Sheng li xue bao : [Acta physiologica Sinica]
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The formalin test is a commonly used animal model of acute and tonic pain. However, the molecular targets of formaldehyde (FA, the main ingredient of the formalin solution) on primary nociceptor cells remain controversial. In this report, the effects of FA on electrophysiologically-identified primary nociceptor cells were evaluated in vitro and the roles of the vanilloid receptor TRPV1 in FA-produced activation of primary nociceptors were also examined at both cellular and behavioral levels. ⋯ Finally, local effects of CPZ were confirmed in the formalin test and it was shown that the formalin-induced paw flinches were strongly suppressed by CPZ in phase 1 but with phase 2 being significantly suppressed only during 25-55 min. It is therefore concluded that FA can directly activate a subpopulation of primary nociceptor cells and the FA-induced AP discharges are likely to contribute mainly to phase 1, but not phase 2 of the formalin-induced nociception. The activation of primary nociceptor cells by FA is likely to be mediated, at least in part, through TRPV1 and/or TRPA1 receptors.
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The aim of the present study was to investigate the effect of polydatin on apoptosis induced by ischemia/reperfusion (I/R) in rat myocardium and to explore the underlying mechanism. Adult male Sprague-Dawley (SD) rats were randomly divided into control, I/R and polydatin (50 mumol/L) groups. ⋯ The results showed: (1) Compared with those in the control group, the number of TUNEL-positive cells and apoptosis rate were increased in I/R group; (2) Compared with that in the I/R group, the number of TUNEL-positive cells was significantly decreased in the polydatin group [(18.1+/-4.0)% vs (35.1+/-5.4)%, P<0.01]; (3) Apoptosis rate assayed by flow cytometry in I/R group was significantly higher than that in polydatin group [(15.43+/-4.55)% vs (8.66+/-3.18)%, P<0.01]; (4) Expression level of Bax protein was higher in I/R group than that in polydatin group (P<0.05), while the level of Bcl-2 protein and Bcl-2/Bax ratio were higher in polydatin group than those in I/R group (P<0.05, P<0.01), respectively. The results obtained suggest that polydatin exerts an inhibitory effect on I/R-induced apoptosis through increasing Bcl-2 protein expression and decreasing Bax protein expression in myocardium of the rat.
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Endoplasmic reticulum stress (ERS) is an adaptive process in response to circumstantial changes, but excessive and/or prolonged ERS can induce cell apoptosis. C/EBP homologous protein (CHOP) is a very important marker participating in ERS-associated cell apoptosis, while the role of the myocyte apoptosis induced by CHOP remains unclear in the development of hypertrophy. The present study aimed to investigate the effect of CHOP-mediated ERS-associated apoptosis on myocardial hypertrophy induced by abdominal aortic constriction in rats. ⋯ Correlation analysis indicated a positive correlation between CHOP and Bax expression (r=0.654, P<0.01), and a negative correlation between CHOP and Bcl-2 expression (r=-0.671, P<0.01). These results suggest that abdominal aortic constriction induces a significant up-regulation in ER molecular chaperones at early stage of post-surgery, indicating that ERS response is activated in the rat heart; while prolonged ERS could lead to myocyte apoptosis, and CHOP-mediated ERS-associated apoptosis may contribute to myocardial hypertrophy. We speculate that cell apoptosis may take part in the regulation of myocardial hypertrophy and heart failure, and determine the progression of decompensated hypertrophy.
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The purpose of this study was to establish a model of trigeminal neuralgia (TN) through an approach from lower edge of cheekbone and to observe the functional changes in the voltage-gated potassium currents in the cultured trigeminal ganglion (TG) neurons. Thirty Sprague-Dawley male rats were divided into two groups, the sham-operated (sham) group and the operated group. The TN model was carried out by using a chronic constriction injury of the infraorbital nerve (ION-CCI) from lower edge of cheekbone. ⋯ Transient outward potassium currents (I(A)) in both operated and non-operated sides of TG neurons from ION-CCI rats were also reduced significantly compared with that in the sham group. The present study provided a new method of ION-CCI. In this model, the decrease of I(A) and I(K) might contribute, at least in part, to the decrease in mechanical pain threshold of whisker pad and the subsequent hyperalgia.
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While the activation of primary somatosensory (SI) cortex during pain perception is consistently reported in functional imaging studies on normal subjects and chronic pain patients, the specific roles of SI, particularly the subregions within SI, in the processing of sensory aspects of pain are still largely unknown. Using optical imaging of intrinsic signal (OIS) and single unit electrophysiology, we studied cortical activation patterns within SI cortex (among Brodmann areas 3a, 3b and 1) and signal amplitude changes to various intensities of non-nociceptive, thermal nociceptive and mechanical nociceptive stimulation of individual distal finerpads in anesthetized squirrel monkeys. We have demonstrated that areas 3a and 1 are preferentially involved in the processing of nociceptive information while areas 3b and 1 are preferentially activated in the processing of non-nociceptive (touch) information. ⋯ Signal amplitude was enhanced to increasing intensity of mechanical nociceptive stimuli in areas 3a, 3b and 1. Within area 1, nociceptive response co-localizes with the non-nociceptive response. Therefore, we hypothesize that nocicepitve information is area-specifically represented within SI cortex, in which nociceptive inputs are preferentially represented in areas 3a and 1 while non-nociceptive inputs are preferentially represented in areas 3b and 1.