Pain
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Noxious stimulation of the rat's face evokes intense face grooming with face wash strokes almost exclusively directed to the stimulated area (e.g. Clavelou et al., Neurosci. Lett., 14 (1989) 3263-3270). ⋯ Only formalin-injected rats displayed significantly more face grooming activity directed to the affected infraorbital nerve territory than unstimulated control rats. Non-painful sensory disturbances (especially mineral oil application) induced an initial bout of directed face grooming; this response was transient and short-lasting. These observations suggest that directed face grooming can be used as a sign of unilateral facial pain in freely moving rodents; unilateral non-painful facial sensory disturbances do not lead to intense and persistent directed face grooming.
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A cold plate apparatus was designed to test the responses of unrestrained rats to low temperature stimulation of the plantar aspect of the paw. At plate temperatures of 10 degrees C and 5 degrees C, rats with either chronic constriction injury (CCI) of the sciatic nerve or complete Freund's adjuvant (CFA) induced inflammation of the hindpaw displayed a stereotyped behavior. Brisk lifts of the treated hindpaw were recorded, while no evidence of other nociceptive behaviors could be discerned. ⋯ At 60 days, neither morphine nor naltrexone affected cold-induced paw lifting in CFA rats, suggesting that the neuronal circuit mediating cold hyperalgesia in these animals had become opiate insensitive. In conclusion, the cold plate was found to be a reliable method for detecting abnormal nociceptive behavior even at long intervals after nerve or inflammatory injuries, when responses to other nociceptive stimuli have returned to near normal. The results of pharmacological studies suggest that cold hyperalgesia is in part a consequence of altered sensory processing in the periphery, and that it can be independently modulated by opiate and adrenergic systems.
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Randomized Controlled Trial Clinical Trial
A fitness programme for patients with chronic low back pain: 2-year follow-up of a randomised controlled trial.
The aim of this study was to assess the long-term effect of a supervised fitness programme on patients with chronic low back pain. The design of the study was a single blind randomised controlled trial with follow-up, by postal questionnaire, 2 years after intervention. The Oswestry Low Back Pain Disability Index was used as the outcome measure to assess daily activity affected by back pain. ⋯ Between group comparisons demonstrated a statistically significant difference in disability scores between the treatment and control group (mean difference 5.8, 95% confidence interval 0.3, 11.4 P < 0.04). This study supports the current trend towards a more active treatment approach to low back pain. We have demonstrated clinical effectiveness of a fitness programme 2 years after treatment but this needs to be replicated in a larger study which should include a cost effectiveness analysis, further analysis of objective functional status and a placebo intervention group.
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Styles of catastrophic thinking about pain have been related to an inability to divert attention away from pain. We investigated whether pain catastrophizers displayed high attentional interference during a threatening low-intensity electrocutaneous stimulus (ES). In Experiment 1, 44 undergraduates performed a tone discrimination task whilst experiencing several times an ES on the left or right arms. ⋯ In Experiment 2, threat was induced in 36 undergraduates by informing them that an ES excites pain fibres. Again, catastrophizers had marked interference immediately after onset. The results are discussed in terms of how catastrophizing amplifies somatosensory information and primes fear mechanisms.
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Case Reports
Epileptic seizure associated with intracerebroventricular and intrathecal morphine bolus.
We report on two patients with morphine-related seizures associated with either intrathecal or intracerebroventricular administration. Both patients had a history of malignant tumor and both experienced the seizures following bolus application of morphine, while even higher dosages were well tolerated when continuously infused. ⋯ Initiation of intrathecal morphine therapy and bolus application should be performed carefully and only when constant monitoring is provided for at least 12 h. Animal data and possible mechanisms for morphine-related seizures are discussed.