Acta physiologica Scandinavica
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Acta Physiol. Scand. · Oct 1976
Cerebral metabolic state after discontinuation of nitrous oxide supply in artificially ventilated rats.
Previous results from this laboratory have shown that when administration of 70% nitrous oxide is discontinued in artificially ventilated rats, cerebral oxygen uptake increases by about 40% at 5 min and by about 80-90% at 30 min, and that this increase is blocked by previous adrenalectomy. In the present experiments, nitrous oxide was withdrawn for 45 s, 2 min 45 s, or 15 min, in non-adrenalectomized animals, and for 5 min in adrenalectomized animals, and the tissue was frozen in situ for subsequent measurements of labile phosphates, glycolytic metabolites, citric acid cycle intermediates and associated amino acids and ammonia. ⋯ In adrenalectomized animals, discontinuation of nitrous oxide supply did not induce changes in any of the tissue metabolites measured. We conclude that 70% N2O neither influences the metabolic rate of the tissue, nor its metabolic state.
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Acta Physiol. Scand. · Oct 1976
Cerebral utilization of glucose, ketone bodies and oxygen in starving infant rats and the effect of intrauterine growth retardation.
Cerebral arteriovenous differences of acetoacetate, D-beta-hydroxybutyrate, glucose, lactate and oxygen and brain DNA content was measured at 20 days of age in intrauterine growth retarded (IUGR) rats and normal littermates after 48 and 72 h of starvation. Cerebral blood flow (CBF) was measured with labeled microspheres in other comparable groups of IUGR and control rats. CBF was similar in IUGR and normal littermates (0.57+/-0.09 and 0.58+/-0.10 ml/min respectively). ⋯ In IUGR rats these percentage values were 26.5 and 25.7 respectively. After 72 h of starvation the fraction of total cerebral uptake of substrates accounted for by ketone bodies was significantly higher in control that IUGR rats. As total cerebral uptake of substrates was similar between IUGR and control animals it is concluded that IUGR rats are more dependent on glucose as a substrate for the brain during starvation.