We have developed an innovative method to record taste-evoked activity in gustatory afferent neurons with good cellular and temporal resolution. The method uses confocal functional calcium imaging and transgenic mice that express GCaMP3 in sensory neurons. By carefully exposing geniculate ganglia in living, anesthetized GCaMP3-mice and applying taste stimuli to the oral cavity, we can now record robust and reliable responses to discern the principles behind the transmission of gustatory evoked signals from taste buds to the hindbrain. These data will considerably extend single unit electrical recordings from the chorda tympani and greater superficial petrosal nerves or from geniculate ganglion cells. We are able to recording simultaneously from large ensembles of neurons. We have also designed a powerful strategy to relate the functional response profiles of individual geniculate ganglion neurons to their patterns of gene expression and establish robust molecular markers for separate functional classes of neurons. In a concerted effort from two well-established laboratories, we now propose a multi-PI project to exploit this novel preparation and to answer key questions regarding taste. Our new approach will tremendously expand our knowledge of peripheral sensory processing in taste. Our preliminary data demonstrate the feasibility of all 4 tightly-focused Specific Aims:
Aim 1 : How do gustatory sensory afferent cells respond to sweet, salty, bitter, sour, umami tastes and fats? Aim 2: Do mixtures of taste stimuli enhance responses from gustatory sensory afferent neurons? Aim 3: Do ganglion neurons that express certain transmitter receptors innervate specific taste cells? Aim 4: Are there dedicated neurons that detect each taste stimulus, and if so, can specific molecular markers be identified that associate with gustatory afferent neuron responses for each taste quality?
Salty, sweet, and fatty sensations drive seemingly insatiable food consumption. Although the appetite centers and reward circuits that cause overeating are located in the brain, the selection of highly caloric and salty foods is governed by taste pathways in the periphery. Thus, understanding how salt, sugar, and fat interact and stimulate peripheral gustatory circuits is important for understanding (and eventually controlling) overeating.
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