Journal of Neuroscience, Vol 9, 2887-2901, Copyright © 1989 by Society for Neuroscience
Induction of rhythmic jaw movements by stimulation of the mesencephalic reticular formation in the guinea pig
N Hashimoto, T Katayama, Y Ishiwata and Y Nakamura
Department of Physiology, Faculty of Dentistry, Tokyo Medical and Dental University, Japan.
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)