste enhancement is determined by the pulsation rate (i.e. TFP) which is longer for MSG than NaCl. This is probably due to the tastant-specific interaction with the receptor rather than the taste transduction mechanism (G-protein-coupled receptor versus ion-channel) involved.

Fig. 1

Number of subjects out of 15 with individual MSG taste fusion periods (TFP_MSG(i) in seconds) equal to or smaller than the MSG taste fusion period (TFP_MSG in seconds). Dashed line represents median TFP = 10.3 s. Error bars represent standard error of four repetitions

Fig. 2

Number of subjects out of 15 with individual NaCl taste fusion periods (TFP_NaCl(i) in seconds) equal to or smaller than the NaCl taste fusion period (TFP_NaCl in seconds). Dashed line represents median TFP = 4.4 s. Error bars represent standard error of four repetitions

Fig. 3

Relative MSG taste intensities of pulsatile stimuli at pulsation periods below the taste fusion period (TFP; 0.5 × TFP_MSG), at TFP and above TFP (2 × TFP) compared to continuous MSG delivery of the same net MSG concentration (reference; 100 %). Dashed bars indicate pulsatile stimuli. Error bars express standard error (n = 6 repetitions). Samples denoted with the same letter are not significantly different at p < 0.05

Fig. 4

Relative NaCl taste intensities of pulsatile stimuli at pulsation periods below the taste fusion period (TFP; 0.25 and 0.5 × TFP_NaCl), at TFP and above TFP (2 and 4 × TFP) compared to continuous NaCl delivery of the same net NaCl concentration (reference; 100 %). Dashed bars indicate pulsatile stimuli. Error bars express standard error (n = 4 repetitions). Samples denoted with the same letter are not significantly different at p < 0.05