Neuroscience letters
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Neuroscience letters · Oct 2005
Intracisternal administration of mitogen-activated protein kinase inhibitors reduced IL-1beta-induced mirror-image mechanical allodynia in the orofacial area of rats.
The present study investigated the role of central mitogen-activated protein kinases (MAPKs) in interleukin-1beta (IL-1beta)-induced mirror-image mechanical allodynia in the orofacial area. Experiments were carried out on Sprague-Dawley rats. Under pentobarbital sodium anesthesia, a polyethylene tube was implanted in the subcutaneous area of one vibrissa pad, which enabled us to inject IL-1beta. ⋯ Intracisternal pretreatment with PD98059, a p44/42 MAPK inhibitor, or SB203580, a p38 MAPK inhibitor, significantly reduced the decrease in the threshold of air puffs ipsilateral to the IL-1beta injection site produced by 10 pg of IL-1beta. IL-1beta-induced mirror-image mechanical allodynia was also reduced significantly by intracisternal pretreatment with both PD98059 and SB203580. These results indicate that central MAPK pathways mediate IL-1beta-induced mirror-image mechanical allodynia in the orofacial area.
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Neuroscience letters · Oct 2005
Lack of interaction between orexinergic and alpha2-adrenergic neuronal systems in rat cerebrocortical slices.
Orexinergic and norepinephrinergic alpha2-adrenoceptor expressing neurons contribute to the regulation of the sleep-wakefulness cycle. In the present study, we have examined a possible interaction between orexinergic and alpha2-adrenergic systems in orexin-A (100 nM)- and K+ (25 mM)-evoked norepinephrine release from slices of rat cerebrocortex. In this tissue norepinephrinergic neurons are predominantly innervated via the locus coeruleus. ⋯ SB-334867 concentration-dependently inhibited orexin A-evoked norepinephrine release with pIC50 (Imax) of 6.05+/-0.14 (86.4+/-5.4%); clonidine (alpha2-agonist) was ineffective. In contrast, yohimbine reversed the inhibitory effects of clonidine (1 microM) on K+-evoked norepinephrine release with pIC50 (Imax) of 6.50+/-0.34 (77.6+/-10.9%); orexin A was ineffective. The present data suggest a lack of interaction between orexinergic and alpha2-adrenergic neurons in rat cerebral cortex.
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Neuroscience letters · Oct 2005
Increased levels of Homer1b/c and Shank1a in the post-synaptic density of spinal dorsal horn neurons are associated with neuropathic pain in rats.
Activity-dependent plasticity in the spinal dorsal horn may underlie the development of neuropathic pain following peripheral nerve injury. In this study we examined whether the expression and loss of behavioral signs of neuropathic pain were associated with changes in the content of the scaffolding proteins Homer and Shank in the post-synaptic density (PSD) of the spinal dorsal horn. In animals exhibiting thermal hyperalgesia and differential weight-bearing behavior 7 days after loose ligation of the sciatic nerve the levels of Homer1b/c and Shank1a were significantly greater than in control, uninjured or sham-operated animals. ⋯ In contrast, there were no differences in the PSD content of Homer1b/c and Shank1a in the dorsal horn of control or sham-operated animals and ligated animals in which the thermal hyperalgesia and differential weight-bearing behavior had disappeared 28 days after the loose ligation. These data revealed a close association between the expression and loss of allodynia and hyperalgesia with changes in the levels of Homer1b/c and Shank1a in the spinal dorsal horn. The reversible shift in the content of scaffolding proteins in the PSD may have important implications for the development of injury-elicited neuropathic pain.
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Neuroscience letters · Oct 2005
Double stimulation of tiny skin areas in human subjects increases the number of C- and Adelta-fiber responses.
The stimulation of tiny skin areas has been shown to be a useful method for the investigation of the central nervous processing of C-fiber stimulation. However, recent studies have also indicated that most subjects fail to recognize a large number of such stimulation. This fact renders this method to be rather time consuming, a fact that limits its applicability. ⋯ This increase of the number of recognized stimuli is accompanied by an increase of the averaged subjects' experience of stimulus intensity. However, there was no significant increase of intensity rating for the different types of fibers stimulated. Data indicate that the double stimulation of tiny skin areas represents an alternative option to the application of single stimuli to tiny skin areas that significantly reduces the exposure time of subjects in order to evaluate behavioral consequences of the stimulation as well as central nervous processing of C- and Adelta-fiber input.
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Neuroscience letters · Oct 2005
Effect of propofol anesthesia on pallidal neuronal discharges in generalized dystonia.
We present the results of continuous microelectrode recordings from individual pallidal neurons in patients with idiopathic torsion dystonia under different levels of propofol anesthesia. Neither the estimated plasma concentration of propofol nor the level of consciousness had a consistent effect on abnormally low neuronal firing rates. Our data support the pathophysiological model of a decreased basal ganglia output in dystonia and argue against a possible pharmacological artifact.