Inhibitory effect of amiloride and gadolinium on fine afferent nerves in the rat knee : evidence of mechanogated ion channels in joints

• Published in: Experimental brain research Vol. 167; no. 1; pp. 114 - 118
• Main Authors: HEPPELMANN, Bernd, MCDOUGALL, Jason J
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.11.2005; Springer Nature B.V
• Subjects: Afferent Pathways - drug effects; Amiloride - pharmacology; Animals; Biological and medical sciences; Dose-Response Relationship, Drug; Fundamental and applied biological sciences. Psychology; Gadolinium - pharmacology; Lower Extremity - innervation; Lower Extremity - physiology; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Neural Inhibition - drug effects; Physical Stimulation - methods; Rats; Rats, Wistar; Reaction Time - drug effects; Sodium Channel Blockers - pharmacology; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Time Factors; Vertebrates: nervous system and sense organs; Mechanotransduction, Stretch activated channels; Receptive field; Rat; Force; Rodentia; Discharge pattern; Central nervous system; Electrophysiology; Nervous system; Gadolinium; Ionic channel; Joint nerves; Joint; Rotation; Osteoarticular system; Vertebrata; Mammalia; Amiloride; Sodium; Modulation; Body movement; Subtype
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-005-0040-z

Synovial joints are complex sensory organs which provide continuous feedback regarding position sense and degree of limb movement. The transduction mechanisms which convert mechanical forces acting on the joint into an electrochemical signal which can then be transmitted to the central nervous system are not well understood. The present investigation examined the effect of the mechanogated ion channel blockers amiloride and gadolinium on knee joint mechanosensitivity. In deeply anaesthetised rats (sodium thiopental: 100-120 mg/kg, i.p.), single unit extracellular recordings were made from knee joint group III (Adelta) and group IV (C) primary afferents in response to mechanical rotation of the joint. Afferent firing rate was measured before and after topical application of either amiloride (0.1 mM, 1 mM) or gadolinium (250 microM) onto the receptive field of the sensory unit and recording was continued every 10 min up to a total of 50 min. With normal rotation of the knee, joint mechanosensitivity was significantly reduced by both amiloride (P<0.0001; n=10-21) and gadolinium (P=0.001; n=12) and this effect was sustained throughout the recording period. This investigation provides the first in vivo electrophysiological evidence that joint mechanotransduction involves the activation of amiloride and gadolinium-sensitive mechanogated ion channels. Future studies to determine the mechanogated ion channel subtypes present in joints and the modulation of their gating properties during inflammation may yield novel approaches for the control of arthritis pain.