Der Schmerz
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Modern concepts of pain therapy involve neuronal mechanisms of endogenous analgesia. Recent animal experiments have provided new insights into the anatomy, physiology and neurobiology of endogenous antinociception. We have shown that antinociception can be maximally activated by disinhibition-and not by direct electrical or chemical excitation-in the midbrain periaqueductal grey matter. ⋯ The high order in the discharges of these neurons is maintained, at least in part, by tonically active descending systems. Thus, the spinal shock syndrome seen in some species after acute spinalisation may result from the loss of order in spinal neuronal discharges normally provided by the brain. The use of modern methods in studies of the functional neuroanatomy, neurophysiology and neurobiology of endogenous antinociception may help in the achievement of better application of results from basic sciences to clinically relevant pain problems.
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The quantitative approach to the study of descending inhibition of spinal nociceptive transmission was initiated in Heidelberg through the use of natural, noxious stimulation and examination of the modulation of the encoding properties of spinal dorsal horn neurons. This important approach required control of the noxious stimulus, which had previously been inadequately considered, and the parametric assessment of modulatory influences on the encoding properties of spinal dorsal horn neurons. As a consequence, descending inhibition of spinal nociceptive transmission was found not to be homogeneous throughout the brainstem, but rather to be significantly different from different brainstem nuclei. ⋯ Most recently, the same approach has been profitably applied to studies that have focused onfacilitatory influences descending from many of the same brainstem sites. As a consequence, it has been proposed that there exists an endogenous pain facilitating system analogous to the well-accepted endogenous pain inhibitory system. While the function of the facilitatory system remains unknown, it is proposed that it may be important to long-lasting pain conditions that exist in the absence of pathology.
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Prolonged administration of morphine for the treatment of chronic pain causes constipation requiring the use of laxatives, which may result in electrolyte deficits. Morphine-induced constipation is due to the binding of the drug to opioid receptors in the gastrointestinal tract and the brain, where it mimics the actions of enkephalins. The effect on the gastrointestinal tract seems to be more intense than the central effect. ⋯ Provided that the anatomical organization of the haemorrhoidal veins in the rat is similar to that in man, slow-release naloxone will be carried by the matrix, to which it is absorbed further down in the gastrointestinal tract. It may thus even reach the rectum, from where, after having been absorbed, it bypasses the liver, enters the central nervous system and reduces the antinociceptive effect of morphine. In conclusion, it can be stated that oral administration of naloxone in combination with morphine may help to prevent constipation during the treatment of chronic pain.
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Anxieties and emotional disturbances associated with cancer often cause pain therapy to be unsuccessful. When psychological support is required it is mostly aimed at supporting cancer patients in attempts to cope with their disease so as to improve the efficiency of pain therapy. In our study we focused on the barriers to cancer pain management that lie in patient's beliefs about pain and their coping behavior. ⋯ Those patients who used cognitive coping strategies and did not communicate often received inadequate pain therapy. Those who talked about pain but did not use any other coping strategies were mostly well treated. We have designed a brochure, "What tumour patients should know about pain" directly oriented on the above pain beliefs; this is now being evaluated with reference to its educational effect.
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In contrast to pain from the skin, muscle pain is often referred to regions remote from the lesion. For instance, trigger points in neck muscles can elicit pain in the head. The convergence-projection theory of Ruch is still the central concept for the explanation of pain referral. ⋯ Therefore, the present paper presents another mechanism, which consists in acute changes in dorsal horn synaptic connections following nociceptive input from muscle. Results from animal experiments indicate that dorsal horn neurons possess ineffective synaptic connections with the body periphery, which become effective under the influence of a painful stimulus and lead to a mislocalization of pain. The neuropeptide substance P is probably involved in the changes in functional organization that occur in the dorsal horn during muscle pain and its referral.