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| Poster #346 Non-canonical detection of glucose and fructose in gustatory afferent neurons |
| Yuryanni A. Rodriguez1, Elizabeth Pereira1, Stephen D. Roper1,2, Nirupa Chaudhari1,2 1Dept. of Physiology and Biophysics, Miami, FL, United States 2Dept. of Otolaryngology, Miami, FL, United States |
Sweet, bitter and umami tastes are transduced via TasRs. A major effector for this signaling is phospholipase Cβ2 (PLCβ2). Additionally, certain sugars including glucose are believed to act via a non-canonical pathway independent of TasRs and PLCβ2. To examine neural signals reflecting this pathway, we recorded taste-evoked Ca2+ responses in geniculate ganglion afferent neurons in male and female Plcb2-/- (ko) mice, using GCaMP3 Ca2+ imaging. The non-canonical pathway has been proposed to involve a Na-dependent glucose transporter (SGLT1) and glucose metabolism in taste bud cells. Thus, we recorded responses to glucose or fructose applied at concentrations up to 1M for 30 seconds. Under these conditions, responses to these monosaccharides were indeed observed in Plcb2 ko mice. Brief stimulation (5s) with glucose or fructose elicited responses while sucrose, a disaccharide, did only infrequently. As expected, gustatory responses to NaCl (250 mM) or citric acid (10 mM), which are not mediated via PLCβ2, showed no significant difference between Plcb2 ko and heterozygous mice (NaCl, p=0.85; citric acid, p=0.09; n=7 ko, 6 het; Mann-Whitney). We tested the premise that these non-canonical sugar responses originate from SGLT1 on taste bud cells. We found that glucose, a known substrate, and fructose, not a substrate, both at 1M, elicited equivalent responses in gustatory neurons. Further, responses to fructose and glucose were unaffected by varying [Na+] in the stimulus solutions from 0 to 100 mM NaCl. Neurons that responded directly to NaCl were excluded in this analysis to avoid confusing the results with NaCl-evoked responses. Our results confirm that a non-canonical sweet taste transduction pathway exists for glucose and fructose, but it may rely on components other than SGLT1. |