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Glutamatergic inputs from the pedunculopontine nucleus to midbrain dopaminergic neurons in primates: Phaseolus vulgaris ‐leucoagglutinin anterograde labeling combined with postembedding glutamate and GABA immunohistochemistry
Author(s) -
Charara Ali,
Smith Yoland,
Parent André
Publication year - 1996
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(19960108)364:2<254::aid-cne5>3.0.co;2-4
Subject(s) - pedunculopontine tegmental nucleus , neuroscience , pedunculopontine nucleus , glutamatergic , tegmentum , substantia nigra , biology , anterograde tracing , pars compacta , ventral tegmental area , midbrain , dopaminergic , postsynaptic potential , glutamate receptor , nucleus , anatomy , dopamine , central nervous system , parkinson's disease , medicine , biochemistry , receptor , disease , deep brain stimulation
To verify the possibility that the pedunculopontine nucleus is a source of glutamatergic terminals in contact with midbrain dopaminergic neurons in the squirrel monkey, we used the anterograde transport of Phaseolus vulgaris ‐leucoagglutinin in combination with preembedding immunohistochemistry for tyrosine hydroxylase and for calbindin D‐28k and postembedding immunocytochemistry for glutamate and for γ‐aminobutyric acid. Following tracer injections in the pedunculopontine nucleus, numerous anterogradely labeled fibers emerged from the injection sites to innervate densely the pars compacta of the substantia nigra and ventral tegmental area. The major type of labeled fibers were thin with multiple collaterals and varicosities that established intimate contacts with midbrain dopaminergic neurons. At the electron microscopic level, the anterogradely labeled boutons were medium sized (maximum diameter between 0.9 μm and 2.5 μm) and contained numerous round vesicles and mitochondria. Postembedding immunocytochemistry revealed that 40–60% of anterogradely labeled terminals were enriched in glutamate and formed asymmetric synapses with dendritic shafts of substantia nigra and ventral tegmental area neurons. In triple‐immunostained sections, some of the postsynaptic targets to these terminals were found to be dopaminergic. In addition, 30–40% of the anterogradely labeled terminals in both regions displayed immunoreactivity for γ‐aminobutyric acid and, in some cases, formed symmetric synapses with dendritic shafts. In conclusion, our results provide the first ultrastructural evidence for the existence of synaptic contacts between glutamate‐enriched terminals from the pedunculopontine nucleus and midbrain dopaminergic neurons in primates. Our results also show that the pedunculopontine nucleus is a potential source of γ‐aminobutyric acid input to this region. These findings suggest that the pedunculopontine nucleus may play an important role in the modulation of the activity of midbrain dopaminergic cells by releasing glutamate or γ‐aminobutyric acid as neurotransmitter. © 1996 Wiley‐Liss, Inc.