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| Poster #272 Genetic identification of a rapidly-adapting low-threshold mechanoreceptor innervating fungiform papillae |
| Thomas A. Myers1,2, Joseph M. Breza2, Robin F. Krimm1 1University of Louisville, Louisville, KY, United States 2Eastern Michigan University, Ypsilanti , MI, United States |
Mechanosensory neurons detect the location and textures of food. Here, I reconstructed the peripheral axon of tongue-innervating Pvalb+ to determine anatomic receptive field size and used optotagging and electrophysiology to examine Pvalb+ neuron function. Functional responses from Pvalb+ neurons were compared to the full population of low threshold mechanosensory neurons (LTMRs) that innervate the tongue. I found that Pvalb+ neurons have a small anatomical receptive field, limited to a rough area between 3800 μm2 and 6000 μm2, which is roughly the area of one or two fungiform papillae. Functionally, the Pvalb+ population consisted of only rapidly-adapting neurons while the full population of LTMRs contains both rapidly-adapting and slowly-adapting LTMRs. When we compared the spike rates of Pvalb+ neurons to the slowly-adapting neurons of the full population, we found that unlike slowly-adapting neurons, Pvalb+ neurons did not increase their spike rates to increasing forces. We then determined the conduction velocity of Pvalb+ neurons compared to the full population of LTMRs. While we found that the full population of LTMRs had a wide range of conduction velocities (C-fibers, A-slows, and A-fasts), all of the Pvalb+ neurons fell into the A-fast category. When we tested for chemical detection using high concentrations of salt and citric acid, we found that the Pvalb+ did not respond. Similarly, when we tested Pvalb+ neurons for temperature sensitivity using a temperature ramp in both the warming and cooling directions, Pvalb+ neurons were insensitive to temperature. These findings show that Pvalb-expression identifies a tongue-innervating genetic subtype with specific functional properties that is well-suited to provide information of location and texture of food in the oral cavity. |