Pain
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Comparative Study
The Val158Met polymorphism of the human catechol-O-methyltransferase (COMT) gene may influence morphine requirements in cancer pain patients.
Catechol-O-methyltransferase (COMT) inactivates dopamine, epinephrine and norepinephrine in the nervous system. A common functional polymorphism (Val158Met) leads to a three- to-four-fold variation in the COMT enzyme activity, the Met form displaying lower enzymatic activity. The Val158Met polymorphism affects pain perception, and subjects with the Met/Met genotype have the most pronounced response to experimental pain. ⋯ Patients with the Val/Val genotype (n=44) needed more morphine (155+/-160 mg/24 h) when compared to the Val/Met (117+/-100 mg/24 h; n=96) and the Met/Met genotype (95+/-99 mg/24 h; n=67) groups (P=0.025). This difference was not explained by other factors such as duration of morphine treatment, performance status, time since diagnosis, perceived pain intensity, adverse symptoms, or time until death. These results suggest that genetic variation in the COMT gene may contribute to variability in the efficacy of morphine in cancer pain treatment.
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Comparative Study
Enhancement of NMDA receptor phosphorylation of the spinal dorsal horn and nucleus gracilis neurons in neuropathic rats.
NR1 is an essential component of functional NMDA receptors and can be activated by phosphorylation. It is suggested that phosphorylation of NR1 (pNR1) contributes to central sensitization after intradermal capsaicin injection. The present study investigates whether increases of spinal pNR1 are correlated to central sensitization and thus pain behaviors in neuropathic pain. ⋯ A protein kinase A inhibitor, H89, moderately reversed mechanical allodynia in 7 day neuropathic rats. Many pNR1-immunoreactive neurons were identified as projection neurons by retrograde tracer. The data suggest that PKA mediated NMDA receptor phosphorylation plays an important role in spinal nerve ligation induced neuropathic pain.
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Comparative Study
Muscle fiber conduction velocity of the upper trapezius muscle during dynamic contraction of the upper limb in patients with chronic neck pain.
The purpose of this study was to compare average muscle fiber conduction velocity (CV) and its changes over time in the upper trapezius muscle during a repetitive upper limb task in people with chronic neck pain and in healthy controls. Surface EMG signals were detected bilaterally from the upper trapezius muscle of 19 patients and nine healthy controls using linear adhesive arrays of four electrodes. Subjects were asked to tap their hands in a cyclic manner between targets positioned mid-thigh and 120 degrees of shoulder flexion, to the beat of a metronome set at 88 beats/min for up to 5 min. ⋯ Furthermore, the exercise-induced decrease in CV over time was enhanced in the patient group (P<0.05). It was concluded that membrane muscle fiber properties of the upper trapezius and their changes over time during dynamic contraction of the upper limb are different in a sample of people with chronic neck pain with respect to controls. This may be associated with the histological and morphological changes, which have previously been identified in people with pain over the trapezius muscle.
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Trial methodology was evaluated in paediatric analgesic studies. Databases were searched for randomised, placebo controlled studies of systemic paracetamol, NSAIDs and opioids administered for acute postoperative pain in children. Eighty-three studies met the inclusion criteria and 40 were included for the analysis. ⋯ Most patients in the placebo groups had pain that was greater than 30% of the maximum. In conclusion, analysis of the methodology showed several aspects of trial design that can be improved in future studies. Placebo control groups can be used in paediatric analgesic studies to demonstrate internal sensitivity.