Brain research
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It has been suggested that long-term potentiation (LTP) of dorsal horn neurons is a phenomenon that contributes to the development of chronic neuropathic pain. Spinal cord stimulation (SCS) may be an effective tool in alleviating such pain. The aim of this electrophysiological study in rats was to examine if SCS suppresses LTP of dorsal horn wide dynamic range (WDR) neurons. ⋯ Here we report that SCS gradually reduced this increased C-fiber response back to the baseline level. However, A-fiber responses were neither potentiated by the conditioning stimulus used nor were they affected by SCS. These data suggest that SCS affects the C-fiber component of dorsal horn central sensitization which is noteworthy since SCS, based on previous studies, is believed to primarily influence A-fiber functions.
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We have previously shown that colon irritation (CI) in neonates results in chronic visceral hypersensitivity in adult rats, associated with central neuronal sensitization in the absence of identifiable peripheral pathology. The purpose of this study is to assess the relative contribution of peripheral mechanisms to chronic visceral hypersensitivity by examining the changes in responses of primary afferents at thoracolumbar (TL) and lumbosacral (LS) spinal segments to graded colorectal distension (CRD). Afferent discharges were recorded at the cut distal ends of spinal dorsal roots (DRs) in adult control and CI rats. ⋯ In summary, the results show that chronic visceral hypersensitivity is associated with peripheral sensitization, as well as central sensitization. TL visceral afferents projecting seem to be more involved in the processing of sensitized nociceptive input from the colon than acute nociceptive input. However, LS afferents seem to be equally important in both sensitized and acute pain states.
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Ischemic cerebrovascular disease (stroke) is one of the leading causes of death and long-time disability. Ischemia/reperfusion to any organ triggers a complex series of biochemical events, which affect the structure and function of every organelle and subcellular system of the affected cells. The purpose of this study was to investigate the therapeutic efficacy of N-acetyl cysteine (NAC), a precursor of glutathione and a potent antioxidant, to attenuate ischemia/reperfusion injury to brain tissue caused by a focal cerebral ischemia model in rats. ⋯ NAC treatment also blocked the ischemia/reperfusion-induced expression of tumor necrosis factor and inducible nitric oxide synthase. The data suggest that pre-administration of NAC attenuates cerebral ischemia and reperfusion injury in this brain ischemia model. This protective effect may be as a result of suppression of TNF-alpha and iNOS.
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Unilateral T13 hemisection of the rat spinal cord produces a model of chronic spinal cord injury (SCI) that is characterized by bilateral hyperexcitability of lumbar dorsal horn neurons, and behavioral signs of central pain. While we have demonstrated that responsiveness of multireceptive (MR) dorsal horn neurons is dramatically increased at 28 days after injury, the effects of acute hemisection are unknown and predicted to be different than observed chronically. In the present study, the consequences of T13 hemisection are examined acutely at 45 min in MR neurons both ipsilateral and contralateral to the site of injury, and compared to the same class of cells at 28 days after injury (n=20 cells total per group: 2-3 cells/side of the cord from n=5 animals). ⋯ In animals 28 days after hemisection, spontaneous activity of MR neurons was comparable to intact levels ipsilaterally, and cells exhibited hyperexcitability to evoked stimuli bilaterally. Expansion of cutaneous receptive fields was observed only in hindpaws ipsilateral to the lesion, acutely. These results demonstrate dynamic plasticity in properties of dorsal horn somatosensory neurons after SCI.
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The emotional component of nociception is seldom distinguished from pain behavioral testing. The aim of the present study was to develop a behavioral test that indicates the emotional pain responses using the classical conditioning paradigm. The role of the anterior cingulate cortex (ACC) in the process of this pain conditioning response was also evaluated. ⋯ The association between a neutral stimulus and a noxious stimulus could be demonstrated in a Pavlovian conditioning test in free moving rats. Thus, the conditioned response may be employed as a measure of the emotional component of the nociception. It is also suggested that the ACC may play an important role in mediating this conditioning effect.