The American journal of physiology
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The brain has evolved mechanisms for sensing and regulating glucose metabolism. It receives neural inputs from glucosensors in the periphery but also contains neurons that directly sense changes in glucose levels by using glucose as a signal to alter their firing rate. Glucose-responsive (GR) neurons increase and glucose-sensitive (GS) decrease their firing rate when brain glucose levels rise. ⋯ In rats with diet-induced obesity and hyperinsulinemia, GR neurons are hyporesponsive to glucose. Insulin-dependent diabetic rats also have abnormalities of GR neurons and neurotransmitter systems potentially involved in glucose sensing. Thus the challenge for the future is to define the role of brain glucose sensing in the physiological regulation of energy balance and in the pathophysiology of obesity and diabetes.
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Lisofylline [1-(5R-hydroxyhexyl)-3,7-dimethylxanthine] decreases lipid peroxidation in vitro and in vivo suppresses proinflammatory cytokine expression in models of lung injury due to sepsis, blood loss, and oxidative damage. In the present experiments, we used a murine hyperoxia model to examine the effects of lisofylline on the activation of nuclear transcriptional regulatory factors [nuclear factor-kappaB and cAMP response element binding protein (CREB)], the expression of proinflammatory cytokines in the lungs, and the circulating levels of oxidized free fatty acids as well as on hyperoxia-induced lung injury and mortality. ⋯ Lisofylline diminished hyperoxia-associated increases in lung wet-to-dry weight ratios and improved survival in animals exposed to hyperoxia. These results suggest that lisofylline ameliorates hyperoxia-induced lung injury and mortality through inhibiting CREB activation, membrane oxidation, and proinflammatory cytokine expression in the lungs.
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It appears that the expression of vascular endothelial growth factor (VEGF) is increased during brain injury and thus may contribute to disruption of the blood-brain barrier (BBB) during cerebrovascular trauma. The first goal of this study was to determine the effect of VEGF on permeability of the BBB in vivo. The second goal was to determine possible cellular mechanisms by which VEGF increases permeability of the BBB. ⋯ To determine a potential role for nitric oxide and stimulation of soluble guanylate cyclase in VEGF-induced increases in permeability of the BBB and arteriolar dilatation, we examined the effects of NG-monomethyl-L-arginine (L-NMMA; 10 microM) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1.0 microM), respectively. L-NMMA and ODQ inhibited VEGF-induced increases in permeability of the BBB and arteriolar dilatation. The findings of the present study suggest that VEGF, which appears to be increased in brain tissue during cerebrovascular trauma, increases the permeability of the BBB via the synthesis/release of nitric oxide and subsequent activation of soluble guanylate cyclase.
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Activation of spinal opioid receptors contributes to hypotension after hemorrhage in conscious rats.
Opioid receptors are activated during severe hemorrhage, resulting in sympathoinhibition and a profound fall in blood pressure. This study examined the location and subtypes of opioid receptors that might contribute to hypotension after hemorrhage. Intrathecal naloxone methiodide (100 nmol) abolished the fall in blood pressure after hemorrhage (1.5% of body wt; mean arterial pressure 122 +/- 8 mmHg after naloxone methiodide vs. 46 +/- 5 mmHg in controls, P < 0. 001). ⋯ Comparisons of the minimum effective doses of these antagonists in relation to their binding affinities provides strong evidence for the participation of delta-receptors in mediating hypotension after hemorrhage. In contrast, the dose at which nor-BNI was effective suggests an effect at delta-receptors but not kappa-receptors. The efficacy of CTOP, albeit at a high dose, also suggests an effect at mu-receptors.