Pain
-
Erythromelalgia is a condition characterized by attacks of red, hot, painful extremities with relief of symptoms by cooling and aggravation by warmth. Although the main emphasis has been on pathophysiological mechanisms related to circulatory changes, recent reports have focused on an involvement of efferent small nerve fibers indicating a neuropathic component. Since the symptoms resemble those described in neuropathic pain, we wanted to investigate the possible affection of afferent nerve fibers. ⋯ Seven patients had brush-evoked allodynia and fourteen had punctate hyperalgesia inside or close to the symptomatic areas in their feet. When comparing the individual results, there is a tendency to clustering of patients in two separate groups; reduced small fiber input/no hyperalgesia and normal thermal thresholds/hyperalgesia. Our results showing an affection of afferent small nerve fibers together with the nature of the symptoms, suggest that the pain experienced by erythromelalgia patients could have a neuropathic component.
-
Comparative Study
Gender differences in pain, coping, and mood in individuals having osteoarthritic knee pain: a within-day analysis.
This study examined gender differences in prospective within-day assessments of pain, pain coping, and mood in men and women having OA, and analyzed gender differences in dynamic relations between pain, mood, and pain coping. A sample of 64 women and 36 men diagnosed as having pain due to osteoarthritis of the knee(s) rated their pain, pain coping, and mood two times each day (once in the afternoon and once in the evening) for 30 days using a booklet format. Two gender differences were found in between person-analyses: women used more problem focused coping than men, and women who catastrophized were less likely than men to report negative mood. ⋯ Third, men were more likely than women to use emotion-focused coping when their mood was more negative. Finally, men were more likely than women to experience an increase in negative mood and a decrease in positive mood in the morning after an evening of increased pain. Taken together, these findings underscore the importance of obtaining multiple daily assessments when studying gender differences in the pain experience.
-
Comparative Study
Maintenance of windup of second pain requires less frequent stimulation in fibromyalgia patients compared to normal controls.
Many chronic pain syndromes, including fibromyalgia (FM), show evidence of central nervous system hyperexcitability related to central sensitization. Windup (WU) of second pain reflects increased excitability of spinal cord neurons that is related to central sensitization. Psychophysical testing can help characterize this important central nervous system phenomenon because of the parallels between electrophysiological WU and WU of second pain. ⋯ Thus, unlike NC subjects, FM subjects showed enhanced second pain during WU-M stimuli at very low stimulus frequencies, indicating central sensitization. Increased WU sensitivity, enhanced WU-M, and increased WU-related aftersensations help account for persistent pain conditions in FM subjects. In addition to WU, WU-M appears to be a useful tool to study mechanisms of pain in patients with characteristics of central sensitization.
-
Comparative Study
Role of TNF-alpha in sensitization of nociceptive dorsal horn neurons induced by application of nucleus pulposus to L5 dorsal root ganglion in rats.
Herniation of the nucleus pulposus (NP) from lumbar intervertebral discs commonly results in radiculopathic pain and paresthesia (sciatica). While traditionally considered the result of mechanical compression of the dorsal root ganglion (DRG) and/or spinal nerve root, recent studies implicate pro-inflammatory mediators released from or evoked by NP, a possibility that was presently investigated. Single-unit recordings were made from L5 wide dynamic range dorsal horn neurons in pentobarbital-anesthetized rats. ⋯ Thermally and mechanically evoked responses were not significantly affected in control rats or those treated with NP + soluble TNF-alpha receptor type 1. These results indicate that sensitization of nociceptive spinal neuronal responses develops quickly following exposure of the DRG to NP, and that TNF-alpha is involved. This electrophysiological model of herniated NP may prove useful in further characterizing the role of inflammatory mediators in hyperalgesia and allodynia resulting from lumbar disc herniation.
-
Comparative Study
Somatostatin modulates the transient receptor potential vanilloid 1 (TRPV1) ion channel.
Activation of peripheral somatostatin receptors (SSTRs) inhibits sensitization of nociceptors, thus having a short term or phasic effect [Pain 90 (2001) 233] as well as maintaining a tonic inhibitory control over nociceptors [J Neurosci 21 (2001) 4042]. The present study provides several lines of evidence that an important mechanism underlying SSTR modulation of nociceptors is regulation of the transient receptor potential vanilloid 1 ion channel (TRPV1, formerly the VR1 receptor). Double labeling of L5 dorsal root ganglion cells demonstrates that approximately 60% of SSTR2a-labeled cells are positive for TRPV1. ⋯ Furthermore, blockade of peripheral SSTRs with c-SOM dramatically enhances CAP-induced behaviors and nociceptor activity, demonstrating SSTR-induced tonic inhibitory modulation of TRPV1. Finally, TRPV1 does not appear to be under tonic opioid receptor control since the opioid antagonist naloxone does not change CAP-induced excitation and does not effect OCT-induced inhibition of CAP responses. These data strongly suggest that SSTRs modulate nociceptors through phasic and tonic regulation of peripheral TRPV1 receptors.