title: No evidence for role of extracellular choline-acetyltransferase in generation of gamma oscillations in rat hippocampal slices in vitro.
abstract: Acetylcholine (ACh) is well known to induce persistent γ-oscillations in the hippocampus when applied together with physostigmine, an inhibitor of the ACh degrading enzyme acetylcholinesterase (AChE). Here we report that physostigmine alone can also dose-dependently induce γ-oscillations in rat hippocampal slices. We hypothesized that this effect was due to the presence of choline in the extracellular space and that this choline is taken up into cholinergic fibers where it is converted to ACh by the enzyme choline-acetyltransferase (ChAT). Release of ACh from cholinergic fibers in turn may then induce γ-oscillations. We therefore tested the effects of the choline uptake inhibitor hemicholinium-3 (HC-3) on persistent γ-oscillations either induced by physostigmine alone or by co-application of ACh and physostigmine. We found that HC-3 itself did not induce γ-oscillations and also did not prevent physostigmine-induced γ-oscillation while washout of physostigmine and ACh-induced γ-oscillations was accelerated. It was recently reported that ChAT might also be present in the extracellular space (Vijayaraghavan et al., 2013). Here we show that the effect of physostigmine was prevented by the ChAT inhibitor (2-benzoylethyl)-trimethylammonium iodide (BETA) which could indicate extracellular synthesis of ACh. However, when we tested for effects of extracellularly applied acetyl-CoA, a substrate of ChAT for synthesis of ACh, physostigmine-induced γ-oscillations were attenuated. Together, these findings do not support the idea that ACh can be synthesized by an extracellularly located ChAT.
authors.affiliation: Institute of Neurophysiology, Charité Universitätsmedizin Berlin, 14195 Berlin, Germany.
authors.forename: J O
authors.initials: JO
authors.lastname: Hollnagel
authors.affiliation: Institute of Neurophysiology, Charité Universitätsmedizin Berlin, 14195 Berlin, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Ul Haq
authors.affiliation: Institute of Neurophysiology, Charité Universitätsmedizin Berlin, 14195 Berlin, Germany.
authors.forename: C J
authors.initials: CJ
authors.lastname: Behrens
authors.affiliation: Institute of Neurophysiology, Charité Universitätsmedizin Berlin, 14195 Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Maslarova
authors.affiliation: Department of Neurology, The David Geffen School of Medicine at the University of California, Los Angeles, CA 90095, USA; Department of Physiology, The David Geffen School of Medicine at the University of California, Los Angeles, CA 90095, USA.
authors.forename: I
authors.initials: I
authors.lastname: Mody
authors.affiliation: Institute of Neurophysiology, Charité Universitätsmedizin Berlin, 14195 Berlin, Germany; NeuroCure Research Center, Charité Universitätsmedizin Berlin, 14195 Berlin, Germany. Electronic address: Uwe.Heinemann@charite.de.
authors.forename: U
authors.initials: U
authors.lastname: Heinemann
mesh_terms: D000105:Acetyl Coenzyme A / Q000008:administration & dosage / Q000378:metabolism; D000109:Acetylcholine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D056654:CA3 Region, Hippocampal / Q000187:drug effects / Q000201:enzymology*; D002794:Choline / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018678:Cholinergic Agents / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000201:enzymology*; D065818:Gamma Rhythm / Q000187:drug effects / Q000502:physiology*; D006426:Hemicholinium 3 / Q000494:pharmacology; D008297:Male; D008839:Microelectrodes; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D017208:Rats, Wistar; D046509:Tissue Culture Techniques
chemical_list: D018678:Cholinergic Agents; D002800:Cholinesterase Inhibitors; D014179:Neurotransmitter Uptake Inhibitors; C017058:(2-benzoylethyl)trimethylammonium; D006426:Hemicholinium 3; D000105:Acetyl Coenzyme A; D010830:Physostigmine; D002795:Choline O-Acetyltransferase; D002794:Choline; D000109:Acetylcholine
keywords: (2-benzoylethyl)-trimethylammonium iodide (BETA); acetyl-CoA; acetylcholine; hemicholinium-3 (HC-3); physostigmine; γ-oscillations in hippocampal area CA3