Pain
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Nerve growth factor (NGF) is known to produce hyperalgesia as well as to stimulate synthesis of neuropeptides in dorsal root ganglia (DRG). In the present study, we wanted to determine the effects of local NGF administration and assess to which extent mast cell-dependent factors are mediating NGF responses. Rats received 1 daily unilateral intraplantar injection for 3 days. ⋯ We suggest therefore that NGF-induced local edema was caused by mast cell-derived vasoactive compounds which act together with afferent neuron-derived CGRP to increase vascular permeability. NGF-induced thermal hyperalgesia most likely was caused by an increased sensitivity of peripheral endings of capsaicin sensitive afferents. This effect of NGF was not mediated by products of the cyclooxygenase pathway, and was also observed in mast cell-depleted rats.
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Clinical Trial
Concerning the homology of painful experiences and pain descriptors: a multidimensional scaling analysis.
How is the sensory (or other) experience of pain related to the words used to describe such experiences? Answering this question would not only improve our general understanding of the relationship between the experience of pain and the report of pain, but also would allow one to quantify inaccuracies or idiosyncracies in this regard. A continuous multidimensional scaling model was used to examine the similarity between noxious electrocutaneous stimuli and the words used to describe them. If these two types of stimulus objects were homologous, one would expect that physical and verbal stimuli with the same meaning would be scaled with similar values along a single dimension; if not, the two types of stimuli would be scaled at opposite poles of a dimension which distinguished between them. ⋯ A single dimension in the group stimulus space scaled both physical and verbal stimulus objects from least to greatest intensity. Since this (or any higher) dimension failed to segregate verbal from physical stimuli, the words appear to be homologous with experience. While conclusions are limited to these specific stimuli, results suggest that the INDSCAL model offers a valuable method for exploring the relationship between pain report and pain experience.
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Clinical Trial
Mechanisms of spontaneous tension-type headaches: an analysis of tenderness, pain thresholds and EMG.
Pericranial muscle tenderness, EMG levels and thermal and mechanical pain thresholds were studied in 28 patients with tension-type headache and in 30 healthy controls. Each patient was studied during as well as outside a spontaneous episode of tension-type headache. Outside of headache, muscle tenderness and EMG levels were significantly increased compared to values in controls subjects, while mechanical and thermal pain thresholds were largely normal. ⋯ EMG levels were unchanged during headache. It is concluded that one of the primary sources of pain in tension-type headache may be a local and reversible sensitization of nociceptors in the pericranial muscles. In addition, a segmental central sensitization may contribute to the pain in frequent sufferers of tension-type headache.