European journal of pain : EJP
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Protease-activated receptor-2 (PAR-2) is a G-protein-coupled receptor activated through proteolytic cleavage. It is localized on epithelial, endothelial and inflammatory cells, as well as on transient receptor potential vanilloid 1 (TRPV1) receptor-expressing neurones. It plays an important role in inflammatory/nociceptive processes. ⋯ The inactive peptide, LRGILS-NH(2), injected into either site did not induce any inflammatory or nociceptive changes. These data provide evidence for a significant role of TRPV1 receptors in secondary mechanical hyperalgesia/allodynia and spontaneous pain induced by PAR-2 receptor activation in the knee joint. Although intraplantar PAR-2 activation-induced oedema is also TRPV1 receptor-mediated, primary mechanical hyperalgesia, impaired weight distribution and IL-1beta production are independent of this channel.
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Chronic muscle pain of the neck, shoulder and low back is quite common and often related to a stressed condition. In this study we tried to make a model of long-lasting muscle mechanical hyperalgesia based on one type of stress, repeated cold stress (RCS) (Kita T, Hata T, Yoneda R, Okage T. Stress state caused by alternation of rhythm in environmental temperature, and the functional disorders in mice and rats. ⋯ Bilateral cutaneous punctuate hyperalgesia was also observed with RCS at -3 degrees C. Intramuscular injection of lidocaine confirmed that the muscle was hyperalgesic. RCS might serve as a useful model for study of the mechanism of chronic muscle pain and its treatment.
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Randomized Controlled Trial
Differential physiological effects during tonic painful hand immersion tests using hot and ice water.
The cold pressor test (CPT) is an empirically validated test commonly used in research on stress, pain and cardiovascular reactivity. Surprisingly, the equivalent test with water heated to noxious temperatures (hot water immersion test, HIT) has not been thoroughly investigated. The aim of the present study was to characterize the physiological effects and psychophysics of both tests and to analyze whether the autonomic responses are mainly induced by baroreflexes or a consequence of the pain experience itself. ⋯ Both tests were comparable with regard to the time course and intensity of subjective pain. However, a significantly higher increase of blood pressure could be observed during the CPT when compared to the HIT. The HIT appears less confounded with thermoregulatory baroreflex activity and therefore seems to be a more appropriate model for tonic pain.
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While human infants can display distinctive behavioural and physiological spinal cord and brainstem responses to noxious stimulation, it is not known whether cortical neurons are specifically activated by noxious stimuli in newborns. Here, using a novel approach to time-lock an EEG recording to a clinically required heel lance, we show the presence of a distinct nociceptive-specific potential in newborn infants (35-39 weeks postmenstrual age). ⋯ The magnitude of the nociceptive-specific potential is not dependent on sleep state, whereas an earlier potential (N150-P260-N430), which is sleep-state dependent, is evoked by both noxious and non-noxious stimulation. These results provide the first direct evidence of specific noxious-evoked neural activity in the infant brain and suggest that newborn infants are capable of the sensory-discriminative aspects of pain experience.
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It is important to understand the processes that contribute to disability and distress in adolescents with chronic pain. For example, research has identified that when adolescents can positively adapt to the consequences of health condition, rather than attempt to change the condition itself, they also function better and experience less distress. This pattern of behavior is similar to what is referred to as "acceptance" of pain in the adult literature. ⋯ Regression analyses were carried out to assess the independent contribution of acceptance after pain intensity and demographic variables were taken into account. In these analyses acceptance accounted for significant variance in disability, psychological distress, and developmental and family functioning. We discuss developmental aspects of acceptance in adolescents and clinical implications of these findings.