Neuroscience letters
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Neuroscience letters · Jul 2000
Noxious hot and cold stimulation produce common patterns of brain activation in humans: a functional magnetic resonance imaging study.
We used functional magnetic resonance imaging (fMRI) to determine whether similar brain regions activate during noxious hot and cold stimulation. Six male subjects underwent whole brain fMRI during phasic delivery of noxious hot (46 degrees C) and noxious cold (5 degrees C) stimulation to the dorsum of the left hand. Mid-brain regions activated included thalamus, basal ganglia and insula. ⋯ Most regions activated bilaterally but with stronger activation contralateral to the stimulus. Noxious cold stimulation produced significantly increased volumes of activation compared to noxious heat in prefrontal areas only. Our results suggest a similar network of regions activate common to the perception of pain produced by either noxious hot or cold stimulation.
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Neuroscience letters · Jul 2000
Role of signals from the dorsal root ganglion in neuropathic pain in a rat model.
We examined whether signals from the neuroma or the dorsal root ganglion of the injured segment are critical for the generation of neuropathic pain. To this aim, we used a rat model of peripheral neuropathy made by transecting the inferior and superior caudal trunks at the level between the S1 and S2 spinal nerves under enflurane anesthesia. These animals displayed tail-withdrawal responses to normally innocuous mechanical stimulation applied to the tail with a von Frey hair (2 g). ⋯ Transection of the S1 spinal nerve between the dorsal root ganglion and neuroma did not change the behavioral signs of neuropathic pain. In contrast, S1 dorsal rhizotomy significantly reduced the behavioral signs. The data suggest that signals arising from the dorsal root ganglion cells of the injured segment, but not from the neuroma, are critical for the generation of neuropathic pain in this model.
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Neuroscience letters · Jun 2000
Intracerebroventricular infusion of nerve growth factor induces pain-like response in rats.
New strategies have recently been developed where infusion of neurotrophic factors into the brain can rescue different neuronal populations. However, negative side effects have been observed in clinical trials infusing nerve growth factor (NGF) into the lateral ventricle in man, namely pain. Little is known about pain behavior in animals after intracerebroventricular (i.c.v.) neurotrophic injections. ⋯ The enhanced responses to mechanical and heat, but not to cold, stimulation were significantly reduced by CP-99994, a selective antagonist to tachykinin NK-1 receptors. When NGF was infused into the brain parenchyma (striatum, cortex and septum) no allodynic nor hyperalgesic responses could be detected. These results indicate that in rats i.c.v. but not intraparenchymal infusion of NGF induce mechanical and cold allodynia as well as heat hyperalgesia, which is mediated, at least in part, by activation of NK-1 receptors.
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Neuroscience letters · Jun 2000
Comparative StudyCo-existence of calcium-binding proteins in neurons of the medullary dorsal horn of the rat.
Double immunofluorescence histochemistry for calcium-binding proteins was performed in the caudal subnucleus of the rat spinal trigeminal nucleus; for calbindin D28k (CB) and calretinin (CR), for CB and parvalbumin (PV), and for CB and CR. CB-immunoreactive (-ir) neurons were seen 1.7 times more frequently than CR-ir neurons and 5.5 times more frequently than PV-ir neurons. About 70-90% of these neurons were distributed in substantia gelatinosa. ⋯ Co-existence of CB and PV was indicated in 1.0% of CB-ir and 5.5% of PV-ir neurons. Co-existence of CR and PV was indicated in 1.4% of CR-ir and 5.1% of PV-ir neurons. In these doubly immunostained neurons, 59.5-69.5% were observed in substantia gelatinosa, 5.9-17.8% in the marginal zone, and 12.7-31.0% in the magnocellular part.
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Neuroscience letters · May 2000
Involvement of spinal protein kinase C in induction and maintenance of both persistent spontaneous flinching reflex and contralateral heat hyperalgesia induced by subcutaneous bee venom in the conscious rat.
To further study the roles of spinal protein kinase C (PKC) in induction and maintenance of both the persistent spontaneous nociception and the contralateral heat hyperalgesia induced by subcutaneous (s.c.) bee venom injection, the effects of intrathecal (i.t.) treatment with a PKC inhibitor, chelerythrine chloride (CH), were evaluated in conscious rats. Pre-treatment i.t. with CH at three doses of 0.01, 0.1 and 1 nmol produced a dose-dependent suppressive effect on the flinching reflex with the inhibitory rates of 39, 48 and 59%, respectively, when compared with the pre-saline control group. ⋯ Post-treatment i.t. with the drug at the highest dose used (1 nmol) also resulted in a 35% reversal effect on the established contralateral heat hyperalgesia. The present result suggests that activation of PKC in the spinal cord contributes to the induction and maintenance of both peripherally-dependent persistent spontaneous pain and contralateral heat hyperalgesia which is dependent upon central sensitization.