Rev Neurol France
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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.
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The Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III) published by the American Psychiatric Association in 1980, and now translated in many languages, has raised a great interest in the whole world. It has probably had on psychiatric thinking as important an impact as the Treatise of Psychiatry of E. Kraepelin at the beginning of the century. ⋯ In addition, the flexibility of its structure allows for the incorporation of new empirical results. In spite of many criticisms, either against the general orientation or against specific positions, some of which are presented in the course of this article, it is concluded that the success of the DSM-III results from a trend in psychiatric thinking not confined to the United States. Its controversial nature has stimulated the reappraisal of old concepts, and it can be considered as an important contribution towards a closer integration of psychiatry to medicine.