Individual mouse taste cells respond to multiple chemical stimuli

Abstract

Sensory organs are specialized to detect and decode stimuli in terms of intensity and quality. In the gustatory system, the process of identifying and distinguishing taste qualities (e.g. bitter versus sweet) begins in taste buds. A central question in gustatory research is how information about taste quality is extracted by taste receptor cells. For instance, whether and how individual taste cells respond to multiple chemical stimuli is still a matter for debate. A recent study showed that taste cells expressing bitter-responsive taste receptors do not also express sweet-responsive taste receptors and vice versa. These results suggest that the gustatory system may use separate cellular pathways to process bitter and sweet signals independently. Results from electrophysiological studies, however, reveal that individual taste receptor cells respond to stimuli representing multiple taste qualities. Here we used non-invasive Ca 2+ imaging in slices of lingual tissue containing taste buds to address the issue of quality detection in murine taste receptor cells. We recorded calcium transients elicited by chemical stimuli representing different taste qualities (sweet, salty, sour and bitter). Many receptor cells (38 %) responded to multiple taste qualities, with some taste cells responding to both appetitive ('sweet') and aversive ('bitter') stimuli. Thus, there appears to be no strict and separate detection of taste qualities by distinct subpopulations of taste cells in peripheral gustatory sensory organs in mice.

Sour Taste Stimuli Evoke Ca 2+ and pH Responses in Mouse Taste Cells

“…We determined that 24.6 % (17/69) of taste cells responded to acid stimulation. This corresponds well with data published by Caicedo et al (2002). The amplitudes of Ca 2+ responses were directly related to ΔpH i in this subset of cells (Fig.…”

Sour Taste Stimuli Evoke Ca 2+ and pH Responses in Mouse Taste Cells

“…We determined that 24.6 % (17/69) of taste cells responded to acid stimulation. This corresponds well with data published by Caicedo et al (2002). The amplitudes of Ca 2+ responses were directly related to ΔpH i in this subset of cells (Fig.…”

A subset of broadly responsive Type III taste cells contribute to the detection of bitter, sweet and umami stimuli

“…While we do not rule out the possibility that taste cells receive input from other taste cells, our data show that BR Type III cells do not require neighboring input to respond to bitter, sweet and/or umami stimuli. Taken with these earlier studies (Caicedo et al, 2002, Gilbertson et al, 2001, Kimura & Beidler, 1961, Ozeki, 1971, Ozeki & Sato, 1972, Sato & Beidler, 1982, Sato & Beidler, 1997, Tomchik et al, 2007, Tonosaki & Funakoshi, 1984, Yoshida et al, 2009), our data support the idea that there are both selectively and broadly responsive cells in taste buds. In agreement with others (Tomchik et al, 2007, Yoshida et al, 2009), our data indicate that these broadly responsive cells are a subset of Type III taste cells and we have now shown that BR cells can independently respond to bitter, sweet and umami stimuli.…”

Kokumi Substances, Enhancers of Basic Tastes, Induce Responses in Calcium-Sensing Receptor Expressing Taste Cells

“…This value is comparable with the immunohistochemistry results (6.8% CaSR-positive cells/taste bud). Furthermore, this compares with previous estimates, in the same preparation, of 28% cells that respond to bitter [37] and 5% to umami (monopotassium L-glutamate) stimuli [24]. The threshold concentration of γEVG needed to activate a Ca 2+ response in taste cells was 3 µM, which is consistent with reports on human sensory evaluation analysis [8].…”

Sour Taste Stimuli Evoke Ca 2+ and pH Responses in Mouse Taste Cells

“…We determined that 24.6 % (17/69) of taste cells responded to acid stimulation. This corresponds well with data published by Caicedo et al (2002). The amplitudes of Ca 2+ responses were directly related to ΔpH i in this subset of cells (Fig.…”

A subset of broadly responsive Type III taste cells contribute to the detection of bitter, sweet and umami stimuli

“…While we do not rule out the possibility that taste cells receive input from other taste cells, our data show that BR Type III cells do not require neighboring input to respond to bitter, sweet and/or umami stimuli. Taken with these earlier studies (Caicedo et al, 2002, Gilbertson et al, 2001, Kimura & Beidler, 1961, Ozeki, 1971, Ozeki & Sato, 1972, Sato & Beidler, 1982, Sato & Beidler, 1997, Tomchik et al, 2007, Tonosaki & Funakoshi, 1984, Yoshida et al, 2009), our data support the idea that there are both selectively and broadly responsive cells in taste buds. In agreement with others (Tomchik et al, 2007, Yoshida et al, 2009), our data indicate that these broadly responsive cells are a subset of Type III taste cells and we have now shown that BR cells can independently respond to bitter, sweet and umami stimuli.…”

Kokumi Substances, Enhancers of Basic Tastes, Induce Responses in Calcium-Sensing Receptor Expressing Taste Cells

“…This value is comparable with the immunohistochemistry results (6.8% CaSR-positive cells/taste bud). Furthermore, this compares with previous estimates, in the same preparation, of 28% cells that respond to bitter [37] and 5% to umami (monopotassium L-glutamate) stimuli [24]. The threshold concentration of γEVG needed to activate a Ca 2+ response in taste cells was 3 µM, which is consistent with reports on human sensory evaluation analysis [8].…”

Sour Taste Stimuli Evoke Ca 2+ and pH Responses in Mouse Taste Cells

“…We determined that 24.6 % (17/69) of taste cells responded to acid stimulation. This corresponds well with data published by Caicedo et al (2002). The amplitudes of Ca 2+ responses were directly related to ΔpH i in this subset of cells (Fig.…”

A subset of broadly responsive Type III taste cells contribute to the detection of bitter, sweet and umami stimuli

“…While we do not rule out the possibility that taste cells receive input from other taste cells, our data show that BR Type III cells do not require neighboring input to respond to bitter, sweet and/or umami stimuli. Taken with these earlier studies (Caicedo et al, 2002, Gilbertson et al, 2001, Kimura & Beidler, 1961, Ozeki, 1971, Ozeki & Sato, 1972, Sato & Beidler, 1982, Sato & Beidler, 1997, Tomchik et al, 2007, Tonosaki & Funakoshi, 1984, Yoshida et al, 2009), our data support the idea that there are both selectively and broadly responsive cells in taste buds. In agreement with others (Tomchik et al, 2007, Yoshida et al, 2009), our data indicate that these broadly responsive cells are a subset of Type III taste cells and we have now shown that BR cells can independently respond to bitter, sweet and umami stimuli.…”

Kokumi Substances, Enhancers of Basic Tastes, Induce Responses in Calcium-Sensing Receptor Expressing Taste Cells

“…This value is comparable with the immunohistochemistry results (6.8% CaSR-positive cells/taste bud). Furthermore, this compares with previous estimates, in the same preparation, of 28% cells that respond to bitter [37] and 5% to umami (monopotassium L-glutamate) stimuli [24]. The threshold concentration of γEVG needed to activate a Ca 2+ response in taste cells was 3 µM, which is consistent with reports on human sensory evaluation analysis [8].…”