Pain
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In 144 healthy subjects tonic heat stimuli were applied with a contact thermode and systematically varied with respect to 3 parameters: temperature T, rate of temperature change RTC, and duration D. In addition, the stimulus temperature at which the first sensation of pain occurred was produced by some subjects. In both types of experiments, subjects compared heat intensity felt at the beginning and the end of the stimulus and then set stimulus temperature to correspond with their initial sensation. ⋯ The average skin temperature of the point of transition from adaptation to sensitization was equal to the average pain threshold temperature. The temperature change response maintained individual differences of thermal and pain sensitivity and was highly consistent for each subject. Potential applications of the procedure in clinical and experimental pain research are discussed.
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Recent evidence has underscored the importance of parental models and vicarious learning in the etiology of pain behavior. The present study investigated the relationships between the number of familial pain models to which an individual has been exposed, the individual's reports of current pain experiences, and the role of gender. ⋯ Additionally, pain models had a greater impact on females than on males. These findings are discussed in terms of vicarious learning and health locus of control processes.
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Ketamine is an injectable anesthetic agent that has been shown to interact as an agonist at opiate receptors. In addition, its antinociceptive action in rats is antagonized by the narcotic receptor antagonist naloxone. Thus it was assumed that the anesthetic may activate the pain inhibitory pathway, originating in the periaqueductal gray (PAG) and descending into the spinal cord, in a manner similar to that of narcotics like morphine. ⋯ This action interfered with opiate actions in the PAG and made data from the microinjection studies difficult to interpret. The descending, pain inhibitory neuronal system originating in the PAG does not appear to participate in the antinociceptive action of ketamine measured by the tail-flick reflex. Perhaps the drug's effects are associated with alternative opiate mechanisms and/or opiate receptor subtypes not present on the cells of origin of the descending nerves within the PAG.
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Eighteen patients with chronic musculoskeletal pain completed a trial of EMG feedback where each subject was exposed to biofeedback, a control condition and a waiting list. Pain scores were determined pre- and posttrial, and the percentage change calculated for each subject. EMG activity and present pain measured during the trial gave an EMG/pain correlation for each patient. ⋯ In addition, patients with high EMG/pain correlations had a better outcome and this measure also correlated with pain scores. The relationship between self-concepts and EMG/pain correlations is discussed. The Illness Self-Concept Repertory Grid appears capable of predicting treatment outcome and shows promise as a prognostic tool.