Chemical Senses Advance Access originally published online on August 14, 2006
Chemical Senses 2006 31(9):807-812; doi:10.1093/chemse/bjl022
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TRPV1 Receptors and Nasal Trigeminal Chemesthesis
1 Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA 2 Department of Biomedical Science, Colorado State University, Fort Collins, CO 80523, USA
Correspondence to be sent to: Wayne L. Silver, Department of Biology, Wake Forest University, Winston-Salem, NC 27106, USA. e-mail: silver{at}wfu.edu
The trigeminal nerve responds to a wide variety of irritants. Trigeminal nerve fibers express several receptors that respond to chemicals, including TRPV1 (vanilloid) receptors, acid-sensing ion channels, P2X (purinergic) receptors, and nicotinic acetylcholine receptors. In order to assess whether TRPV1 plays a role in responses to a broad array of substances, TRPV1 (along with green fluorescent protein) was expressed in human embyonic kidney cells (HEK) 293t cells which were then stimulated with diverse trigeminal irritants. Calcium imaging was used to measure responses to capsaicin, amyl acetate, cyclohexanone, acetic acid, toluene, benzaldehyde, (–)-nicotine, (R)-(+)-limonene, (R)-(–)-carvone, and (S)-(+)-carvone. Three irritants (acetic acid and the 2 carvones) stimulated nontransfected controls. Two irritants (capsaicin and cyclohexanone) stimulated only transfected cells. The response could be eliminated with capsazepine, a TRPV1 blocker. The 5 remaining irritants were nonstimulatory in both nontransfected and transfected cells. Because all the compounds tested on HEK cells elicited neural responses from the ethmoid branch of the trigeminal nerve in rats, the 5 nonstimulatory compounds must do so by a non-TRPV1 receptor. These results suggest that TRPV1 serves as a receptor for both cyclohexanone and capsaicin in trigeminal nerve endings.
Key words: calcium imaging, capsaicin, ethmoid nerve, HEK 293t transfection, irritant
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