Gustatory Effects of Capsaicin that are Independent of TRPV1 Receptors

Abstract

Listen

Translate article

In order to choose which foods are palatable and safe to ingest, it is important to integrate information from different modalities, not only chemosensory (taste and olfaction), but also somatosensory (texture, irritation, nociception) (Scott and Verhagen, 2000). Capsaicin, the pungent component from chili peppers, has been shown to alter taste perception (Lawless and Stevens, 1984; Prescott and Stevenson, 1995; Simons et al., 2002) and has traditionally been added to foods to change their palatability. The effects of capsaicin on taste could emerge from the integration throughout the gustatory axis of information originating from capsaicin’s direct effects on taste receptor cells (TRCs) (Liu and Simon, 2001; Park et al., 2003; Lyall et al., 2004) and/or from information resulting from the effects of capsaicin on TRPV1 receptors in trigeminal nerve endings in the mouth (Liu and Simon, 1996, 2000). Recent studies have shown that capsaicin can alter neural responses to tastants at the level of the nucleus tractus solitarius (NTS) and that these effects seem to be independent of trigeminal transmission (Simons et al., 2003). Previously, Okuni (1977)showed that chorda tympani fibers can be activated by capsaicin, indicating capsaicin can affect the gustatory pathway and more recently, Lyall et al. (2004) presented evidence for a TRPV1 splice variant in TRCs that is responsible for the amilorideinsensitive responses to salts. Here, we found that in dissociated rat TRCs capsaicin inhibits voltage-gated inward and outward currents. Furthermore, we found that in TRPV1–/– mice capsaicin can alter taste preference to sucrose. These results demonstrate that the effects of capsaicin in taste perception do not result exclusively from the activation of capsaicin-sensitive receptors, but also through nonspecific TRPV1-independent mechanisms.