Peri-threshold Trigeminal Stimulation with Capsaicin Increases Taste Sensitivity in Humans

Abstract

Introduction Taste perception is affected by trigeminal stimuli, i.e., capsaicin. This has been studied at suprathreshold concentrations. However, little is known about taste perception at threshold level in the presence of low concentration of capsaicin. The aim of the study was to explore whether taste sensitivity for sweet, sour, salt, bitter, and umami is modulated by the presence of capsaicin in the peri-threshold range. Methods Fifty-seven adults (age range 19–85 years; 32 women) with functional gustation participated in the study. Based on their perception of phenylthiocarbamide (PTC), the group was stratified into non-tasters (n = 20) and tasters (n = 37). Threshold for sweet (sucrose), sour (citric acid), salty (sodium chloride), bitter (quinine-hydrochloride), and umami (sodium-glutamate) tastes was estimated using a single-staircase paradigm (3-alternative forced choice; volume per trial 0.1 ml) with or without 0.9-µM capsaicin added. This capsaicin concentration had been determined in pilot studies to be in the range of oral perception thresholds. Results The addition of capsaicin produced lower taste thresholds for sweet, sour, salty, and bitter but not for umami. In contrast, neither PTC taster status nor sex affected these results. Conclusion The current results indicate that a low concentration of capsaicin increases gustatory sensitivity. Implications The current findings provide evidence supporting different effects of capsaicin on taste perception at threshold level. It has implications for boosting taste sensitivity or flavor enjoyment with low concentration of capsaicin.

The Individual Differences in the Perception of Oral Chemesthesis Are Linked to Taste Sensitivity

“…The reason for this might be linked to the genetic variations of TRP channels and their potential interaction with the gustatory system [31]. Taste perception studies with trigeminal stimuli of capsaicin have shown that the presence of capsaicin in the peri-threshold range reduced taste thresholds for sweet, sour, salty, and bitter but not for umami [41]. Also, a previous study focusing on chemical heat has shown that sweet, sour, salty, and bitter are influenced by the pungency of capsaicin, however, capsaicin did not influence umami [31,42].…”

Trigeminal Sensory Neuropathy Predicts Chemosensory Dysfunction After Skull Base Surgery

“…The intimate anatomic relationship of somatosensory and gustatory signal transmission pathways explains why trigeminal stimuli can interfere with taste sensitivity. [28][29][30][31] Another important finding is that the neuropathic symptoms were associated with lower trigeminal sensitivity to CO 2 . From an anatomic point of view, the intranasal trigeminal function should correlate with V1/V2 neuropathy because the ophthalmic and maxillary branches are responsible for intranasal innervation and the corresponding sensitivity to chemical stimuli.…”

“…The intimate anatomic relationship of somatosensory and gustatory signal transmission pathways explains why trigeminal stimuli can interfere with taste sensitivity. 28-31…”

Neurosensory development of the four brainstem-projecting sensory systems and their integration in the telencephalon

“…(2) a central olfactory-gustatory region; (3) a socio-emotional region in the anterior-ventral insula; and (4) a cognitive anterior-dorsal region (Uddin et al, 2017). Trigeminal and olfactory input converges and integrates within the insular region (Hummel et al, 2009) which is expanded for spicy stimulations in humans (Han et al, 2021;Spence et al, 2021). Somatosensory manifestations represent a large proportion of responses elicited by electrical stimulation of the insular cortex in humans.…”