Pain
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A spared nerve injury of the sciatic nerve (SNI) or a segmental lesion of the L5 and L6 spinal nerves (SNL) lead to behavioral signs of neuropathic pain in the territory innervated by adjacent uninjured nerve fibers, while a chronic constriction injury (CCI) results in pain sensitivity in the affected area. While alterations in voltage-gated sodium channels (VGSCs) have been shown to contribute to the generation of ectopic activity in the injured neurons, little is known about changes in VGSCs in the neighboring intact dorsal root ganglion (DRG) neurons, even though these cells begin to fire spontaneously. ⋯ In intact DRGs and in neighboring non-injured neurons, the expression and the distribution among the A- and C-fiber neuronal populations of Nav1.8 and Nav1.9 was, however, unchanged. While it is unlikely, therefore, that a change in the expression of TTX-resistant VGSCs in non-injured neurons contributes to neuropathic pain, it is essential that molecular alterations in both injured and non-injured neurons in neuropathic pain models are investigated.
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We recorded evoked potentials (EPs) induced by conventional transcutaneous electrical stimulation (TS), laser stimulation (LS) and epidermal electrical stimulation (ES) using a specially made needle electrode. We evaluated the activated fibers by epidermal stimulation by assessing the conduction velocity (CV) of the peripheral nerves. The EPs were recorded from Cz electrode (vertex) of the International 10-20 system in 12 healthy subjects. ⋯ The CVs were 15.1, 15.3 and 44.1 m/s obtained by ES, LS and TS, respectively. The CV indicated that the fibers activated by the ES were mainly A fibers, which corresponded to the fibers stimulated by the LS. We considered that the ES with our newly developed needle electrode was a very convenient method for the selective stimulation of the A fibers, since it was very simple, not requiring any special apparatus, did not cause bleeding or burns and caused minimum uncomfortable feeling.
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A prospective investigation of the effects of abuse on future pain and disability was conducted in order to understand better the possible causal role of abuse. Participants were 422 females from a previous population study (Pain 73 (1997) 47-53) who either reported no spinal pain (n=194) or some spinal pain (n=228) at the baseline. A standardized questionnaire was used to assess self-reported physical and sexual abuse during childhood and as an adult. ⋯ This unique prospective study with individuals from the general population underscores the probable importance of abuse in the etiology of a pain or disability problem. Nevertheless, since no clear relationship between abuse and pain was shown for those already reporting pain at baseline, the role of abuse in the development of persistent pain is still not comprehensible. There is a need for investigations with prospective designs employing patients as well as nonpatients as subject.