著者

Shumpei Unno Masamichi Shinoda Kumi Soma Asako Kubo Barry J Sessle Tomoyuki Matsui Masatoshi Ando Junichi Asaka Katsuhiko Otsuki Hisashi Yonemoto Hiroki Onose Kousuke Sakanashi Koichi Iwata

出版者

Nihon University School of Dentistry

雑誌

Journal of Oral Science (ISSN:13434934)

巻号頁・発行日

pp.19-0512, (Released:2020-08-01)

参考文献数

31

---

To investigate neuronal activity involved in responses to noxious stimuli in conscious monkeys, the animals were subjected to a task that required them to detect a small change in facial skin temperature or light (second temperature: T2, second light: V2) relative to an initial condition (T1 or V1), and to detect changes in V2 along with a heat task. Recordings were obtained from 57 neurons in the ventral premotor cortex (PMv) during the heat or light detection task. T1 neurons and T2 neurons showed increased activity only during T1 or T2, and T1/T2 neurons were activated by both T1 and T2 stimuli. T1/T2 neurons showed an increase in firing at higher T1 temperatures, whereas T1 neurons did not. About half of the non-light/heat-sensitive T1/T2 neurons showed increased firing at higher T2 temperatures, whereas T2 neurons showed no such increase. The heat responses of heat-sensitive PMv neurons were significantly suppressed when monkeys shifted their attention from heat to light. The present findings suggest that heat-sensitive PMv neurons may be involved in motor responses to noxious heat, whereas light/heat-PMv neurons may be involved in emotional and motivational aspects of pain and inappropriate motor responses to allow escape from noxious stimuli.

著者

Masamichi Shinoda Yoshinori Hayashi Asako Kubo Koichi Iwata

出版者

Nihon University School of Dentistry

雑誌

Journal of Oral Science (ISSN:13434934)

巻号頁・発行日

pp.19-0373, (Released:2020-03-04)

参考文献数

86

被引用文献数

16

---

Nociceptive stimuli to the orofacial region are typically received by the peripheral terminal of trigeminal ganglion (TG) neurons, and noxious orofacial information is subsequently conveyed to the trigeminal spinal subnucleus caudalis and the upper cervical spinal cord (C1-C2). This information is further transmitted to the cortical somatosensory regions and limbic system via the thalamus, which then leads to the perception of pain. It is a well-established fact that the presence of abnormal pain in the orofacial region is etiologically associated with neuroplastic changes that may occur at any point in the pain transmission pathway from the peripheral to the central nervous system (CNS). Recently, several studies have reported that functional plastic changes in a large number of cells, including TG neurons, glial cells (satellite cells, microglia, and astrocytes), and immune cells (macrophages and neutrophils), contribute to the sensitization and disinhibition of neurons in the peripheral and CNS, which results in orofacial pain hypersensitivity.

著者

Jui Yen Chen Asako Kubo Masamichi Shinoda Akiko Okada-Ogawa Yoshiki Imamura Koichi Iwata

出版者

Nihon University School of Dentistry

雑誌

Journal of Oral Science (ISSN:13434934)

巻号頁・発行日

vol.62, no.1, pp.13-17, 2020 (Released:2020-01-29)

参考文献数

22

被引用文献数

7

---

Although xerostomia can cause persistent oral pain, the mechanisms underlying such pain are not well understood. To evaluate whether a phosphorylated p38 (pp38)-TRPV4 mechanism in trigeminal ganglion (TG) neurons has a role in mechanical hyperalgesia of dry tongue, a rat model of dry tongue was used to study the nocifensive reflex and pp38 and TRPV4 expression in TG neurons. The head-withdrawal reflex threshold for mechanical stimulation of the tongue was significantly lower in dry-tongue rats than in sham rats. The numbers of TRPV4- and pp38-immunoreactive cells in the TG were significantly higher in dry-tongue rats than in sham rats. Many TRPV4-IR cells were also pp38-immunoreactive. The number of TRPV1-IR cells was unchanged in the TG after induction of tongue dryness. Local injection of a TRPV4 blocker attenuated tongue mechanical hypersensitivity in dry-tongue rats. Intraganglionic injection of a selective p38 MAP kinase inhibitor eliminated tongue hypersensitivity in dry-tongue rats and suppressed TRPV4 expression in TG neurons. The present findings suggest that TRPV4 activation via p38 phosphorylation in TG neurons is involved in mechanical hypersensitivity associated with dry tongue. These mechanisms may have a role in pain associated with xerostomia.