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The Journal of Neuroscience, July 28, 2004, 24(30):6751-6754; doi:10.1523/JNEUROSCI.1528-04.2004
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BRIEF COMMUNICATION
GABA, Not Glutamate, Controls the Activity of Substantia Nigra Reticulata Neurons in Awake, Unrestrained Rats
François Windels and
Eugene A. Kiyatkin
Behavioral Neuroscience Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland 21224
Substantia nigra pars reticulata (SNr) receives both GABAergic and glutamatergic (GLU) inputs that are believed to act together to regulate neuronal activity in this structure. To examine the role of these inputs, single-unit recording was coupled with iontophoresis of GLU and GABA in rats under two conditions: awake, unrestrained and under chloral hydrate anesthesia. Although GABA potently inhibited SNr cells in both conditions, freely moving rats showed lower sensitivity than anesthetized animals. Likewise, GLU effectively induced excitations in most SNr neurons in anesthetized animals but was much less effective in awake, unrestrained animals in terms of both the number of sensitive cells and the magnitude of GLU-induced excitation. These findings, along with consistent excitations induced by bicuculline in awake, unrestrained rats, suggest that modulation of GABA inhibitory input, not the opposing actions of GLU and GABA, is the primary factor that regulates the activity state of SNr neurons.
Key words: substantia nigra; GABA; glutamate; bicuculline; single-unit recording; freely moving animals; iontophoresis; anesthesia; basal ganglia
Received April 22, 2004;
revised June 4, 2004;
accepted June 8, 2004.
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