Clinical science
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1. Evidence of an adrenergic component of cutaneous hyperalgesia has recently been obtained in animal models of painful peripheral neuropathy. These findings have prompted speculation that an increased density or sensitivity of peripheral alpha-adrenoceptors contributes to sensory abnormalities and chronic neuropathic pain in conditions such as reflex sympathetic dystrophy. ⋯ The mean density of alpha 1-adrenoceptors in the pain-free skin of patients (26.9 grains/1000 microns2) fell midway between receptor density in hyperalgesic skin and in the skin of normal individuals, and did not differ significantly from either. 5. Our findings indicate that alpha 1-adrenoceptors are present in the epidermis, and suggest that their numbers may be increased in the hyperalgesic skin of patients with reflex sympathetic dystrophy. Further studies need to identify the dermal and epidermal cell types that express high densities of alpha 1-adrenoceptors, and to investigate their normal function and role in neuropathic pain.
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Comparative Study
Nitric oxide in streptozotocin-induced diabetes mellitus in rats.
1. The present study was performed to determine the relationship between diabetic glomerular hyperfiltration and nitric oxide as modulated by the chronic administration of L-arginine and/or N-omega-nitro-L-arginine, a known nitric oxide synthase inhibitor in streptozotocin-induced diabetic rats. 2. Normal rats and rats drinking hypertonic glucose (10%) were used as time-controlled groups. ⋯ The nitric oxide synthase inhibitor increased the plasma and urinary glucose concentration in both diabetic and glucose-drinking rats. 5. Our results indicate that diabetic rats are characterized by high plasma concentrations and elevated urinary excretion of nitrite+nitrate, suggesting a state of high nitric oxide production. The vascular response to nitric oxide in diabetic rats may be different at the glomerular and peripheral vascular bed.
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Comparative Study Clinical Trial Controlled Clinical Trial
Effects of dobutamine on the relationship between oxygen consumption and delivery in healthy volunteers: comparison with sodium nitroprusside.
1. Dobutamine has been used to study the relationship between oxygen consumption (VO2) and oxygen delivery (DO2) in critically ill patients, but this has led to concerns that it could consistently increase VO2 in all patients. Although a direct thermogenic effect of the catecholamine has been primarily implicated in this increase in VO2, an increase in blood flow may contribute significantly by increasing the oxygen requirements of the heart and other organs such as the kidney and the liver. ⋯ However, the VO2/DO2 slopes were similar for both substances. Thus, an increase in VO2 is not exclusively observed with catecholamines. Studies of the effects of therapeutic interventions on oxygen-derived variables should report not only changes in VO2 but also VO2/DO2 slopes.