Pain
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The role of operant conditioning for the development and maintenance of chronic pain was examined in 30 chronic back pain patients (CBP) and 30 matched healthy controls. Half of each group was reinforced for increased, half for decreased pain reports while EEG, EOG, heart rate, skin conductance and muscle tension levels were recorded. ⋯ In addition, the CBP group displayed prolonged elevated electromyogram levels to the task. These data suggest that CBP patients are more easily influenced by operant conditioning factors than healthy controls and this susceptibility may add to the maintenance of the chronic pain problem.
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This study examined the impact of pain on self-rated health status in the community-dwelling older adults using the 1993 public release data of the Asset and Health Dynamics Among the Oldest Old (AHEAD). AHEAD is a population-based household survey designed to examine the dynamic interactions between health, family, and economic variables among US older adults. Results showed that 33% of the older adults reported frequent pain and 20% reported significant pain resulting in activity limitation. ⋯ Other predictors (P<0.01) include functional impairment (OR=2.78), chronic diseases (OR=1.89), minority status (OR=1.88), education (OR=1.77), and physician visits (OR=1.64). This study documents the adverse impact of pain on self-rated health as well as the fact that the experience of pain and poor subjective health and well-being is greatest among the most socially disadvantaged older adults (minorities and those with the least education). The findings suggest that treating and controlling pain may significantly enhance the subjective health and well-being of community-dwelling older adults.
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Pain-related somatosensory-evoked potential following CO(2) laser stimulation (laser-evoked potential (LEP)) is now used not only for research objectives, but also for clinical applications. Estimating the conduction velocity (CV) of the spinothalamic tract (STT) by analyzing LEP following activation of Adelta-fibers (Adelta-CVSTT) by CO(2) laser stimulation has been performed previously, but estimating the CV of STT following activation of C-fibers (C-CVSTT) has not. This is the first report to estimate the C-CVSTT in humans; by using the novel method of CO(2) laser stimulation applied to tiny skin areas. ⋯ The nociceptive signal of the C-fibers in STT is probably conveyed by unmyelinated axons of projection neurons to reach the thalamus. Our findings provide the first physiological evidence of the signals ascending through unmyelinated axons in the spinal cord in humans. In addition, estimating C-CVSTT and Adelta-CVSTT combined with conventional methods to measure the CV of the posterior column using electrical stimulation should be useful and have important clinical applications, particularly in patients with spinal cord lesions showing various kinds of sensory disturbances.
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Comparative Study
Analysis of ultrasonic vocalisation does not allow chronic pain to be evaluated in rats.
Most pain tests used for the assessment of drug analgesic activity in animal chronic pain models are based on the measurement of the response to an external acute stimulation (thermal, mechanical or electrical). But these stimuli are not related to the chronic pain experienced by the animal. Quantitative analysis of the spontaneous behaviour induced by the chronic pain state is needed. ⋯ In a third study, the influence of three parameters, degree of confrontation between the rats, age of the conspecific and housing conditions (isolated or collective) was studied in the arthritic rat model. Arthritic rats did not emit more USVs than controls in any of our experimental conditions. A fourth study showed that Aspirin (200 mg/kg) had no effect on the USVs, this data confirms the lack of direct relationship between USVs and experimental chronic pain in rats in our conditions.