Publications (2)9.41 Total impact
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Article: Effect of local and intravenous lidocaine on ongoing activity in injured afferent nerve fibers.
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ABSTRACT: Lidocaine applied systemically or locally attenuates neuropathic pain in patients. Here we tested the hypothesis that ectopic activity in injured afferent A- or C-fibers is suppressed by lidocaine. In rats the sural nerve (skin nerve) or lateral gastrocnemius-soleus nerve (muscle nerve) was crushed. Four to 11 days after crush lesion afferent fibers were isolated from the lesioned nerves in bundles rostral to the injury site. Ongoing ectopic activity was recorded from 75 A-fibers (muscle N=43, skin N=32) and 69 C-fibers (muscle N=30, skin N=39). Most afferent fibers were functionally characterized by their responses to mechanical and thermal (mostly heat) stimuli applied at or distal to the nerve injury site. Low-threshold cold-sensitive cutaneous C-fibers were excluded from the analysis. Lidocaine was either applied to the nerve at or distal to the injury site in concentrations of 1 to 1000 μg/mL or injected i.v. in doses of 0.09 to 9 mg/kg (skin) or 0.047 to 4.7 mg/kg (muscle). Local application of lidocaine depressed ectopic activity in A- and C-fibers dose-dependently. Depression was weaker in C- than in A-fibers. Intravenous application of lidocaine depressed ongoing ectopic activity in A- and C-fibers dose-dependently. Responses to heat or mechanical stimulation of the injured nerve were not suppressed at the highest concentrations of lidocaine. The results support the hypothesis that decrease of neuropathic pain following local or systemic application of a local anesthetic is related to decrease of ectopic ongoing activity in injured afferent nerve fibers.Pain 07/2011; 152(7):1562-71. · 5.78 Impact Factor -
Article: Axonal thermosensitivity and mechanosensitivity of cutaneous afferent neurons.
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ABSTRACT: We hypothesized that cutaneous afferent myelinated fibers (A-fibers) and afferent unmyelinated fibers (C-fibers) respond to the same natural stimuli applied to their axons as to their terminals in the skin. In anesthetized rats, activity was recorded from afferent axons in strands isolated proximally from the sural nerve. Mechanical, cold or heat stimuli were applied to the skin or along a 15-mm length of the distal sural nerve. One-hundred and eighteen A-fibers and 109 C-fibers were characterized by their conduction velocity and/or shape of their action potentials, and by their responses to natural stimulation of the skin. Then, these fibers were tested for their responses to the same stimuli applied to the nerve. In some cases, the nerve was crushed distally after the nerve fibers had been characterized by their responses to physiological stimulation of the skin, and the responses to stimuli applied to the nerve proximal to the lesion were tested again. Almost all non-nociceptive cold-sensitive (type 1) C-fibers (97%) could be activated by cold stimuli applied to the nerve. Of nociceptive cold-sensitive (type 2) C-fibers, 39% were activated by cold stimuli applied to the nerve. Furthermore, 34% of heat-sensitive C-fibers could be activated by heating the nerve. In contrast, only 2-4% of mechanosensitive A-fibers and C-fibers responded to mechanical stimuli applied to the nerve. In conclusion, cold and heat sensitivity of cutaneous afferent neurons is not restricted to their terminals in the skin, but often extends along the axons in the nerve. Mechanosensitivity is restricted to the afferent endings in the skin.European Journal of Neuroscience 11/2010; 33(1):110-8. · 3.63 Impact Factor
