| First Author | Kim YS | Year | 2014 |
| Journal | PLoS One | Volume | 9 |
| Issue | 4 | Pages | e94080 |
| PubMed ID | 24710558 | Mgi Jnum | J:311661 |
| Mgi Id | MGI:6242943 | Doi | 10.1371/journal.pone.0094080 |
| Citation | Kim YS, et al. (2014) Central connectivity of transient receptor potential melastatin 8-expressing axons in the brain stem and spinal dorsal horn. PLoS One 9(4):e94080 |
| abstractText | Transient receptor potential melastatin 8 (TRPM8) ion channels mediate the detection of noxious and innocuous cold and are expressed by primary sensory neurons, but little is known about the processing of the TRPM8-mediated cold information within the trigeminal sensory nuclei (TSN) and the spinal dorsal horn (DH). To address this issue, we characterized TRPM8-positive (+) neurons in the trigeminal ganglion and investigated the distribution of TRPM8+ axons and terminals, and their synaptic organization in the TSN and in the DH using light and electron microscopic immunohistochemistry in transgenic mice expressing a genetically encoded axonal tracer in TRPM8+ neurons. TRPM8 was expressed in a fraction of small myelinated primary afferent fibers (23.7%) and unmyelinated fibers (76.3%), suggesting that TRPM8-mediated cold is conveyed via C and Adelta afferents. TRPM8+ axons were observed in all TSN, but at different densities in the dorsal and ventral areas of the rostral TSN, which dominantly receive sensory afferents from intra- and peri-oral structures and from the face, respectively. While synaptic boutons arising from Adelta and non-peptidergic C afferents usually receive many axoaxonic contacts and form complex synaptic arrangements, TRPM8+ boutons arising from afferents of the same classes of fibers showed a unique synaptic connectivity; simple synapses with one or two dendrites and sparse axoaxonic contacts. These findings suggest that TRPM8-mediated cold is conveyed via a specific subset of C and Adelta afferent neurons and is processed in a unique manner and differently in the TSN and DH. |
