Abstract
Acetylcholine is a ubiquitous cortical neuromodulator implicated in cognition. In order to understand the potential for acetylcholine to play a role in visual attention, we studied nicotinic acetylcholine receptor (nAChR) localization and function in area V1 of the macaque. We found nAChRs presynaptically at thalamic synapses onto excitatory, but not inhibitory, neurons in the primary thalamorecipient layer 4c. Furthermore, consistent with the release enhancement suggested by this localization, we discovered that nicotine increases responsiveness and lowers contrast threshold in layer 4c neurons. We also found that nAChRs are expressed by GABAergic interneurons in V1 but rarely by pyramidal neurons, and that nicotine suppresses visual responses outside layer 4c. All sensory systems incorporate gain control mechanisms, or processes which dynamically alter input/output relationships. We demonstrate that at the site of thalamic input to visual cortex, the effect of this nAChR-mediated gain is an enhancement of the detection of visual stimuli.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Acetylcholine / metabolism
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Action Potentials / drug effects
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Animals
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Contrast Sensitivity / drug effects
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Contrast Sensitivity / physiology
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Geniculate Bodies / drug effects
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Geniculate Bodies / metabolism
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Geniculate Bodies / ultrastructure
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Interneurons / drug effects
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Interneurons / metabolism
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Interneurons / ultrastructure
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Macaca fascicularis
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Male
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Microscopy, Electron, Transmission
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Neural Inhibition / drug effects
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Neural Inhibition / physiology
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Neurons / drug effects
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Neurons / metabolism*
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Neurons / ultrastructure
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Nicotine / pharmacology*
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Nicotinic Agonists / pharmacology
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Pyramidal Cells / drug effects
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Pyramidal Cells / metabolism
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Pyramidal Cells / ultrastructure
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Receptors, Nicotinic / drug effects
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Receptors, Nicotinic / metabolism*
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Synapses / drug effects
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Synapses / metabolism
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Synapses / ultrastructure
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Visual Cortex / drug effects
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Visual Cortex / metabolism*
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Visual Cortex / ultrastructure
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Visual Pathways / drug effects
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Visual Pathways / metabolism*
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Visual Pathways / ultrastructure
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Visual Perception / drug effects
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Visual Perception / physiology*
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gamma-Aminobutyric Acid / metabolism
Substances
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Nicotinic Agonists
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Receptors, Nicotinic
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gamma-Aminobutyric Acid
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Nicotine
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Acetylcholine