Mechano- and thermosensitivity of injured muscle afferents

• DOI: 10.1152/jn.00938.2010
• Publication Date: 2011-02-10T03:47:32Z
• Authors: Irina Kirillova; Vanessa H. Rausch; Jan Tode; Ralf Baron; Wilfrid Jänig
• Keywords: Male; Nerve Fibers, Unmyelinated; Hot Temperature; Nerve Crush; Nerve Fibers, Myelinated; Rats; Cold Temperature; 03 medical and health sciences; 0302 clinical medicine; Physical Stimulation; Animals; Neuralgia; Thermosensing; Neurons, Afferent; Rats, Wistar; Muscle, Skeletal; Mechanoreceptors

Injury of limb nerves leading to neuropathic pain mostly affects deep somatic including muscle nerves. Here, we investigated the functional properties injured afferent fibers innervating lateral gastrocnemius-soleus 4-13 h [time period (TP) I] and 4-7 days (TP II) after nerve crush in anesthetized rats using neurophysiological recordings from either sciatic (165 A-, 137 C-fibers) or dorsal root L(5) (43 28 C-fibers). Ongoing activity responses mechanical thermal stimulation injury site were studied quantitatively. Of electrically identified A- C-fibers, 5 38% exhibited ectopic activity, respectively, TP I 51 61%, II. Thus all an developed since ∼ 50% a are somatomotor sympathetic postganglionic. was present A-fibers 53-56% C-fibers II). In II, mechanical, cold, heat sensitivity 91, 63, 52% 50, 40, 66% C-fibers. The cold activation thresholds 5-27 35-48°C, covering noxious innocuous range. Most showed combinations these sensitivities. Mechano- had significantly higher representation than but C- A-fibers. These differences between applied large- as well small-diameter Comparing C-afferents with those cutaneous shows that both populations neurons behave differently several aspects.