Articles: pain.
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Ann. N. Y. Acad. Sci. · Jan 1986
ReviewAltered pain and visual sensitivity in humans: the effects of acute and chronic stress.
In the runner study, as measured by tourniquet ischemic pain, exercise stress produced hypoalgesia 20 minutes post-run, followed by hyperalgesia and euphoria at 30 minutes. The hypoalgesia and euphoria were reversed by naloxone. Exercise stress also produced a decrease in P(A), suggesting hypoalgesia to the thermal cutaneous stimulation. ⋯ Again, in contrast to the acute experimental pain studies, the emotional stress of mental illness produces hypoalgesia, but not anesthesia. Finally, the somatosensory system is not the only the sensory system affected by stress. Cold-pressor pain decreases visual sensitivity both during and for a few minutes following stimulation, and does not interfere with short-term (supra-digit span) memory.
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Review Comparative Study
[Role of the ventrobasal complex of the thalamus in nociception and pain: data obtained in the normal rat and in a model of clinical pain].
Recent anatomical, electrophysiological, neuropharmacological and behavioural studies have provided new elements for the understanding of the role of the thalamus in nociceptive and pain mechanism. Data presented here demonstrate that the thalamic ventrobasal complex (VB), which receives direct afferents from the spinothalamic tract in the rat and monkey, plays a role in the sensory-discriminatory component of pain in these two species. Apart from the electrophysiological aspect, we discuss the effects of analgesic compounds on neuronal responses observed at this level and modifications in a nociceptive reaction threshold after lesions of this structure in the non-anesthetized freely moving animal. ⋯ Spinal tracts transmitting messages from these joints appear to differ (at least in part) from those transmitting nociceptive messages in the normal rat. Finally, at similar doses, morphine is much more effective in these animals than in the normal rat. Results of these studies show that nociception and clinical pain are not always exactly dependent on the same systems.
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Due to the combination of multidisciplinary studies, the last fifteen years have seen a major step forward in our knowledge of nociception. At the peripheral level the role of A delta and C polymodal cutaneous nociceptors is relatively well demonstrated in animal as well as in man. The activation of these nociceptors probably results from both direct effects of the stimulus and indirect effects, mediated by the release of various chemicals. ⋯ Descending influences are exerted from the periaqueductal gray matter and the ventromedial medulla (mainly the nucleus raphe magnus). They are sustained by serotoninergic and noradrenergic mechanisms and they involve to a lesser extent the endogenous opioids. The physiological function of these descending systems is still sharply discussed.