Presentation Details
| Rapidly-Adapting Lingual Mechanosensory Parvalbumin+ Neurons Have Discrete Fungiform Receptive Fields but Show Evidence of Convergence with Gustatory Neurons in the Nucleus Tractus Solitarius Joseph M Breza1, Kira C Grapentine1, Thomas A Myers2, Robin F Krimm2. 1Eastern Michigan University, Ypsilanti, MI, USA.2University of Louisville, Louisville, KY, USA |
Abstract
In the trigeminal ganglion, we found that neurons expressing parvalbumin (PvalB) innervate one fungiform papilla, are low threshold rapidly adapting (RA) to mechanical force, responsive to brush stimulation, heavily myelinated, and are defined as A-fast by their conduction velocities. The rostral central (RC) subdivision of nucleus tractus solitarius (NTS) is where P2X2 expressing gustatory nerve fibers terminate. The RC subdivision of the NTS is weakly myelinated and PvalB labeling is sparse. In contrast, the rostral lateral subdivision of the NTS is heavily myelinated, PvalB labeling is robust, and continues through the laterally adjacent trigeminal nuclei. We have shown that the lateral border of the P2X2 terminal field demarcates the transition from gustatory to lingual mechanosensory. Here, we investigated whether gustatory neurons receive mechanosensory input from genetically identified PvalB neurons innervating the tongue, and whether optogenetic stimulation lingual PvalB+ neurons modulated taste responses in the NTS. Consistent with our trigeminal ganglion findings, PvalB+ neurons outside the P2X2 field were RA and A-fast. Low jitter (SD of the latency) indicated they were monosynaptic. Pvalb- neurons were slowly adapting (SA) or RA, and ranged from C to A-fast with monosynaptic or polysynaptic jitter. Gustatory neurons with lingual PvalB+ input were brush sensitive, defined as RA and A-slow, and had high jitter, suggesting polysynaptic circuitry. In contrast, Pvalb- gustatory neurons that were insensitive to brush were defined as SA or RA C-fibers, whereas PvalB- gustatory neurons that were sensitive to brush were also defined as SA or RA and ranged from C to A-fast. In a few cases, optogenetic stimulation of PvalB+ neurons innervating the tongue inhibited gustatory activity.
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