Induction of rhythmic jaw movements by stimulation of the mesencephalic reticular formation in the guinea pig

Abstract

This study was designed to investigate whether stimulation of the mesencephalic reticular formation (MRF) induces rhythmic jaw movements (RJMs) and, if it does so, to determine the RJM-inducing region in the MRF in ketamine-anesthetized guinea pigs. The results were as follows: (1) Repetitive electrical stimulation of the MRF at the level of the red nucleus induced rhythmic EMG bursts in the anterior digastric muscle (DIG). (2) The duration and cycle time of the rhythmic DIG EMG burst induced from the medial MRF were longer than those induced from the lateral MRF. (3) Repetitive MRF stimulation after paralysis still induced rhythmic multiple-unit activities in the anterior digastric motoneuron pool. (4) Neither precollicular decerebration nor cerebellectomy affected the MRF induction of RJMs. (5) Transverse hemisection at the rostral border of the pons abolished the RJMs induced from the contralateral, but not ipsilateral, MRF. Midline section of the midbrain abolished RJMs induced from the MRF on either side. (6) A lesion in the pontine pyramidal tract abolished the RJMs induced by stimulation of the ipsilateral cortical masticatory area (CMA), but not those induced from the contralateral MRF. (7) A unilateral lesion of the oral portion of the gigantocellular reticular nucleus, where the rhythm generator for the CMA-induced RJMs is located, abolished RJMs induced from not only the CMA, but also MRF on the contralateral side. (8) Microinjection of L-glutamate into the lateral, but not medial, MRF induced RJMs similar to those elicited by repetitive electrical stimulation of the same site.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurobiological Mechanisms Involved in Sleep Bruxism

“…In addition to the cerebral cortex, other areas of the central nervous system that have been associated with the experimental genesis of RJM in animals include the lateral hypothalamus, the antero-lateral or central nuclei area of the amygdala (Schärer et al, 1967;Lund and Dellow, 1971;Nakamura and Kubo, 1978;Sasamoto and Ohta, 1982), the basal ganglia (putamen of striatum, globus pallidus, substantia nigra), the thalamic reticular nuclei (also important in sleep genesis; see Section IV), the mesencephalic reticular formation, the pontine pyramidal tract, and red nuclei (Kawamura and Tsukamoto, 1960;Schärer et al, 1967;Lund and Dellow, 1971;Schärer, 1971;Hashimoto et al, 1989). In rabbits, stimulation of the hypothalamic 'defense attack area' facilitates the jaw-closing muscle reflex, which indicates that the trigeminal sensorimotor system is activated in aggressive behavior (Landgren and Olsson, 1977).…”

GABAergic output of the basal ganglia

“…2): Apomorphine-induced mouth movements are suppressed by ablation of the SC (Chandler and Goldberg, 1984), mouth movements can be evoked by GABA A receptor blockade in the lateral deep layer of the SC (Adachi et al, 2003), and the lateral SC is thought to be critical for mouth movements (biting and licking) directed at noxious stimuli applied to the limb (Wang and Redgrave, 1997). The mouth movement region in the SC may extend to the mesencephalic reticular formation (Hashimoto et al, 1989), which may also receive inputs from the SNr (Beckstead, 1983;Yasui et al, 1994). The basal ganglia control of mouth movements is further supported by neuronal activity accompanied by natural mouth movements found in the SNr (Mora et al, 1977;Nishino et al, 1985) and other basal ganglia nuclei (Mittler et al, 1994;Masuda et al, 2001).…”

Visual Awareness Due to Neuronal Activities in Subcortical Structures: A Proposal

“…Obviously, these inhibitory connections serve to reduce or suppress the output of the tectal visual analyzer to the midbrain, medullary, and spinal motor centers (Garcia-Rill & Skinner, 1987;Hashimoto, Katayama, Ishiwata, & Nakamura, 1989;Depoortere, Sandner, & DiScalia, 1990;Garcia-Rill, Kinjo, Atsuta, Ishikawa, Webber, & Skinner, 1990). It is probable that in very primitive animals, the majority of motor activity is involuntary and generated by simple action pattern generators located in the medulla and spinal cord.…”