Neuroscience letters
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Neuroscience letters · Feb 2011
Comparative StudyDownregulation of GABAB receptors in the spinal cord dorsal horn in diabetic neuropathy.
Diabetic neuropathic pain is a common clinical problem and remains difficult to treat with classic analgesics. Spinal dorsal horn neurons are important in mediating nociceptive signaling, and the hyperactivity of these neurons is critical in diabetic neuropathy. In this study, we determined the GABA(B) receptor expression level in dorsal horn neurons in streptozotocin (STZ)-induced diabetes in rats by using reverse-transcription polymerase chain reaction (RT-PCR) and western blot analyses. ⋯ Furthermore, the protein expression level revealed by western blot analysis was lower in STZ-treated rats than in saline-treated rats. These data suggest that GABA(B) receptors are downregulated in the spinal dorsal horn in this model of STZ-induced diabetic neuropathic pain. The reduction of GABA(B) expression may contribute to the hyperactivity of spinal dorsal horn neurons and diabetic neuropathic pain.
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Neuroscience letters · Feb 2011
NF-κB subunits are differentially distributed in cells of lumbar dorsal root ganglia in naïve and diabetic rats.
Previous studies demonstrated that nuclear factor κB (NF-κB) activation is decreased in dorsal root ganglia (DRG) of rats having streptozotocin (STZ)-induced diabetes. DRG contain cell bodies of neurons that convey sensory signals from the periphery. To determine the relationship between diabetes-induced neuropathy and NF-κB expression in DRG, behavioral, immunohistochemical, and biochemical studies were performed on naïve and 3-month diabetic rats. ⋯ In many cases, prominent staining was also present in nuclei, a location consistent with transcription factor activation. Immunohistochemical and biochemical studies found that the nuclear to cytoplasmic ratio of p50 expression was significantly reduced in diabetic rats compared to that in naïve animals. Our findings raise the possibility that changes in NF-κB activation in a subset of DRG neurons participates in mediating diabetes-induced sensory neuropathy.
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Neuroscience letters · Feb 2011
Neuromagnetic activity in the somatosensory cortices of children with cerebral palsy.
Children with cerebral palsy (CP) have altered tactile, proprioceptive and kinesthetic awareness. These sensory impairments appear to be related to an aberrant organization of the somatosensory cortex. To date, the neuromagnetic responses of somatosensory cortices representing the foot have not been investigated in children with spastic diplegic CP. ⋯ All participants underwent unilateral tibial nerve stimulation of each foot as whole brain MEG data were acquired. Primary somatosensory cortical responses were modeled using an equivalent current dipole for each foot. The results presented in this study are the first to show that activation of the somatosensory cortices representing the foot in children with spastic diplegic CP is diminished, but not latent.
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Neuroscience letters · Feb 2011
Involvement of dorsal hippocampal α1-adrenergic receptors in the effect of WIN55,212-2 on memory retrieval in inhibitory avoidance task.
In the present study, the possible role of α1-adrenergic receptors of the dorsal hippocampus on WIN55,212-2-induced amnesia in male Wistar rats has been evaluated. As a model of learning, a step-down passive avoidance task was used. Results indicated that post-training or pre-test intra-CA1 administration of WIN55,212-2 (0.25 and 0.5 μg/rat) reduced the step-down latency, showing an amnestic response. ⋯ Interestingly, pre-test intra-CA1 administration of α1-noradrenergic agonists, phenylephrine alone or with an ineffective dose of WIN55,212-2 (0.25 μg/rat) reversed post-training WIN55,212-2 (0.5 μg/rat)-induced retrieval impairment. On the other hand, pre-test intra-CA1 microinjection of an α1-adrenergic antagonist, prazosin (0.5 μg/rat), 2 min before administration of WIN55,212-2 (0.5 μg/rat) inhibited the pre-test WIN55,212-2 response. It may be concluded that α1-adrenergic receptors of the dorsal hippocampal CA1 regions play an important role in WIN55,212-2-induced amnesia and restoration of memory by pre-test WIN55,212-2 administration.
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Rapid skin heating by infrared lasers can be used to investigate the integrity of the nociceptive system by activating A-delta and C fibers. The aim of our study was to analyze if healthy humans exhibit any clinically relevant diurnal variations in their heat pain sensitivity. Circadian A-delta fiber function was analyzed by studying N2 and P2 components of laser-evoked potentials (LEP) and pain thresholds evoked by laser stimulation of the foot every 2h from 8a.m. to 10p.m. in 15 healthy subjects. ⋯ Laser-induced heat pain thresholds and circadian latencies of LEP did not significantly vary during the day. Our results correspond with previous studies that did not detect any consistent significant diurnal variations in perception of heat pain perception using contact thermodes. The intensity of pain perception did not demonstrate any correlation with mood or sleep parameters as measured with the Beck Depression Inventory (BDI), the subjective sleep scales Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS).