title: Modulation of two types of jaw-opening reflex by stimulation of the red nucleus.
abstract: The red nucleus (RN) is divided cytoarchitecturally into two parts, the parvicellular part (RPC) and the magnocellular part (RMC). The present study aims, first, to compare the effects of RN stimulation between low- and high-threshold afferents-evoked jaw opening reflexes (JORs), and secondly to compare the size of these effects in the RPC and RMC. Experiments were performed on rats anesthetized with urethane-chloralose. The JOR was evoked by electrical stimulation of the inferior alveolar nerve 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 that necessary to elicit the JOR. Conditioning electrical stimulation of the RN significantly facilitated the JOR evoked by the low-threshold afferents. On the other hand, conditioning electrical stimulation of the RN significantly suppressed the JOR evoked by the high-threshold afferents. Microinjection of monosodium glutamate into the RN also facilitated the JOR evoked by the low-threshold afferents, but suppressed that evoked by high-threshold afferents. Facilitation did not differ between the RMC and the RPC. Suppression by the RMC stimulation was significantly greater than that by the RPC stimulation. These results suggest that the RN has distinct functional roles in the control of the JOR.
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. ysatoh@ngt.ndu.ac.jp
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Satoh
authors.forename: Eriko
authors.initials: E
authors.lastname: Yajima
authors.forename: Ken'Ichi
authors.initials: K
authors.lastname: Ishizuka
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nagamine
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Iwasaki
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D018698:Glutamic Acid / Q000494:pharmacology; D007568:Jaw / Q000502:physiology*; D008297:Male; D008340:Mandibular Nerve / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012012:Red Nucleus / Q000187:drug effects / Q000502:physiology*; D012018:Reflex
chemical_list: D018698:Glutamic Acid
keywords: Electrical stimulation; Glutamate; Red nucleus magnocellular part; Red nucleus parvicelluar part; Two types of jaw-opening reflex