title: Role of the lateral reticular nucleus in suppressing the jaw-opening reflex following stimulation of the red nucleus.
abstract: We found in a previous study that stimulation of the red nucleus (RN) facilitated the low-threshold afferent-evoked jaw-opening reflex (JOR) and suppressed the high-threshold afferent-evoked JOR. It has been reported that the RN projections to the contralateral lateral reticular nucleus (LRt), and stimulation of the LRt inhibits the nociceptive JOR. These facts suggest that RN-induced modulation of the JOR is mediated via the LRt. We investigated whether electrically induced lesions of the LRt, or microinjection of muscimol into the LRt, affects RN-induced modulation of the 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 either 1.2 (low-threshold) or 4.0 (high-threshold) times the threshold. Electrically induced lesion of the LRt and microinjection of muscimol into the LRt reduced the RN-induced suppression of the high-threshold afferent-evoked JOR, but did not affect the RN-induced facilitation of the low-threshold afferent-evoked JOR. These results suggest that the RN-induced suppression of the high-threshold afferent-evoked JOR is mediated by a relay in the contralateral LRt.
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 Orthodontics, School of Life Dentistry at Niigata, The Nippon Dental University, 1-8 Hamaura-cho, Chuou-ku, Niigata 951-8580, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Yajima
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; D001703:Biophysics; D001931:Brain Mapping; D004558:Electric Stimulation; D007568:Jaw / Q000502:physiology*; D008297:Male; D009434:Neural Pathways / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012012:Red Nucleus / Q000293:injuries / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012154:Reticular Formation / Q000502:physiology*
keywords: Electric lesion; Lateral reticular nucleus; Muscimol; Red nucleus; Two types of jaw-opening reflex