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Abducens internuclear and ascending tract of Deiters inputs to medial rectus motoneurons in the cat oculomotor nucleus: Neurotransmitters
Author(s) -
Nguyen Lynette T.,
Spencer Robert F.
Publication year - 1999
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19990816)411:1<73::aid-cne6>3.0.co;2-7
Subject(s) - oculomotor nucleus , biology , abducens nucleus , anatomy , neuroscience , oculomotor nerve , nucleus , abducens nerve , axoplasmic transport , midbrain , central nervous system , pathology , medicine , alternative medicine , palsy
The abducens internuclear and ascending tract of Deiters (ATD) pathways are the principal excitatory inputs to medial rectus motoneurons in the oculomotor nucleus and are related to the control of conjugate horizontal eye movements. Differences in the morphology and soma‐dendritic distribution of abducens internuclear and ATD synaptic endings are correlated with known differences in the physiological properties of these independent inputs. The present study extends these observations to the ultrastructural localization of the excitatory amino acid neurotransmitters, glutamate and aspartate, using a postembedding immunogold procedure combined with the pre‐embedding immunoperoxidase localization of anterogradely transported biocytin from the abducens nucleus and the ventral lateral vestibular nucleus. Consistent with their spheroidal synaptic vesicle content and the asymmetric pre/postsynaptic membrane profile, both the abducens internuclear and ATD synaptic endings are labeled with glutamate and aspartate. However, quantitative analysis of the density of colloidal gold particles associated with mitochondria versus synaptic vesicles/axoplasmic matrix reveals significant differences in the metabolic versus neurotransmitter pools of the amino acids in the two populations of synaptic endings. The findings indicate that both aspartate and glutamate, possibly co‐localized, are the excitatory neurotransmitters utilized by abducens internuclear synaptic endings whose burst‐tonic physiological activity conveys information related to eye position to medial rectus motoneurons. By contrast, glutamate is the excitatory neurotransmitter associated with ATD synaptic endings whose high frequency burst activity is related to head velocity. J. Comp. Neurol. 411:73–86, 1999. © 1999 Wiley‐Liss, Inc.