title: Frequency dependent changes in mechanosensitivity of rat knee joint afferents after antidromic saphenous nerve stimulation.
abstract: The aim of the present study was to examine the effect of electrical saphenous nerve stimulation (14 V, 1-10 Hz) on the mechanosensitivity of rat knee joint afferents. The responses to passive joint rotations at defined torque were recorded from slowly conducting knee joint afferent nerve fibres (0.6-20.0 m/s). After repeated nerve stimulation with 1 Hz, the mechanosensitivity of about 79% of the units was significantly affected. The effects were most prominent at a torque close to the mechanical threshold. In about 46% of the examined nerve fibres a significant increase was obtained, whereas about 33% reduced their mechanosensitivity. The sensitisation was prevented by an application of 5 microM phentolamine, an alpha-adrenergic receptor blocker, together with a neuropeptide Y receptor blocker. An inhibition of N-type Ca(2+) channels by an application of 1 microM omega-conotoxin GVIA caused comparable changes of the mechanosensitivity during the electrical stimulation. Electrical nerve stimulation with higher frequencies resulted in a further reduction of the mean response to joint rotations. After stimulation with 10 Hz, there was a nearly complete loss of mechanosensitivity.In conclusion, antidromic electrical nerve stimulation leads to a frequency dependent transient decrease of the mechanosensitivity. A sensitisation was only obtained at 1 Hz, but this effect may be based on the influence of sympathetic nerve fibres.
authors.affiliation: Physiologisches Institut, Universität Würzburg, Röntgenring 9, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Just
authors.forename: B
authors.initials: B
authors.lastname: Heppelmann
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004558:Electric Stimulation / Q000379:methods; D007719:Knee Joint / Q000294:innervation*; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D009478:Neuropeptide Y / Q000037:antagonists & inhibitors / Q000378:metabolism; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012501:Saphenous Vein / Q000294:innervation*; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
chemical_list: D000317:Adrenergic alpha-Antagonists; D002121:Calcium Channel Blockers; D009478:Neuropeptide Y; D020866:omega-Conotoxin GVIA; D010646:Phentolamine