Self- and cross-desensitization of oral irritation by menthol and cinnamaldehyde (CA) via peripheral interactions at trigeminal sensory neurons.
Menthol and cinnamaldehyde (CA) are plant-derived spices commonly used in oral hygiene products, chewing gum, and many other applications. However, little is known regarding their sensory interactions in the oral cavity. We used a human psychophysics approach to investigate the temporal dynamics of oral irritation elicited by sequential application of menthol and/or CA, and ratiometric calcium imaging methods to investigate activation of rat trigeminal ganglion (TG) cells by these agents. Irritancy decreased significantly with sequential oral application of menthol and CA (self-desensitization). Menthol cross-desensitized irritation elicited by CA, and vice versa, over a time course of at least 60 min. Seventeen and 19% of TG cells were activated by menthol and CA, respectively, with ∼50% responding to both. TG cells exhibited significant self-desensitization to menthol applied at a 5, but not 10, min interval. They also exhibited significant self-desensitization to CA at 400 but not 200 μM. Menthol cross-desensitized TG cell responses to CA. CA at a concentration of 400 but not 200 μM also cross-desensitized menthol-evoked responses. The results support the argument that the perceived reductions in oral irritancy and cross-interactions between menthol and CA and menthol observed (at least at short interstimulus intervals) can be largely accounted for by the properties of trigeminal sensory neurons innervating the tongue.
Department of Neurobiology, Physiology & Behavior, University of California Davis, 1 Shields Avenue, Davis, California 95616, USA.
Amanda H
AH
Klein
Mirela Iodi
MI
Carstens
Karen L
KL
Zanotto
Carolyn M
CM
Sawyer
Margaret
M
Ivanov
Susan
S
Cheung
E
E
Carstens
D000171:Acrolein / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007509:Irritants / Q000494:pharmacology; D008297:Male; D008610:Menthol / Q000494:pharmacology*; D009055:Mouth / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012668:Trigeminal Ganglion / Q000502:physiology*
D007509:Irritants; D008610:Menthol; D000171:Acrolein; C012843:cinnamaldehyde