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"Dopamine is of special interest since its imbalance may produce
changes in basal ganglia activity, which generates abnormal movements,
including jaw motor dysfunction, as in oral dyskinesia and possibly in
bruxism."

"Therefore, we suggested that catecholamines may regulate oralfacial
movements through the premotor brainstem nuclei, which are related to
masticatory control, and forebrain areas related to autonomic and
stress responses"

-Sue

Neurosci Lett. 2005 Sep 23;386(1):34-9.
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Alternative pathways for catecholamine action in oral motor control.

Mascaro MB, Bittencourt JC, Casatti CA, Elias CF.

Laboratory of Chemical Neuroanatomy, Department of Anatomy, Institute
of Biomedical Sciences, University of Sao Paulo - USP, Av. Prof. Lineu
Prestes, 2415 Ed. B-III, 05508-900 Sao Paulo, SP, Brazil. mmcelo@usp.br

Orofacial movement is a complex function performed by facial and jaw
muscles. Jaw movement is enacted through the triggering of motoneurons
located primarily in the trigeminal motor nucleus (Mo5). The Mo5 is
located in the pontine reticular formation, which is encircled by
premotor neurons. Previous studies using retrograde tracers have
demonstrated that premotor neurons innervating the Mo5 are distributed
in brainstem areas, and electrophysiological studies have suggested the
existence of a subcortical relay in the corticofugal-Mo5 pathway.
Various neurotransmitters have been implicated in oral movement.
Dopamine is of special interest since its imbalance may produce changes
in basal ganglia activity, which generates abnormal movements,
including jaw motor dysfunction, as in oral dyskinesia and possibly in
bruxism. However, the anatomical pathways connecting the dopaminergic
systems with Mo5 motoneurons have not been studied systematically.
After injecting retrograde tracer fluorogold into the Mo5, we observed
retrograde-labeled neurons in brainstem areas and in a few forebrain
nuclei, such as the central nucleus of the amygdala, and the
parasubthalamic nucleus. By using dual-labeled immunohistochemistry, we
found tyrosine hydroxylase (a catecholamine-processing enzyme)
immunoreactive fibers in close apposition to retrograde-labeled neurons
in brainstem nuclei, in the central nucleus of the amygdala and the
parasubthalamic nucleus, suggesting the occurrence of synaptic
contacts. Therefore, we suggested that catecholamines may regulate
oralfacial movements through the premotor brainstem nuclei, which are
related to masticatory control, and forebrain areas related to
autonomic and stress responses.

PMID: 15978723 [PubMed - indexed for MEDLINE]