Please cite this article in press as: Wolff, M., et al., Amitriptyline and carbamazepine utilize voltage-gated ion channel sup- pression to impair excitability of sensory dorsal horn neurons in thin tissue slice: An in vitro study. Neurosci. Res. (2016), http://dx.doi.org/10.1016/j.neures.2016.02.006 ARTICLE IN PRESS G Model NSR-3934; No. of Pages 12 Neuroscience Research xxx (2016) xxx–xxx Contents lists available at ScienceDirect Neuroscience Research jo ur nal homepage: www.elsevier.com/locate/neures Amitriptyline and carbamazepine utilize voltage-gated ion channel suppression to impair excitability of sensory dorsal horn neurons in thin tissue slice: An in vitro study Matthias Wolff a , Patrick Czorlich b , Chandran Nagaraj c , Rose Schnöbel-Ehehalt a , Yingji Li d , Grazyna Kwapiszewska c,e , Horst Olschewski d , Stefan Heschl e , Andrea Olschewski c,e,∗ a Department of Anaesthesiology, Intensive Care Medicine, Pain Therapy, Justus-Liebig-University, Giessen, Germany b Department of Neurosurgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany c Ludwig Boltzmann Institute for Lung Vascular Research, Graz, Austria d Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Austria e Department of Anaesthesia and Intensive Care Medicine, Medical University of Graz, Austria a r t i c l e i n f o Article history: Received 28 October 2015 Received in revised form 15 February 2016 Accepted 18 February 2016 Available online xxx Keywords: Lamina I–III Spinal cord Action potential Sensory neurons Antidepressants Firing pattern a b s t r a c t Amitriptyline, carbamazepine and gabapentin are often used for the treatment of neuropathic pain. However, their analgesic action on central sensory neurons is still not fully understood. Moreover, the expression pattern of their target ion channels is poorly elucidated in the dorsal horn of the spinal cord. Thus, we performed patch-clamp investigations in visualized neurons of lamina I–III of the spinal cord. The expression of the different voltage-gated ion channels, as the targets of these drugs, was detected by RT-PCR and immunohistochemistry. Neurons of the lamina I–III express the TTX-sensitive voltage- gated Na + as well as voltage-gated K + subunits assembling the fast inactivating (A-type) currents and the delayed rectifier K + currents. Our pharmacological studies show that tonically-firing, adapting-firing and single spike neurons responded dose-dependently to amitriptyline and carbamazepine. The ion channel inhibition consecutively reduced the firing rate of tonically-firing and adapting-firing neurons. This study provides evidence for the distribution of voltage-gated Na + and K + subunits in lamina I–III of the spinal cord and for the action of drugs used for the treatment of neuropathic pain. Our work confirms that mod- ulation of voltage-gated ion channels in the central nervous system contributes to the antinociceptive effects of these drugs. © 2016 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. 1. Introduction Spinal dorsal horn neurons are one of the key players in central sensory transmission and modulation and thus in acute pain per- ception as well as in the pathomechanism of chronic neuropathic pain syndromes (LaMotte, 1977; Light and Perl, 1979; Rethelyi, 1977). Furthermore, among the neurons in laminae I–III, tonically- firing neurons were reported to be nociceptive-specific neurons (Lopez-Garcia and King, 1994). ∗ Corresponding author at: Ludwig Boltzmann Institute for Lung Vascular Research & Experimental Anesthesiology of the Department of Anesthesia and Inten- sive Care Medicine, Medical University of Graz, Auenbruggerplatz 2.6, A-8036 Graz, Austria. Tel.: +43 316 385 72057; fax: +43 316 385 72058. E-mail address: andrea.olschewski@medunigraz.at (A. Olschewski). We described the pharmacological modulation of the voltage- gated ion channels of the sensory dorsal horn neurons in lamina I–III by local anaesthetics using the thin slice of the spinal cord combined with the patch-clamp method (Olschewski et al., 1998). During the last decades, the prime importance of voltage-gated ion channels in pain processing in these neurons has been demonstrated in exten- sive electrophysiological nociceptive studies. For action potential generation, the initial driving force is generated by sodium (Na + ) channels (Safronov et al., 1997). In lumbar dorsal horn neurons, voltage-gated potassium (K + ) channels additionally modulate the firing pattern, indicating that both Na + and K + channels are essen- tial components governing neuronal excitability (Safronov, 1999; Hess and El Manira, 2001; Olschewski et al., 2001; Melnick et al., 2004a,b). Although voltage-gated Na + and K + channels appear to be differently expressed throughout the nervous system, our knowl- edge about their distribution in the lamina I–III of dorsal spinal cord is still limited (Hildebrand et al., 2011). http://dx.doi.org/10.1016/j.neures.2016.02.006 0168-0102/© 2016 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.