The influence of mechanical stimuli and of acetylsalicylic acid on the discharges of slowly conducting afferent units from normal and inflamed muscle in the rat

• Published in: Experimental brain research 1993, Vol.92 (3), p.431-440
• Main Authors: DIEHL, B, HOHEISEL, U, MENSE, S
• Format: Article
• Language: English
• Subjects: Action Potentials - drug effects; Animals; Aspirin - pharmacology; Biological and medical sciences; Blood Pressure - drug effects; Blood Pressure - physiology; Carrageenan; Female; Fundamental and applied biological sciences. Psychology; Male; Muscle Relaxation - drug effects; Myositis - chemically induced; Myositis - physiopathology; Nerve Fibers, Myelinated - drug effects; Neural Conduction - drug effects; Neurons, Afferent - drug effects; Neurons, Afferent - physiology; Nociceptors - drug effects; Physical Stimulation; Pressure; Rats; Rats, Sprague-Dawley; Sciatic Nerve - cytology; Sciatic Nerve - drug effects; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Vertebrates: nervous system and sense organs
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/BF00229031

In anaesthetized rats, the influence of an experimental inflammation and of acetylsalicylic acid (ASA) on the discharge properties of muscle receptors with slowly conducting afferent fibres was studied using a single-fibre recording technique. Following the induction of a myositis with carrageenan, the proportion of units having background activity and the frequency of the background discharge were significantly increased. The latter change was particularly prominent in high-threshold mechanosensitive (HTM) units. There was evidence for an inflammation-induced lowering of mechanical threshold in HTM units, but the change was not statistically significant. Administration of ASA intravenously led to a decrease in the frequency of background discharge in some units while others were unaffected, although they appeared to be sensitized by the inflammation. If one assumes that at least some of the HTM receptors fulfil nociceptive functions, the results suggest that the pain and tenderness of an inflamed muscle is largely due to a sensitization and hence increased activity of nociceptive muscle receptors. The sensitization is only partially abolished by ASA.