title: Long lasting activity of nociceptive muscular afferents facilitates bilateral flexion reflex pattern in the feline spinal cord.
abstract: Chronic muscular limb pain requires the adoption of motor patterns distinct from the classic ipsilateral flexion, crossed extension and corresponding reciprocal inhibitions to acute exteroceptive stimulation. Using selective chemical activation of group III/IV afferents in gastrocnemius-soleus (GS) muscles we investigated bilaterally their reflex responses conditioned by (a) acute 'myositis' induced by intramuscular carrageenan; and (b) sub-acute 'myositis' induced by infusion of complete Freund's adjuvant (CFA). Reflex transmission was detected by monosynaptic testing and c-fos staining used to identify increased neuronal activity. In all control experiments with chemical stimulation of group III/IV afferents, ipsilateral responses conformed to the flexor reflex pattern. However, the expected contralateral facilitation of GS motoneurones occurred in fewer than 50% trials while only 9% of trials induced contralateral inhibition of flexor posterior-biceps-semitendinosus (PBSt) motoneurones. During carrageenan acute myositis contralateral PBSt was transiently facilitated by selective activation of group III/IV afferents. During CFA-induced myositis, contralateral only inhibition of GS motoneurones occurred instead of any facilitation, while bidirectionally a crossed facilitation of PBST dominated. These reflex changes were mirrored in an enhanced number of neurones with enhanced c-fos expression. Muscle pain, particularly if chronically persistent, requires another behavioural response pattern than acute exteroceptive pain.
authors.affiliation: Institute of Physiology, University of Göttingen, Germany. Electronic address: eschomb@gwdg.de.
authors.forename: E D
authors.initials: ED
authors.lastname: Schomburg
authors.affiliation: Institute of Physiology, University of Göttingen, Germany; Max-Planck-Institute of Biophysical Chemistry, Göttingen, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Steffens
authors.affiliation: Department of Movement Physiology, Bogomoletz Institute of Physiology, Kiev, Ukraine.
authors.forename: A I
authors.initials: AI
authors.lastname: Pilyavskii
authors.affiliation: Department of Movement Physiology, Bogomoletz Institute of Physiology, Kiev, Ukraine.
authors.forename: V A
authors.initials: VA
authors.lastname: Maisky
authors.affiliation: Department of Neuropathology, University of Göttingen, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Brück
authors.affiliation: Max-Planck-Institute for Experimental Medicine, Göttingen, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Dibaj
authors.affiliation: Wolfson CARD, Guy's Campus, King's College London, UK.
authors.forename: T A
authors.initials: TA
authors.lastname: Sears
mesh_terms: D000818:Animals; D002351:Carrageenan / Q000494:pharmacology; D002415:Cats; D004558:Electric Stimulation; D005620:Freund's Adjuvant / Q000494:pharmacology; D009046:Motor Neurons / Q000378:metabolism; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D063806:Myalgia / Q000139:chemically induced / Q000503:physiopathology*; D009220:Myositis / Q000139:chemically induced / Q000503:physiopathology*; D009619:Nociceptors / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos; D012021:Reflex, Abnormal / Q000502:physiology*; D012023:Reflex, Monosynaptic; D013116:Spinal Cord / Q000503:physiopathology*
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D002351:Carrageenan; D005620:Freund's Adjuvant
keywords: Bilateral spinal reflex transmission; Carrageenan; Freund's adjuvant; Muscle inflammation; Sensorimotor control