title: Microneurographic identification of spontaneous activity in C-nociceptors in neuropathic pain states in humans and rats.
abstract: C-nociceptors do not normally fire action potentials unless challenged by adequate noxious stimuli. However, in pathological states nociceptors may become hyperexcitable and may generate spontaneous ectopic discharges. The aim of this study was to compare rat neuropathic pain models and to assess their suitability to model the spontaneous C-nociceptor activity found in neuropathic pain patients. Studies were performed in normal rats (n=40), healthy human subjects (n=15), peripheral neuropathic pain patients (n=20), and in five rat neuropathic pain models: nerve crush (n=24), suture (n=14), chronic constriction injury (n=12), STZ-induced diabetic neuropathy (n=56), and ddC-induced neuropathy (n=15). Microneurographic recordings were combined with electrical stimulation to monitor activity in multiple C fibers. Stimulation at 0.25 Hz allowed spontaneous impulses to be identified by fluctuations in baseline latency. Abnormal latency fluctuations could be produced by several mechanisms, and spontaneous activity was most reliably identified by the presence of unexplained latency increases corresponding to two or more additional action potentials. Spontaneous activity was present in a proportion of mechano-insensitive C-nociceptors in the patients and all rat models. The three focal traumatic nerve injury models provided the highest proportion (59.5%), whereas the two polyneuropathy models had fewer (18.6%), and the patients had an intermediate proportion (33.3%). Spontaneously active mechano-sensitive C-nociceptors were not recorded. Microneurographic recordings of spontaneous activity in diseased C-nociceptors may be useful for both short- and long-term drug studies, both in animals and in humans.
authors: Neuroscience Technologies, Parc Científic de Barcelona, Barcelona, Spain Department of Neurology, MC Mutual, Barcelona, Spain Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences, Universitat Autònoma de Barcelona, Bellaterra, Spain Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, UK.
authors: Jordi
authors: J
authors: Serra
authors: Hugh
authors: H
authors: Bostock
authors: Romà
authors: R
authors: Solà
authors: Jordi
authors: J
authors: Aleu
authors: Elizabeth
authors: E
authors: García
authors: Barbara
authors: B
authors: Cokic
authors: Xavier
authors: X
authors: Navarro
authors: Cristina
authors: C
authors: Quiles
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000368:Aged; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology*; D009437:Neuralgia / Q000503:physiopathology*; D009619:Nociceptors / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley