Dimensions of "unidimensional" ratings of pain and emotions in patients with chronic musculoskeletal pain.

The use of unidimensional scales to measure pain intensity has been criticised because of the multidimensional nature of pain. We conducted multiple linear regression analyses to determine which dimensions of pain--sensory versus affective--predicted scores on unidimensional scales measuring pain intensity and emotions in 109 Italian women suffering from chronic, non-malignant musculoskeletal pain. We then compared the results with earlier findings in two groups of cancer patients suffering from acute post-operative pain and chronic cancer-related pain, respectively. Age, physical capacity and scores on the multidimensional affect and pain survey (MAPS) were used to predict patients' ratings on one visual analogue scale (VAS) and three numerical rating scales (NRS) measuring pain intensity, anxiety and depressed mood. Unidimensional pain intensity ratings were predicted better from sensory than from affective pain predictors, and the affective predictors made no unique contribution (NRS), or only a very small one (VAS). Both sensory and emotional pain aspects were unique predictors of NRS anxiety and depression. Therefore, in contrast to earlier findings in two different types of cancer patients, in subjects affected by chronic non-malignant musculoskeletal pain, the scores on unidimensional pain intensity scales mainly reflect sensory pain dimensions, supporting the discriminant validity of the NRS and VAS used. However, the patients had some difficulty in distinguishing between sensory and emotional information. For this reason, several unidimensional scales to rate pain intensity and emotions separately should be used to obtain a complete picture of the status and needs of any given patient.

Suggestions of altered balance: Possible equivalence of imagery and perception.

Hypnotic suggestions describing an altered perception induce congruent changes in the subject's experience and behavior. However, it is not known whether an implicit suggestion, only indirectly referring to an altered perception, induces a behavioral response corresponding to that of the real situation. In this study, an implicit suggestion of backward falling (IMP) was given to high hypnotizable participants not exposed (W-Highs) and exposed (H-Highs) to a hypnotic induction and a group of low hypnotizable individuals (W-Lows). Their posture was evaluated through an elite system. The results after the IMP were compared with those after an explicit suggestion of backward falling (EXP). In both W-Highs and H-Highs, the IMP elicited the backward body sway expected in the corresponding real situation, whereas no response was found in W-Lows. The results are discussed in terms of a possible equivalence of imagery and perception or of a lack of the motor inhibition normally associated with motor imagery.

Exposure to the estrogenic pollutant bisphenol A affects pain behavior induced by subcutaneous formalin injection in male and female rats.

We investigated the effects of perinatally administered bisphenol A (BPA), an environmental contaminant with estrogenic activity, on formalin-induced nociceptive responses. Male and female offspring of mother rats treated with BPA or oil were cross-fostered after birth to obtain three homogeneous groups: BPA-prenatal, receiving BPA via the placenta; BPA-postnatal, receiving BPA through suckling; OIL, control, from mothers receiving only peanut oil (vehicle). All groups underwent a pain test with s.c. formalin injection (50 microl, 10%) or were sham injected (pricking with a syringe needle) in the dorsal hind paw. They were immediately placed in an open field apparatus where pain responses (licking, flexing and paw-jerk) were recorded for 60 min. Corticosterone, testosterone and estradiol serum levels were determined in blood obtained at the end of the experiment. BPA-prenatal treatment induced an increase in licking duration in females and in flexing duration in both sexes in the first half of the test (0-30 min after formalin injection). BPA-postnatal treatment induced a decrease in paw-jerk frequency in males and females during the second part of the test (30-60 min after formalin injection). Plasma concentrations of corticosterone, estradiol and testosterone did not differ significantly between groups. These results indicate that exposure to BPA modified the activity of neural pathways and/or centers involved in nociception and pain in a sex-related and exposure-related manner.