title: Enhancement of oscillatory activity in the endopiriform nucleus of rats raised under abnormal oral conditions.
abstract: Endopiriform nucleus (EPN) is located deep to the piriform cortex, and has neural connections with not only neighboring sensory areas but also subcortical areas where emotional and nociceptive information is processed. Well-balanced oral condition might play an important role in stability of brain activities. When the oral condition is impaired, several areas in the brain might be affected. In the present study, we investigated whether abnormal conditions of oral region influence neural activities in the EPN. Orthodontic appliance that generates continuous force and chronic pain-related stress was fixed to maxillary incisors of rats, and raised. Field potential recordings were made from the EPN of brain slices. We previously reported that the EPN has an ability to generate membrane potential oscillation. In the present study, we have applied the same methods to assess activities of neuron clusters in the EPN. In the case of normal rats, stable field potential oscillations were induced in the EPN by application of low-frequency electrical stimulation under the medium with caffeine. In the case of rats with the orthodontic appliance, stable field potential oscillations were also induced, but both duration of oscillatory activities and wavelet number were increased. The enhanced oscillations were depressed by blockade of NMDA receptors. Thus, impairment of oral health under application of continuous orthodontic force and chronic pain-related stress enhanced neural activities in the EPN, in which up-regulation of NMDA receptors may be concerned. These findings suggest that the EPN might be involved in information processing with regard to abnormal conditions of oral region.
authors.affiliation: Department of Molecular Oral Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto, Tokushima 770-8504, Japan; Department of Oral and Maxillofacial Surgery, Kanazawa Medical University, Ishikawa, Japan; Department of Physiology, Kanazawa Medical University, Uchinada-cho 920-0293, Japan. Electronic address: hyoshimu@tokushima-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoshimura
authors.affiliation: Department of Oral and Maxillofacial Surgery, Kanazawa Medical University, Ishikawa, Japan; Department of Physiology, Kanazawa Medical University, Uchinada-cho 920-0293, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Hasumoto-Honjo
authors.affiliation: Department of Physiology, Kanazawa Medical University, Uchinada-cho 920-0293, Japan.
authors.forename: Tokio
authors.initials: T
authors.lastname: Sugai
authors.affiliation: Department of Oral and Maxillofacial Surgery, Kanazawa Medical University, Ishikawa, Japan.
authors.forename: Natsuki
authors.initials: N
authors.lastname: Segami
authors.affiliation: Department of Physiology, Kanazawa Medical University, Uchinada-cho 920-0293, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kato
mesh_terms: D000818:Animals; D001479:Basal Ganglia / Q000187:drug effects / Q000503:physiopathology*; D002110:Caffeine / Q000494:pharmacology; D059350:Chronic Pain / Q000503:physiopathology*; D004558:Electric Stimulation; D008564:Membrane Potentials; D009055:Mouth / Q000503:physiopathology*; D009967:Orthodontic Appliances; D017208:Rats, Wistar; D013315:Stress, Psychological / Q000503:physiopathology
chemical_list: D002110:Caffeine
keywords: Caffeine; Endopiriform nucleus; Noxious stimuli; Orthodontic appliance; Oscillation; Pain-related stress; Rat