Functional Development of Nociceptors in the Oral Mucosa

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Functional Development of the oral mucosal nociceptors was investigated using in vitro Jawnerve preparation which was recently developed by ours. A total of 36 male Wistar albino rats weighing 250-350 g were tested. The animals were housed in conventional acrylic cages with soft bedding under a 14 h light/10 h dark cycle. Only one recording was obtained from each animal and the animal was sacrificed immediately after experiment with an intracardiac injection of thiamylal sodium (100 mg/kg, Isozol^【○!R】, Yoshitomi Pharmacy, Osaka, Japan). All experiments were approved by the Animal Care Welfare Committee Nagasaki University.In the oral mucosa, four subtypes of nociceptors were found: A-delta high threshold mechanonociceptor, A-delta polymodal nociceptor, C high threshold mechanonociceptor, C polymodal nocieptor. These nociceptors were maturated by 3-5 weeks after birth. The ratio of polymodal nociceptors innervated by A-delta or C afferent fiber was decreased during development.