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The Journal of Neurophysiology Vol. 86 No. 6 December 2001, pp. 3043-3055
Copyright ©2001 by the American Physiological Society
7 and
4
2 Subtypes
Differentially Control GABAergic Input to CA1 Neurons in Rat
Hippocampus
1Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, Maryland 21201; 2Departamento de Farmacologia Básica e Clínica, Instituto de Ciências Biomédicas, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21944, Brazil
Alkondon, Manickavasagom and
Edson X. Albuquerque.
Nicotinic Acetylcholine Receptor
7 and
4
2 Subtypes
Differentially Control GABAergic Input to CA1 Neurons in Rat
Hippocampus. J. Neurophysiol. 86: 3043-3055, 2001. The hippocampus, a limbic brain region involved in
the encoding and retrieval of memory, has a well-defined structural
network assembled from excitatory principal neurons and inhibitory
interneurons. Because the GABAergic interneurons form synapses onto
both pyramidal neurons and interneurons, the activation of nicotinic
acetylcholine receptors (nAChRs) present on certain interneurons could
induce either inhibition or disinhibition in the hippocampal circuitry. To understand the role of nAChRs in controlling synaptic transmission in the hippocampus, we evaluated the magnitude of nAChR-modulated GABAergic postsynaptic currents (PSCs) in pyramidal neurons and various
interneurons of the CA1 region. Using whole cell patch-clamp recording
and post hoc identification of neuronal types in rat hippocampal
slices, we show that brief (12-s) nAChR activation by ACh (1 mM) or
choline (10 mM) enhances the frequency of GABAergic PSCs in both
pyramidal neurons and CA1 interneurons. The magnitude of
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nAChR-mediated GABAergic inhibition, as assessed by the net charge of
choline-induced PSCs, was highest in stratum lacunosum moleculare
interneurons followed by pyramidal neurons and s. radiatum interneurons. In contrast, the magnitude of
4
2 nAChR-mediated GABAergic inhibition, as assessed by the difference between the net
charge of PSCs induced by ACh and choline, was highest in pyramidal
neurons followed by s. lacunosum moleculare and s. radiatum interneurons. The present results suggest that cholinergic cues transmitted via specific subtypes of nAChRs modify the synaptic function in the hippocampus by inducing a differential degree of
GABAergic inhibition in the target neurons.
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