• Shin Onizuka, Ryuuji Tamura, Tetsu Yonaha, Nobuko Oda, Naweed I Syed, Tetsuro Shirasaka, and Isao Tsuneyoshi.
• Department of Anesthesiology and Intensive Care, Faculty of Medicine, University of Miyazaki, Kiyotake-Cho, Miyazaki, 889-1692, Japan. pirotann@med.miyazaki-u.ac.jp
• J Anesth. 2012 Feb 1;26(1):45-53.

PurposeNerve growth factor (NGF) has been reported to affect synaptic transmission and cause neuropathic pain. In contrast, lidocaine has been used to reduce neuropathic pain; however, the effect of NGF and lidocaine on spontaneous transmitter release and synapse excitation has not been fully defined. Therefore, the effect of NGF and lidocaine on nerve regeneration, synapse reformation, and subsequent spontaneous transmitter release was investigated. We used Lymnaea stagnalis soma-soma-identified synaptic reconstruction to demonstrate that a transient increase in both frequency and amplitude of spontaneous events of miniature endplate potentials (MEPPs) occurs following NGF treatment and a short burst of action potentials in the presynaptic cell; in addition, the effect of lidocaine on NGF-induced synapse reformation was investigated.MethodsUsing a cell culture and electrophysiological and FM-143 imaging techniques for exocytosis on unequivocally identified presynaptic visceral dorsal 4 (VD4) and postsynaptic somata left pedal (LPeE) neurons from the mollusc Lymnaea stagnalis, the effects of NGF and lidocaine on nerve regeneration, synapse reformation, and its electrophysiological spontaneous synaptic transmission between cultured neurons were described.ResultsNGF increased axonal growth, frequency, and amplitudes of MEPPs. Lidocaine exposure during synapse reformation periods was drastically and permanently reduced axonal growth and the incidence of synapse excitation by NGF.ConclusionNGF increased amplitudes and frequencies of MEPPs and induced synaptic excitation by increasing axonal growth and exocytosis. Lidocaine exposure during synapse reformation periods permanently suppressed NGF-induced excitation by suppressing axonal growth and exocytosis of presynaptic neurons in the identified reconstructed synapse of L. stagnalis.

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