Pain
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Comparative Study
Relationship between sodium channel NaV1.3 expression and neuropathic pain behavior in rats.
A multitude of voltage-gated sodium channel subtypes (NaV1) are expressed in primary sensory neurons where they influence excitability via their role in the generation and propagation of action potentials. Peripheral nerve injury alters the expression of several NaV1subtypes, but among these only NaV1.3 is up-regulated in dorsal root ganglia (DRG) neurons. The increased expression of NaV1.3 implicates this subtype in the development and maintenance of neuropathic pain, but its contribution to neuropathic pain behavior has not been examined. ⋯ We then selectively axotomized a cutaneous nerve (sural) and a muscle nerve (gastrocnemius) in order to identify if NaV1.3 up-regulation is dependent on cutaneous and/or muscle afferent activation and found that the numbers of neurons expressing NaV1.3 was proportional to the magnitude of the injury, but independent of the nature of innervation. These results suggest that NaV1.3 increases in primary sensory neurons that are not directly damaged in response to injury. Thus, although NaV1.3 is up-regulated in a subpopulation of DRG neurons after injury, reduction in the expression of NaV1.3 subtype alone is not sufficient to influence the NaV1-dependent behavioral hypersensitivity associated with nerve injury.
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Questions have been raised about the potential neurotoxicity of the neuraxial use of ketamine although ketamine and its active enantiomer S(+)-ketamine have been used intrathecally and epidurally (caudally) for the management of perioperative pain and in a variety of chronic pain syndromes. Clinical experience following neuraxial administration of S(+)-ketamine has been documented without reference to local central nervous system toxicity following this approach. ⋯ However, postmortem observation of the spinal cord and nerve roots revealed severe histological abnormalities including central chromatolysis, nerve cell shrinkage, neuronophagia, microglial upregulation, and gliosis. Based on our results, neuraxial administration of S (+)-ketamine cannot be recommended for clinical practise before a systematic study of toxicology of neuraxial S(+)-ketamine in animals or humans has been performed.
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Comparative Study
A longitudinal study on the predictive validity of the fear-avoidance model in low back pain.
Recently, fear-avoidance models have been quite influential in understanding the transition from acute to chronic low back pain (LBP). Not only has pain-related fear been found to be associated with disability and increased pain severity, but also treatment focused at reducing pain-related fear has shown to successfully reduce disability levels. In spite of these developments, there is still a lack in well-designed prospective studies examining the role of pain-related fear in acute back pain. ⋯ A backward ordinal regression analysis showed previous LBP history and pain intensity to be the most important predictors of end of study GCPS. Of the fear-avoidance model variables, only negative affect added to this model. Our results do not really support the longitudinal validity of the fear-avoidance model, but they do feed the discussion on the role of pain-related fear in early stages of LBP.
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In this systematic review effectiveness of analgesics for pain after tonsillectomy in children was evaluated and trial methodology of the included studies explored. Databases were searched for randomised, controlled studies on systemic paracetamol, NSAIDs and opioids. Eighty-four studies were evaluated for inclusion. ⋯ Because of highly variable methodology and lack of sensitivity only limited conclusions on clinical efficacy of analgesics investigated can be drawn. No analgesic in single prophylactic dose provided analgesia for day of operation. Further studies are needed to find the optimal analgesic(s) for pain after tonsillectomy in children.
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Comparative Study
Increased nerve growth factor after rat plantar incision contributes to guarding behavior and heat hyperalgesia.
Acutely, nerve growth factor (NGF) exerts profound effects on nociceptive transmission and produces pain and hyperalgesia. In the present study, we sought to determine the tissue levels and role of NGF after a plantar incision. A substantial increase in NGF protein expression occurred in skin 4-h, 1-day and 2-days and 5-days after incision comparing contralateral uninjured skin. ⋯ In conclusion, increased NGF was present in skin after plantar incision. NGF contributes to some incision-induced pain behaviors, guarding and heat hyperalgesia. Anti-NGF did not affect the extent of sensitization of C-fibers observed in vitro.