• Veit-Simon Eckle, Monika Balk, Horst Thiermann, Bernd Antkowiak, and Christian Grasshoff.
• Experimental Anesthesiology Section, Department of Anesthesiology and Intensive Care Medicine, Eberhard-Karls-University, Tübingen, Germany. Electronic address: veit-simon.eckle@uni-tuebingen.de.
• Toxicol. Lett. 2016 Feb 26; 244: 167-71.

AbstractIn organotypic spinal cord-skeletal muscle co-cultures, motoneurons are driven by locomotor commands and induce contractions in surrounding muscle fibres. Using these co-cultures, it has been shown that effects of organophosphorus compounds on neuromuscular synapses can be determined in vitro. In the present study we aimed to extend this in vitro tool for pharmacologic testing of botulinum toxin B. This neurotoxin is widely used for the treatment of dystonia. Besides its effects on the neuromuscular junction, botulinum toxins may also act at centrally located synapses. Incubation with botulinum toxin B (Neurobloc(®)) induced a significant increase in muscular activity after 24, 48 and 72h. Application of the NMDA- and AMPA-receptor antagonists AP5 (20μM) and CNQX (15μM) induced a similar augmentation of muscle activity after 48 and 72h, respectively. Administration of the glycine- and GABA(A)-receptor antagonists strychnine (1μM) and bicuculline (100μM) did not alter intrinsic muscle activity. In contrast, application of a non-depolarizing muscle relaxant rocuronium bromide reduced the muscle activity in a dose-dependent manner. Our findings suggest that glutamatergic synapses in the spinal cord are more sensitive to botulinum toxin B than synaptic contacts between spinal motoneurons and muscle fibres. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

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