Articles: hyperalgesia.
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Among brain structures receiving efferent projections from the histaminergic tuberomammillary nucleus is the pontine locus coeruleus (LC) involved in descending noradrenergic control of pain. Here we studied whether histamine in the LC is involved in descending regulation of neuropathic hypersensitivity. Peripheral neuropathy was induced by unilateral spinal nerve ligation in the rat with a chronic intracerebral and intrathecal catheter for drug administrations. ⋯ Zolantidine or pyrilamine alone in the LC failed to influence pain behavior, while A-960656 (histamine H3 receptor antagonist) suppressed hypersensitivity. A plausible explanation for these findings is that histamine, due to excitatory action mediated by the histamine H2 receptor on noradrenergic cell bodies, promotes descending spinal α1/2-adrenoceptor-mediated inhibition of neuropathic hypersensitivity. Blocking the autoinhibitory histamine H3 receptor on histaminergic nerve terminals in the LC facilitates release of histamine and thereby, increases descending noradrenergic pain inhibition.
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We report a novel symptom in many patients with low back pain (LBP) that sheds new light on the underlying pain mechanism. By means of quantitative sensory testing, we compared patients with radicular LBP (sciatica), axial LBP (LBP without radiation into the leg), and healthy controls, searching for cutaneous allodynia in response to weak tactile and cooling stimuli on the leg and low back. Most patients with radicular pain (~60%) reported static and dynamic tactile allodynia, as well as cooling allodynia, on the leg, often extending into the foot. ⋯ The presence of central sensitization also provides the first cogent account of shooting pain in sciatica as a wave of activity sweeping vectorially across the width of the sensitized dorsal horn. Finally, the results endorse leg allodynia as a pain biomarker in animal research on LBP, which is commonly used but has not been previously validated. In addition to informing the underlying mechanism of LBP, bedside mapping of allodynia might have practical implications for prognosis and treatment.
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To investigate the role of preoperative pain sensitivity and preoperative symptom severity for prediction of postoperative pain intensity after lumbar spine surgery. ⋯ The study highlights that each preoperative back pain and individual pain sensitivity could predict the different aspects of postoperative pain after lumbar surgery.
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Pharmacol. Biochem. Behav. · Dec 2014
Antihyperalgesic effect of 5-HT7 receptor activation on the midbrain periaqueductal gray in a rat model of neuropathic pain.
The 5-HT7 receptor is the most recently discovered receptor for 5-hydroxytryptamine (5-HT), and only little is known about the analgesic potential of this receptor. Adenosine triphosphate (ATP) modulates pain transmission by activating P2X/P2Y receptors, in which the P2X3 subtype is an important target for this effect. This study examined the antihyperalgesic effect of the 5-HT7 receptors in the ventrolateral midbrain periaqueductal gray (vlPAG), a crucial site for endogenous pain inhibition. ⋯ Furthermore, the antihyperalgesic effect of the 5-HT7 receptor was partially but significantly blocked by A-317491 pretreatment. These data indicate that the 5-HT7 receptor in the vlPAG exerts an antihyperalgesic effect on rats with neuropathic pain. The 5-HT7 and P2X3 receptors interact in the vlPAG and exhibit an analgesic action through the enhanced function of the endogenous analgesic system.
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There is a strong association between migraine and depression. The aim of this study is to identify migraine-specific factors involved in this association. ⋯ This study identified allodynia, in addition to high migraine attack frequency, as a new migraine-specific factor associated with depression.