Postsynaptic M1 and M3 receptors are responsible for the muscarinic enhancement of retrograde endocannabinoid signalling in the hippocampus

Authors

  • Takako Ohno-Shosaku,

    1. Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8640, Japan
    Search for more papers by this author
  • Minoru Matsui,

    1. Division of Neuronal Network, Department of Basic Medical Sciences, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
    2. Laboratory of Biomedical Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
    Search for more papers by this author
  • Yuko Fukudome,

    1. Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8640, Japan
    Search for more papers by this author
  • Jumpei Shosaku,

    1. Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8640, Japan
    Search for more papers by this author
  • Hiroshi Tsubokawa,

    1. National Institute for Physiological Sciences, Okazaki, Japan
    Search for more papers by this author
  • Makoto M. Taketo,

    1. Laboratory of Biomedical Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
    2. Department of Pharmacology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
    Search for more papers by this author
  • Toshiya Manabe,

    1. Division of Neuronal Network, Department of Basic Medical Sciences, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
    2. Division of Cell Biology and Neurophysiology, Department of Neuroscience, Faculty of Medicine, Kobe University, Kobe, Japan
    Search for more papers by this author
  • Masanobu Kano

    1. Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8640, Japan
    Search for more papers by this author

: Professor Masanobu Kano, as above.
E-mail: mkano@med.kanazawa-u.ac.jp

Abstract

The cholinergic system is crucial for higher brain functions including learning and memory. These functions are mediated primarily by muscarinic acetylcholine receptors (mAChRs) that consist of five subtypes (M1–M5). A recent study suggested a novel role of acetylcholine as a potent enhancer of endocannabinoid signalling that acts retrogradely from postsynaptic to presynaptic neurons. In the present study, we further investigated the mechanisms of this cholinergic effect on endocannabinoid signalling. We made paired whole-cell recordings from cultured hippocampal neurons, and monitored inhibitory postsynaptic currents (IPSCs). The postsynaptic depolarization induced a transient suppression of IPSCs (DSI), a phenomenon known to involve retrograde signalling by endocannabinoids. The cholinergic agonist carbachol (CCh) markedly enhanced DSI at 0.01–0.3 µm without changing the presynaptic cannabinoid sensitivity. The facilitating effect of CCh on DSI was mimicked by the muscarinic agonist oxotremorine-M, whereas it was eliminated by the muscarinic antagonist atropine. It was also blocked by a non-hydrolizable analogue of GDP (GDP-β-S) that was applied intracellularly to postsynaptic neurons. The muscarinic enhancement of DSI persisted to a substantial degree in the neurons prepared from M1-knockout and M3-knockout mice, but was virtually eliminated in the neurons from M1/M3-compound-knockout mice. CCh still enhanced DSI significantly under the blockade of postsynatpic K+ conductance, and did not significantly influence the depolarization-induced Ca2+ transients. These results indicate that the activation of postsynaptic M1 and M3 receptors facilitates the depolarization-induced release of endocannabinoids.

Ancillary