Magnetically induced motor evoked potentials and H-reflex during nembutal and ketamine anesthesia administration in rats.
The effects of nembutal and ketamine anesthesia on motor evoked potentials (MEPs) and spinal segment reflex (H-response, F and M waves) were investigated in rats by magnetic stimulation. These potentials were generated by magnetic stimulation of the motor cortex and the spinal cord (L4-L5). After application of nembutal, MEP and H-response decreased in amplitude, eventually disappearing. The amplitudes of F and M waves increased and persisted at the increased levels during anesthesia. The latencies of F and M waves were constant before and after anesthesia. Following ketamine administration, the threshold, latency and amplitude of the magnetically induced MEPs, and M, F and H responses were not influenced systematically. The results suggested that MEPs and H-response depression and/or disappearance due to synaptic site suppression after nembutal anesthesia, and the increase and persistence of increased F and M waves amplitudes were all due to the increasing motoneuron excitability, whereas ketamine did not affect synaptic sites subjected to magnetic stimulation.
Department of Physiology, Kinki University School of Medicine, Osaka-Sayama, Osaka, Japan. kchiba@med.kindai.ac.jp
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Chiba
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Nakanishi
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Hiruma
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Satou
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Hashimoto
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Chichibu
D000758:Anesthesia; D000777:Anesthetics / Q000008:administration & dosage*; D000818:Animals; D004576:Electromyography / Q000187:drug effects; D019054:Evoked Potentials, Motor / Q000187:drug effects*; D006181:H-Reflex / Q000187:drug effects*; D007649:Ketamine / Q000008:administration & dosage*; D008280:Magnetics; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D010424:Pentobarbital / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000502:physiology; D013569:Synapses / Q000187:drug effects / Q000502:physiology
D000777:Anesthetics; D007649:Ketamine; D010424:Pentobarbital