PT  - JOURNAL ARTICLE
AU  - Nicolas Wanaverbecq
AU  - Alexey Semyanov
AU  - Ivan Pavlov
AU  - Matthew C. Walker
AU  - Dimitri M. Kullmann
TI  - Cholinergic Axons Modulate GABAergic Signaling among Hippocampal Interneurons via Postsynaptic α7 Nicotinic Receptors
AID  - 10.1523/JNEUROSCI.1732-07.2007
DP  - 2007 May 23
TA  - The Journal of Neuroscience
PG  - 5683--5693
VI  - 27
IP  - 21
4099  - http://www.jneurosci.org/content/27/21/5683.short
4100  - http://www.jneurosci.org/content/27/21/5683.full
SO  - J. Neurosci.2007 May 23; 27
AB  - Homopentameric α7 nicotinic receptors have a high affinity for acetylcholine (ACh), are permeable to Ca2+ ions, and are abundant in hippocampal interneurons. Although nicotinic agonists evoke inward currents and Ca2+ transients in stratum radiatum interneurons, the role of endogenous ACh in modulating synaptic integration by interneurons is incompletely understood. Many cholinergic axonal varicosities do not have postsynaptic specializations, but α7 receptors frequently occur close to synaptic GABAA receptors. These observations raise the possibility that α7 nicotinic receptors activated by ACh released from cholinergic axons modulate GABAergic transmission in interneurons. We show that agonists of α7 receptors profoundly depress GABAergic IPSCs recorded in stratum radiatum interneurons in the CA1 region of the hippocampus. This depression is accompanied by a small increase in GABA release. α7 nicotinic receptor agonists also depress GABA- or muscimol-evoked currents in interneurons, indicating that the major effect is a postsynaptic modulation of GABAA receptors. The depression of GABA-evoked currents is abolished by chelating Ca2+ in the recorded interneuron and attenuated by inhibitors of PKC. We also show that stimuli designed to release endogenous ACh from cholinergic axons evoke an α7 receptor-dependent heterosynaptic depression of GABAergic IPSCs in interneurons. This heterosynaptic modulation is amplified by blocking cholinesterases. These results reveal a novel mechanism by which cholinergic neurons modulate information processing in the hippocampus.