RESUMEN
OBJECTIVE: Muscle pain differs from skin pain with respect to quality, accuracy of localization, and unpleasantness. This study was conducted to identify the brain regions associated with the affective-motivational component of tonic skin and muscle pain. METHODS: Forty healthy volunteers were investigated in three groups with different F-18 fluorodeoxyglucose PET activation scans. A verbal rating scale (VRS) was used to quantify pain intensity and unpleasantness. One group was investigated during painful infusion of an acidified phosphate buffer (pH 5.2) into either muscle or skin for 30 minutes. Muscle and skin infusions were adjusted to achieve pain intensity rating of VRS = 40. The second group received sham stimulation of muscle and skin by infusion of non-acidified phosphate buffer (pH 7.3 to 7.4, pain intensity = 0). The third group underwent only one PET scan without sensory stimulation. RESULTS: Unpleasantness ratings were higher (VRS 38.3 vs 25.5) during IM compared to intracutaneous stimulation, despite the same pain intensity (VRS = 40). Sham stimulation revealed no pain or unpleasantness. Regional cerebral glucose metabolism during sham stimulation showed similar findings for intracutaneous and IM infusions with significant activations of the bilateral anterior cingulate, bilateral frontal (premotor) cortex, and the ipsilateral parietal operculum. The comparison of pain vs sham stimulation revealed activations of the bilateral insula for IM but not intracutaneous stimulation. The unpleasantness perception in skin and muscle stimulation was positively correlated to the bilateral insular metabolism. CONCLUSION: The data suggest that the insula represents one main structure where the unpleasantness of tonic pain perception is encoded.
Asunto(s)
Corteza Cerebral/diagnóstico por imagen , Corteza Cerebral/metabolismo , Emociones/fisiología , Dolor/diagnóstico por imagen , Dolor/fisiopatología , Ácidos/efectos adversos , Enfermedad Aguda , Adulto , Mapeo Encefálico , Tampones (Química) , Enfermedad Crónica , Femenino , Fluorodesoxiglucosa F18 , Lateralidad Funcional/fisiología , Glucosa/metabolismo , Giro del Cíngulo/diagnóstico por imagen , Giro del Cíngulo/metabolismo , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Músculo Esquelético/inervación , Músculo Esquelético/fisiopatología , Nociceptores/efectos de los fármacos , Nociceptores/fisiología , Dolor/metabolismo , Dimensión del Dolor/métodos , Tomografía de Emisión de Positrones , Valores de Referencia , Piel/inervación , Piel/fisiopatología , Factores de TiempoRESUMEN
For a period of 15 weeks growing rats were fed low fat diets containing equimolar doses of alpha- and gamma-tocopherol (180 and 174 ppm) as well as mixtures of alpha- and gamma-tocopherol (3:1; 1:1; 1:3) without cholesterol or with 1% cholesterol. The influence of these supplements on lipid peroxidation and tocopherol retention in the liver were investigated. The tocopherol status was estimated by measuring the activities of creatine kinase and transaminases (GOT, GPT) in plasma as well as by in vitro hemolysis of erythrocytes. The in vitro hemolysis rate was only lowered by alpha-tocopherol and the mixtures of alpha- and gamma-tocopherol. In response to lipid peroxidation in the liver, alpha-tocopherol was the more efficient antioxidant, whereas gamma-tocopherol was more efficient in the diet. Cholesterol had a lowering effect on lipid peroxidation in vitro and in vivo; cholesterol in combination with alpha-tocopherol had a stabilizing effect on the erythrocyte membrane. Moreover, there was a positive effect of cholesterol on tocopherol retention in the liver. The biological activity of gamma-tocopherol in relation to alpha-tocopherol was calculated according to the test criterium; it ranged from 22 to 100%.