Pain
-
It was recently found that nociceptive sensations (stinging, pricking, or burning) can be evoked by cooling or heating the skin to innocuous temperatures (e.g., 29 and 37 degrees C). Here, we show that this low-threshold thermal nociception (LTN) can be traced to sensitive 'spots' in the skin equivalent to classically defined warm spots and cold spots. Because earlier work had shown that LTN is inhibited by simply touching a thermode to the skin, a spatial search procedure was devised that minimized tactile stimulation by sliding small thermodes (16 and 1mm(2)) set to 28 or 36 degrees C slowly across the lubricated skin of the forearm. ⋯ These results provide psychophysical evidence that stimulation from primary afferent fibers with thresholds in the range of warm fibers and cold fibers is relayed to the pain pathway. However, the labile nature of LTN implies that these low-threshold nociceptive inputs are subject to inhibitory controls. The implications of these findings for the roles of putative temperature receptors and nociceptors in innocuous thermoreception and thermal pain are discussed.
-
Facial expressions of pain and emotions provide powerful social signals, which impart information about a person's state. Unfortunately, research on pain and emotion expression has been conducted largely in parallel with few bridges allowing for direct comparison of the expressive displays and their impact on observers. Moreover, although facial expressions are highly dynamic, previous research has relied mainly on static photographs. ⋯ Additional rating data further suggest that, for comparable expression intensity, pain is perceived as more arousing and more unpleasant. This study strongly supports the claim that the facial expression of pain is distinct from the expression of basic emotions. This set of dynamic facial expressions provides unique material to explore the psychological and neurobiological processes underlying the perception of pain expression, its impact on the observer, and its role in the regulation of social behaviour.
-
The present study examined the relation between stage of chronicity and treatment response in patients with work-related musculoskeletal conditions and concurrent depressive symptoms. Also of interest was the role of reductions in pain severity, catastrophic thinking and fear of movement/re-injury as mediators of the relation between chronicity and treatment response. A sample of 80 individuals (38 women, 42 men) with a disabling musculoskeletal pain condition and concurrent depressive symptoms participated in the research. ⋯ The results highlight the importance of early detection and treatment of depressive symptoms, given that treatment response decreases over time. The results also suggest that reductions in depressive symptoms might be a precondition to the effective reduction of pain symptoms in this population. Discussion addresses the factors that might contribute to treatment resistance as the period of disability extends over time.
-
Psychological and social factors have been shown, separately, to predict outcome in individuals with chronic low back pain. Few previous studies, however, have integrated both psychological and social factors, using prospective study of clinic populations of low back pain patients, to identify which are the most important targets for treatment. One hundred and eight patients with chronic low back pain, newly referred to an orthopaedic outpatient clinic, completed assessments of demographic characteristics, details of back pain, measures of anxiety and depression (Hospital Anxiety and Depression Scale, HADS), fearful beliefs about pain (Fear Avoidance Beliefs Questionnaire), social stresses (Life Events and Difficulties Schedule) and physical aspects of health-related quality of life [SF-36 Physical Component summary Score scale (PCS)]. ⋯ Number of healthcare contacts over the 6 months ranged from 1 to 29, and was independently predicted by perceived cause of pain [Incident Rate Ratio (IRR)=1.46, p=0.03], Fear Avoidance Beliefs about work (IRR=1.02, p=0.009) and back pain related social difficulties (IRR=1.16, p=0.03). To conclude, anxiety, depression, fear avoidance beliefs relating to work and back pain related stresses predict impairment in subsequent physical health-related quality of life and number of healthcare contacts. Interventions targeting these psychosocial variables in clinic patients may lead to improved quality of life and healthcare costs.
-
Increased blood pressure and sweet taste are often associated with decreased pain sensitivity. Animal research suggests that endogenous opioids are involved in both these relationships. Fifty-eight healthy young adults (36 male, 22 female) participated in two sessions receiving a placebo tablet or 50mg of naltrexone on counterbalanced days. ⋯ However, the GLM of tolerance also produced a significant drug by DBP interaction suggesting that blood pressure-related analgesia is at least partially opioid-mediated. Also participants with higher DBP showed dampened mood reactivity to the experiment, which was partially reversible by naltrexone. These results are consistent with findings suggesting that endogenous opioid activity may contribute to generally reduced pain sensitivity, and perhaps mood reactivity, in those with higher BP.