Neuronal mechanisms of opioid containing neuron which transmit the dental pain

Research Project

Project/Area Number	02670807
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	Morphological basic dentistry
Research Institution	Hiroshima Uniersity
Principal Investigator	MATSUSHIMA Ryotaro Hiroshima Univ. Sch. of Dent., Professor, 歯学部, 教授 (70034155)
Co-Investigator(Kenkyū-buntansha)	SATODA Takahiro Hiroshima Univ. Sch. of Dent., Research Assistant, 歯学部, 助手 (80170801) TAKAHASHI Osamu Hiroshima Univ. Sch. of Dent., Assistant Professor, 歯学部, 講師 (70163243) TASHIRO Takashi Hiroshima Univ. Sch. of Dent., Associate Professor, 歯学部, 助教授 (60109650)
Project Period (FY)	1990 – 1991
Project Status	Completed (Fiscal Year 1991)
Budget Amount *help	¥1,800,000 (Direct Cost: ¥1,800,000) Fiscal Year 1991: ¥500,000 (Direct Cost: ¥500,000) Fiscal Year 1990: ¥1,300,000 (Direct Cost: ¥1,300,000)
Keywords	Spinal Trigeminal Nucleus / Noxious Stimulation / CGRP / 三又神経脊髄路核 / CGRD
Research Abstract	Distribution of axons with calcitonin gene-related peptide (CGRP) - or/and substance P (SP) -like immunoreactivity (LI) within the sensory trigeminal nuclei was examined in the cat before and after trigeminal rhizotomy. Axons with CGRP- or SP-LI were seen throughout the principal sensory trigeminal nucleus (Vp) and spinal trigeminal nuclei, including the medullary dorsal horn (MDH) . They were densely distributed particularly in the dorsolateral part of the dorsal subnucleus of the Vp, ventromedial marginal zone of the ventral subnucleus of the Vp, dorsomedial and ventromedial parts of the oral spinal trigeminal nucleus, ventromedial and lateral marginal zones of the interpolar spinal trigeminal nucleus, and lamina I, outer part of lamina II and lamina V of the MDH. Most of the CGRP-LI axons exhibited SP-LI, while many SP-LI axons did not show CGRP-LI. After trigeminal rhizotomy, almost all CGRP-LI. axons disappeared from the ipsilateral sensory trigeminal nuclei, while a considerable number of SP-LI axons remained intact throughout the nuclei ; these SP-LI axons did not show CGRP-LI. The results indicate that CGRP-LI axons within the sensory trigeminal nuclei exhibit SP-LI and are of peripheral origin, and that SP-LI axons without CGRP-LI are of central origin. And in a rat model of peripheral inflammation, dynorphin A (1-8) like immunoreactive (DYNLI)DYN-LI trigeminal neurons were examined for contacts from CGRP-LI varicosities using a double-label method. Ipsilateral to the inflammation, CGRP-LI varicosities contacted both dendrites and somata of DYN-LI neurons lamina I, II and V in spinal trigeminal nucleus caudalis. Few such contacts were found on the contralateral side. The results suggest that opioid neurons which exhibit a dynamic change in dynorphin associated with inflammation, represent a subpopulation of neurons that receive contacts from presumptive nociceptive primary afferents.