Articles: hyperalgesia.
-
Arch Phys Med Rehabil · Apr 2008
Comparative StudyModulation between high- and low-frequency transcutaneous electric nerve stimulation delays the development of analgesic tolerance in arthritic rats.
To investigate whether repeated administration of modulating frequency transcutaneous electric nerve stimulation (TENS) prevents development of analgesic tolerance. ⋯ These data suggest that repeated administration of modulating frequency TENS leads to a development of opioid tolerance. However, this tolerance effect is delayed by approximately 5 days compared with administration of low- or high-frequency TENS independently. Clinically, we can infer that a treatment schedule of repeated daily TENS administration will result in a tolerance effect. Moreover, modulating low and high frequency TENS seems to produce a better analgesic effect and tolerance is slower to develop.
-
Anesthesia and analgesia · Apr 2008
Antiallodynic and antihyperalgesic effect of milnacipran in mice with spinal nerve ligation.
The antidepressant, milnacipran, has been reported to have antinociceptive, antiallodynic, and antihyperalgesic effects. In this study, we examined the mechanisms of the antiallodynic and antihyperalgesic effects of milnacipran in a model of neuropathic pain induced by spinal nerve ligation in mice. ⋯ We concluded that the antiallodynic and antihyperalgesic effects of milnacipran on neuropathic pain induced by spinal nerve ligation are principally mediated through action at supraspinal and spinal sites via activation of the spinal noradrenergic system.
-
Am. J. Physiol. Gastrointest. Liver Physiol. · Apr 2008
Role for NMDA receptors in visceral nociceptive transmission in the anterior cingulate cortex of viscerally hypersensitive rats.
We have identified colorectal distension (CRD)-responsive neurons in the anterior cingulate cortex (ACC) and demonstrated that persistence of a heightened visceral afferent nociceptive input to the ACC induces ACC sensitization. In the present study, we confirmed that rostral ACC neurons of sensitized rats [induced by chicken egg albumin (EA)] exhibit enhanced spike responses to CRD. Simultaneous in vivo recording and reverse microdialysis of single ACC neurons showed that a low dose of glutamate (50 microM) did not change basal ACC neuronal firing in normal rats but increased ACC neuronal firing in EA rats from 18 +/- 2 to 32 +/- 3.8 impulses/10 s. ⋯ ACC responses to CRD are enhanced in viscerally hypersensitive rats. The enhancement of excitatory glutamatergic transmission in the ACC appears to mediate this response. Furthermore, NMDA receptors mediate ACC synaptic responses after the induction of visceral hypersensitivity.
-
Randomized Controlled Trial
Pharmacological dissection of the paradoxical pain induced by a thermal grill.
We investigated the role of the glutamatergic and endogenous opioidergic systems in the paradoxical pain evoked by the simultaneous application of innocuous warm and cold stimuli to the skin with a "thermal grill". Two parallel randomized, double-blind, cross-over studies, including two groups of 12 healthy volunteers, were carried out to compare the effects of i.v. ketamine or naloxone to those of placebo, on the sensations produced by a thermode (i.e. thermal grill) composed of six bars applied on the palmar surface of the right hand. The temperature of alternate (even- and odd-numbered) bars could be controlled independently by Peltier elements to produce various patterns of the grill. ⋯ By contrast, naloxone had no effect on paradoxical pain, normal pain or non-painful thermal sensations. This study demonstrates for the first time that the "thermal grill illusion of pain" can be modulated pharmacologically. This paradoxical pain, which involves the glutamatergic systems, acting through the NMDA receptors, but not the tonic endogenous opioids systems, might share some mechanisms with pathological pain.