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Monoaminergic-cholinergic interactions in the primate basal forebrain
J F Smiley1, M Subramanian, M M Mesulam
1The Cognitive Neurology and Alzheimer's Disease Center, Northwestern University Medical School, Chicago, IL 60611, USA.
Neuroscience
|September 3, 1999
Summary
Monoamine axons directly synapse with cholinergic cells in the monkey and human basal forebrain. This neuroanatomical finding reveals how norepinephrine, dopamine, and serotonin systems influence acetylcholine release in the cerebral cortex.
Area of Science:
- Neuroscience
- Neuroanatomy
- Cellular Biology
Background:
- Cholinergic cells in the nucleus basalis are crucial for cognitive functions.
- Previous studies in rats showed monoamine innervation of cholinergic cells, but primate data were lacking.
Purpose of the Study:
- To investigate the anatomical relationship between monoamine axons and cholinergic cells in the primate basal forebrain.
- To determine if monoamine systems directly innervate cholinergic basal forebrain neurons in monkeys and humans.
Main Methods:
- Single- and double-labeling immunocytochemistry in monkey and human brain tissue.
- Utilized antibodies for dopamine-beta-hydroxylase (norepinephrine), tyrosine hydroxylase (dopamine), and tryptophan hydroxylase (serotonin).
- Light and electron microscopy to visualize axon contacts and synapses.
Main Results:
- Norepinephrine, dopamine, and serotonin axons were found to extensively innervate the cholinergic cells of the basal forebrain in monkeys.
- All three monoamine systems formed frequent direct contacts and synapses with cholinergic cells.
- Similar innervation patterns were observed in the human nucleus basalis.
Conclusions:
- The study provides the first direct anatomical evidence of tripartite monoaminergic innervation of basal forebrain cholinergic neurons in primates.
- These findings suggest that norepinephrine, dopamine, and serotonin modulate cholinergic activity and subsequent acetylcholine release in the cerebral cortex.