The journal of pain : official journal of the American Pain Society
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Pulsed radiofrequency, in which short bursts of radiofrequency energy are applied to nervous tissue, has been recently described as an alternative technique devoid of nerve injury, a subsequent side effect of thermal lesions created by continuous radiofrequency lesioning. Yet the mechanism of this effect remains unclear. In this study we compared the acute effects of pulsed versus continuous radiofrequency energy on impulse propagation and synaptic transmission in hippocampal slice cultures and on cell survival in cortical cultures. ⋯ In addition, although both continuous radiofrequency and pulsed radiofrequency treatments induced a distance-dependent tissue destruction under the stimulating needle, the effect was more pronounced in the continuous radiofrequency group. These findings suggest that the acute effects of pulsed radiofrequency are more reversible and less destructive in nature than the classic continuous radiofrequency mode, even in normothermal conditions. This model might help elucidate the importance of various parameters for the clinical application of radiofrequency lesioning and might open new horizons for the role of pulsed radiofrequency lesioning in cases of neuropathic pain.
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Comparative Study
Gonadal hormones do not account for sexual dimorphism in vagal modulation of nociception in the rat.
Subdiaphragmatic vagotomy produces a decrease in mechanical nociceptive threshold that is greater in male rats and an enhancement of bradykinin hyperalgesia that is greater in female rats. To examine the role of gonadal hormones in these sex differences, we evaluated the effect of gonadectomy, with or without gonadal hormone replacement, on vagal modulation of nociceptive threshold and bradykinin hyperalgesia by using the Randall-Selitto paw withdrawal test. Gonadectomy (before sexual maturation) plus vagotomy decreased nociceptive threshold in male rats more than either lesion alone, whereas neither lesion nor in combination had an effect on nociceptive threshold in female rats. ⋯ Testosterone replacement in vagotomized males and 17 beta-estradiol in vagotomized females reversed the effect of gonadectomy. Dihydrotestosterone replacement in vagotomized males also reversed the effect of gonadectomy on bradykinin hyperalgesia, although to a lesser degree than testosterone. We conclude that although gonadal hormones and other gonadal-dependent mechanisms influence nociception, they do not account for sexual dimorphism in vagal modulation of mechanical nociceptive threshold or bradykinin hyperalgesia.
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This study measured mechanical sensation and pain thresholds in the cutaneous field overlying the knee joints of rheumatoid arthritis (RA; N = 27) and osteoarthritis (OA; N = 28) patients, compared with age- and weight-matched normal control subjects (Norm; N = 27) by using graded von Frey monofilaments. A visual analog scale (VASpain), cutaneous joint temperature and circumference were measured for subjective ongoing pain and inflammation. ⋯ The highest scores in average mechanical sensation mapped to the same grid region as the lowest scores in average pain thresholds in RA and OA patients. The simultaneous hypoesthesia and allodynia, with paradoxical decrease in sensation and increased pain thresholds may reflect peripheral and central alterations in neuronal responsiveness to mechanical stimulation and suggests activation of a descending inhibitory system.
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Inflammation of a peripheral nerve (neuritis) causes mechanical and thermal hyperalgesia in the region in which the inflamed nerve innervates. We investigated whether peripherally applied norepinephrine (NE) would exacerbate mechanical hyperalgesia in rats with neuritis. After inflammation of the left L5 spinal nerve with complete Freund's adjuvant, the foot withdrawal thresholds to mechanical stimuli applied to the affected hind paw (mechanical thresholds) were decreased significantly, indicating the development of mechanical hyperalgesia. ⋯ The effect of NE on mechanical hyperalgesia was mediated by both peripheral alpha(1)- and alpha(2)-adrenoceptors. Immunohistochemical study of the previously inflamed nerve showed that proinflammatory cytokine tumor necrosis factor immunoreactivity was significantly higher in the rats showing adrenergic sensitivity compared to rats without adrenergic sensitivity. The data thus suggest that peripheral NE, when released in an excessive amount from the sympathetic nervous system, might play an important role in the aggravation of pain in neuritis.
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Comparative Study
Race and chronic pain: A comparative study of young black and white Americans presenting for management.
Chronic pain is a debilitating problem for many Americans. It affects physical, social, and emotional health. This study addresses the potential differential effects of chronic pain cross-culturally in younger Americans. ⋯ They also experience a higher prevalence of self-identified comorbidities, including dizziness, chest pain, and high blood pressure. In conclusion, considerable diminution in the overall physical and emotional health of black Americans 18 to 50 years of age with chronic pain was noted. These data support the need for further study of the chronic pain experiences of racial and ethnicity minority persons.