Mechano- and thermosensitivity of injured muscle afferents.
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Mechano- and thermosensitivity of injured muscle afferents. / Kirillova, Irina; Rausch, Vanessa; Tode, Jan; Baron, Ralf; Jänig, Wilfrid.
In: J NEUROPHYSIOL, Vol. 105, No. 5, 5, 2011, p. 2058-2073.Research output: SCORING: Contribution to journal › SCORING: Journal article › Research › peer-review
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TY - JOUR
T1 - Mechano- and thermosensitivity of injured muscle afferents.
AU - Kirillova, Irina
AU - Rausch, Vanessa
AU - Tode, Jan
AU - Baron, Ralf
AU - Jänig, Wilfrid
PY - 2011
Y1 - 2011
N2 - Injury of limb nerves leading to neuropathic pain mostly affects deep somatic nerves including muscle nerves. Here, we investigated the functional properties of injured afferent fibers innervating the lateral gastrocnemius-soleus muscle 4-13 h [time period (TP) I] and 4-7 days (TP II) after nerve crush in anesthetized rats using neurophysiological recordings from either the sciatic nerve (165 A-, 137 C-fibers) or the dorsal root L(5) (43 A-, 28 C-fibers). Ongoing activity and responses to mechanical or thermal stimulation of the injury site of the nerve were studied quantitatively. Of the electrically identified A- and C-fibers, 5 and 38% exhibited ectopic activity, respectively, in TP I and 51 and 61%, respectively, in TP II. Thus all afferent fibers in an injured muscle nerve developed ectopic activity since ? 50% of the fibers in a muscle nerve are somatomotor or sympathetic postganglionic. Ongoing activity was present in 50% of the afferent A-fibers (TP II) and in 53-56% of the afferent C-fibers (TP I and II). In TP II, mechanical, cold, and heat sensitivity were present in 91, 63, and 52% of the afferent A-fibers and in 50, 40, and 66% of the afferent C-fibers. The cold and heat activation thresholds were 5-27 and 35-48°C, respectively, covering the noxious and innocuous range. Most afferent fibers showed combinations of these sensitivities. Mechano- and cold sensitivity had a significantly higher representation in A- than in C-fibers, but heat sensitivity had a significantly higher representation in C- than in A-fibers. These functional differences between A- and C-fibers applied to large- as well as small-diameter A-fibers. Comparing the functional properties of injured muscle A- and C-afferents with those of injured cutaneous A- and C-afferents shows that both populations of injured afferent neurons behave differently in several aspects.
AB - Injury of limb nerves leading to neuropathic pain mostly affects deep somatic nerves including muscle nerves. Here, we investigated the functional properties of injured afferent fibers innervating the lateral gastrocnemius-soleus muscle 4-13 h [time period (TP) I] and 4-7 days (TP II) after nerve crush in anesthetized rats using neurophysiological recordings from either the sciatic nerve (165 A-, 137 C-fibers) or the dorsal root L(5) (43 A-, 28 C-fibers). Ongoing activity and responses to mechanical or thermal stimulation of the injury site of the nerve were studied quantitatively. Of the electrically identified A- and C-fibers, 5 and 38% exhibited ectopic activity, respectively, in TP I and 51 and 61%, respectively, in TP II. Thus all afferent fibers in an injured muscle nerve developed ectopic activity since ? 50% of the fibers in a muscle nerve are somatomotor or sympathetic postganglionic. Ongoing activity was present in 50% of the afferent A-fibers (TP II) and in 53-56% of the afferent C-fibers (TP I and II). In TP II, mechanical, cold, and heat sensitivity were present in 91, 63, and 52% of the afferent A-fibers and in 50, 40, and 66% of the afferent C-fibers. The cold and heat activation thresholds were 5-27 and 35-48°C, respectively, covering the noxious and innocuous range. Most afferent fibers showed combinations of these sensitivities. Mechano- and cold sensitivity had a significantly higher representation in A- than in C-fibers, but heat sensitivity had a significantly higher representation in C- than in A-fibers. These functional differences between A- and C-fibers applied to large- as well as small-diameter A-fibers. Comparing the functional properties of injured muscle A- and C-afferents with those of injured cutaneous A- and C-afferents shows that both populations of injured afferent neurons behave differently in several aspects.
KW - Animals
KW - Male
KW - Rats
KW - Rats, Wistar
KW - Cold Temperature/adverse effects
KW - Hot Temperature/adverse effects
KW - Mechanoreceptors/physiology
KW - Muscle, Skeletal/innervation/physiology
KW - Nerve Crush/methods
KW - Nerve Fibers, Myelinated/physiology
KW - Nerve Fibers, Unmyelinated/physiology
KW - Neuralgia/physiopathology
KW - Neurons, Afferent/physiology
KW - Physical Stimulation/methods
KW - Thermosensing/physiology
KW - Animals
KW - Male
KW - Rats
KW - Rats, Wistar
KW - Cold Temperature/adverse effects
KW - Hot Temperature/adverse effects
KW - Mechanoreceptors/physiology
KW - Muscle, Skeletal/innervation/physiology
KW - Nerve Crush/methods
KW - Nerve Fibers, Myelinated/physiology
KW - Nerve Fibers, Unmyelinated/physiology
KW - Neuralgia/physiopathology
KW - Neurons, Afferent/physiology
KW - Physical Stimulation/methods
KW - Thermosensing/physiology
M3 - SCORING: Journal article
VL - 105
SP - 2058
EP - 2073
JO - J NEUROPHYSIOL
JF - J NEUROPHYSIOL
SN - 0022-3077
IS - 5
M1 - 5
ER -
