title: Role of the red nucleus in suppressing the jaw-opening reflex following stimulation of the raphe magnus nucleus.
abstract: In a previous study, we found that electrical and chemical stimulation of the red nucleus (RN) suppressed the high-threshold afferent-evoked jaw-opening reflex (JOR). It has been reported that the RN receives bilaterally projection fibers from the raphe magnus nucleus (RMg), and that stimulation of the RMg inhibits the tooth pulp-evoked nociceptive JOR. These facts imply that RMg-induced inhibition of the JOR could be mediated via the RN. The present study first examines whether stimulation of the RMg suppresses the high-threshold afferent-evoked JOR. The JOR was evoked by electrical stimulation of the inferior alveolar nerve (IAN), and was recorded as the electromyographic response of the anterior belly of the digastric muscle. The stimulus intensity was 4.0 (high-threshold) times the threshold. Conditioning electrical stimulation of the RMg significantly suppressed the JOR. A further study then examined whether electrically induced lesions of the RN or microinjection of muscimol into the RN affects RMg-induced suppression of the JOR. Electrically induced lesions of the bilateral RN and microinjection of muscimol into the bilateral RN both reduced the RMg-induced suppression of the JOR. These results suggest that RMg-induced suppression of the high-threshold afferent-evoked JOR is mediated by a relay in the RN.
authors.affiliation: Department of Physiology, School of Life Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Chuou-ku, Niigata 951-8580, Japan. Electronic address: ysatoh@ngt.ndu.ac.jp.
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Satoh
authors.affiliation: Department of Physiology, School of Life Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Chuou-ku, Niigata 951-8580, Japan.
authors.forename: Ken'Ichi
authors.initials: K
authors.lastname: Ishizuka
authors.affiliation: Department of Physiology, School of Life Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Chuou-ku, Niigata 951-8580, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Iwasaki
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D004576:Electromyography; D007568:Jaw / Q000294:innervation*; D008297:Male; D009434:Neural Pathways / Q000502:physiology*; D065846:Nucleus Raphe Magnus / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012012:Red Nucleus / Q000502:physiology*; D012018:Reflex / Q000502:physiology*
keywords: Electric lesion; Jaw-opening reflex; Muscimol; Raphe magnus nucleus; Red nucleus