Type III taste cells in mammalian taste buds are implicated in the detection and communication of sour and some salty stimuli, as well as carbonation and water. With this variety of proposed roles, it is unclear what information activated type III cells are communicating to the CNS. To better elucidate the role of type III cells in the taste bud, we use a type III cell-specific protein (polycystic kidney disease 2-like 1) to drive Cre-dependent expression of light-sensitive channelrhodopsin

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... 2) in mouse type III taste cells. Activation of these cells with light produces a taste nerve response in both the chorda tympani and glossopharyngeal nerves, and elicits a slight but significant aversion in two-bottle preference tests in both male and female mice. Unlike previous reports (Zocchi et al., 2017), our mice did not react to blue light stimulation with sustained drinking responses. These data suggest that type III cells are capable of communicating the presence of aversive stimuli in the oral cavity, which is in line with their responsiveness to sour and high concentrations of salt stimuli. The sour-sensing type III cells of the mammalian taste bud are historically difficult to study in vivo, as sour stimulation of the tongue causes intracellular acidification in all epithelial cells, not just type III cells. The present study circumvents this issue by using Cre-dependent expression of channelrhodopsin in type III cells, so that they can be activated by blue light, rather than acid (sour). Our data suggest that type III cells communicate an aversive signal to the CNS.