Pain
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Identifying individual differences in pain is an important topic; however, little is known regarding patterns of responses across various experimental pain modalities. This study evaluated subgroups emerging from multiple experimental pain measures. One hundred and eighty-eight individuals (59.0% female) completed several psychological instruments and underwent ischemic, pressure, and thermal pain assessments. ⋯ Cluster membership was associated with demographic variables of ethnicity and sex as well as specific psychosocial variables, although cluster differences were only partially explained by such factors. These analyses revealed that groups respond differently across varied pain stimuli, and this was not related solely to demographic or psychosocial factors. These findings highlight the need for future investigation to identify patterns of responses across different pain modalities in order to more accurately characterize individual differences in responses to experimental pain.
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Comparative Study
Comparative actions of the opioid analgesics morphine, methadone and codeine in rat models of peripheral and central neuropathic pain.
Controversy persists in relation to the analgesic efficacy of opioids in neuropathic pain. In the present study the effects of acute, subcutaneous administration of the mu-opioid receptor agonists morphine, methadone and codeine were examined in rat models of peripheral and central neuropathic pain. In the spared nerve injury (SNI) and chronic constriction injury (CCI) models of peripheral neuropathic pain, both morphine (6mg/kg) and methadone (3mg/kg) attenuated mechanical allodynia, mechanical hyperalgesia and cold allodynia for up to 1.5h post-injection (P<0.05); codeine (30mg/kg) minimally alleviated mechanical hypersensitivity in SNI, but not CCI rats. ⋯ The therapeutic window (based on antiallodynia versus ataxia) obtained for codeine, was vastly superior to that obtained with morphine or methadone in SNI and SCI rats. Furthermore, the therapeutic window for codeine in SCI rats was 4-fold greater than in SNI rats. Our results further support the efficacy of mu-opioid receptor agonists in alleviating signs of neuropathic pain in animal models of peripheral and especially central nerve injury.
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Comparative Study
Predictive validity of the Chronic Pain Coping Inventory in subacute low back pain.
The Chronic Pain Coping Inventory (CPCI) was developed to assess eight behavioral coping strategies hypothesized to be important for pain adaptation. But the predictive validity of the CPCI has yet to be tested in a longitudinal study. Here, 321 workers on sick leave after a work accident affecting the low back pain (LBP) region completed the CPCI during the subacute stage (T1) of LBP as well as the Catastrophizing scale of the Coping Strategies Questionnaire (CSQ). ⋯ Catastrophizing and Guarding were the most strongly associated with depressive mood at T1 but at T2, only depressive mood at T1 predicted this same variable. Results indicated also that the Guarding and Catastrophizing scales were able to predict future work status. The present study clearly reveals the usefulness of Guarding from the CPCI and Catastrophizing from the CSQ, when predicting different outcomes of adjustment to low back pain.
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Comparative Study
The Fear of Pain Questionnaire (FPQ): further psychometric examination in a non-clinical sample.
The present study sought to examine psychometric properties of the Fear of Pain Questionnaire (FPQ), a measure of pain-related fear, in a sample of undergraduates. Confirmatory factor analysis confirmed the previously reported three-factor model of the FPQ (e.g. severe pain, minor pain, medical pain), but some items may be redundant. With respect to the reliability of the FPQ, both the FPQ and the subscales showed good internal consistency and test-retest stability was moderate to good. ⋯ Moreover, modest correlation coefficients were found between the FPQ and other pain-related measures. Finally, the minor pain subscale of the FPQ accounted for pain intensity scores on the ischemic pain test and the remaining subscales and the FPQ total scores accounted for pain tolerance on the electrical stimulation test and the thermal pain test. Results are discussed and directions for future research are provided.
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Comparative Study Clinical Trial
Lack of sex differences in modulation of experimental intraoral pain by diffuse noxious inhibitory controls (DNIC).
The aims of this study were to investigate possible sex differences in (a) intraoral pain evoked by topical application of capsaicin to the gingiva, and (b) the modulation of this pain by diffuse noxious inhibitory controls (DNIC). Three groups with a total of fifty-four healthy volunteers (20 men, 20 women using oral contraceptives (W+OC), 14 women not using (W-OC)) completed the study. In two sessions, intraoral pain was evoked by topical application of 30microL 5% capsaicin to the gingiva. ⋯ The degree of modulation by DNIC did not differ between groups (P=0.636). In conclusion, for a superficial type of intraoral pain, only minor sex differences were found in pain intensity and no differences in the degree of endogenous modulation by DNIC. Female sex and the use of OC may not consistently be associated with higher sensitivity to pain.