Articles: hyperalgesia.
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To determine whether the local and referred pain from active myofascial trigger points (MTrPs) reproduce the overall spontaneous fibromyalgia syndrome (FMS) pain pattern and whether widespread pressure hypersensitivity is related to the presence of widespread active MTrPs in FMS. ⋯ The local and referred pain elicited from widespread active MTrPs fully reproduced the overall spontaneous clinical pain area in patients with FMS. Widespread mechanical pain hypersensitivity was related to a greater number of active MTrPs. This study suggests that nociceptive inputs from active MTrPs may contribute to central sensitization in FMS.
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Comparative Study
A peripheral adrenoceptor-mediated sympathetic mechanism can transform stress-induced analgesia into hyperalgesia.
Stress has paradoxical effects on pain, causing stress-induced analgesia but also exacerbating pain via poorly understood mechanisms. Adrenergic neurotransmission is integral in pathways that regulate the response to both pain and stress. Hyperalgesia is often associated with enhanced adrenergic sensitivity of primary afferents, but sympathetic nervous system outflow has not been demonstrated to exacerbate pain perception after stress. ⋯ Sympathetic postganglionic nerves can enhance pain sensation via a peripheral α-1-adrenoceptor mechanism when sympathetic outflow is disinhibited. The net effect of stress on pain sensation reflects a balance between descending spinal inhibition and sympathetic outflow that can shift toward pain facilitation when central and peripheral α-2-adrenoceptor inhibitory mechanisms are attenuated.
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Journal of neurotrauma · Jun 2011
Delayed intrathecal delivery of RhoA siRNA to the contused spinal cord inhibits allodynia, preserves white matter, and increases serotonergic fiber growth.
RhoA is a key regulator of the actin cytoskeleton that is upregulated after spinal cord injury (SCI). We analyzed different methods for siRNA delivery and developed siRNAs targeting RhoA (siRhoA) for SCI treatment. Cy 3.5-labeled siRNA delivered at the time of SCI yielded fluorescence in several cell types in the injury site. ⋯ Histological analysis at 8 weeks showed significant improvement in white matter sparing with siRhoA compared to control siRNA. siRhoA treatment also resulted in less accumulation of ED1+macrophages, increased PKC-γ immunoreactivity in the corticospinal tract rostral to the injury site, and increased serotonergic fiber growth 12 mm caudal to the contusion site. The ability of siRhoA to preserve white matter and promote serotonergic axonal regrowth caudal to the injury site is likely to suppress allodynia. This provides justification for considering clinical development of RhoA inhibitors to treat SCI sub-acutely to reduce allodynia, which occurs frequently in SCI patients.
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Pressure algometry is used for assessment of pain sensitivity. In this study the relation between tissue characteristics and pressure pain thresholds was investigated. ⋯ The pressure pain sensitivity of the deep layer is related to the amount of muscle strain, which is affected by the muscle hardness and the thickness of adipose tissue. This is clinically relevant as these two factors are not taken into consideration when pressure pain assessments are performed in clinical routine.
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Experimental neurology · Jun 2011
Protection against oxaliplatin-induced mechanical hyperalgesia and intraepidermal nerve fiber loss by minocycline.
Treatment with the chemotherapeutic agent oxaliplatin produces a robust painful neuropathy similar to various other neuropathic conditions which result in loss of nerve fibers innervating the skin. This loss of intraepidermal nerve fibers (IENFs) appears to play an important role in neuropathy, but has yet to be investigated in oxaliplatin-induced neuropathic pain. For this study, mechanical hyperalgesia and IENF density were measured in rats receiving oxaliplatin, given at a dosage of 2 mg/kg every other day for four injections. ⋯ Immunohistochemistry using the pan-neuronal marker PGP9.5 was used to investigate IENF densities in hind paw skin on Day 15 and Day 30. The results show that a robust mechanical sensitivity developed in oxaliplatin treated animals, as did a pronounced decrease in epidermal nerve fibers, and these outcomes were effectively prevented by minocycline treatment. This is the first study to show changes in IENF density in oxaliplatin treated animals, and confirm not only a relationship between IENF loss and hypersensitivity but also prevention of both with minocycline treatment.