Abstract— The effect of hypothermia upon cerebral metabolic rate for oxygen (CMRO2) was studied in artificially ventilated rats, anaesthetized with nitrous oxide. Cerebral blood flow was measured with a modification of the Kety and Schmidt technique using 133xenon. CMRO2, was found to decrease linearily with temperature in the temperature range 37°C‐22°C. At normal temperatures CMRO2, fell by about 5 per cent per degree C. At a body temperature of 22°C both cerebral blood flow and CMRO2, were reduced to about 25 per cent of normal.

1 The pharmacology and mRNA expression of endothelin (ET) receptors in human omental arteries were characterized by use of functional contractile assays and the reverse transcriptase-polymerase chain reaction (RT-PCR). 2 In freshly obtained segments of human omental arteries, ET-1 and ET-3 induced concentrationdependent contractions which were normalized to the response produced by 60 mM K+. ET 4 Two-site analysis of the ET-1 induced concentration-response curve from cultured arteries suggests that ETB receptors, at the high potency component, and ETA receptors, at the low potency component, contribute both to the contractile response in relative proportion of 70% and 30%, respectively. Further analysis suggested that the ETA receptor would be capable of evoking at least 75% of the ET-1 contraction in the absence of ETB receptors, although with a lower potency as compared to fresh arteries.5 Electrophoresis of RT-PCR products from the smooth muscle layer of freshly obtained human arteries indicated the presence of mRNA for both ETA and ETB receptors. Arteries cultured for 1 and 5 days demonstrated an increase of mRNA for the ETB receptor as compared to the ETA receptor. The identities of the PCR products were verified by restriction enzyme digestion. 6 In freshly obtained human omental arteries, the contractile effects of endothelins appear to be mediated predominantly by the ETA receptor subtype, with a negligible contribution by ETB receptors. Cultured arterial segments, however, exhibited a substantial ETB receptor mediated contractile response and an increase in ETB receptor mRNA content, consistent with an upregulation of functional ETB receptors. These in vitro data suggest plasticity in the smooth muscle cell expression of contractile ETB receptors.

EKLOF, B., N. A. LASSEN, L. NILSSON, K. NORBERG, B. K. SIESJO and P. TORLOF.Regional cerebral bloodjaw in the rat measured by the tissue sampling technique; a critical evaluation using four indicators CL4-antipyrine, CL4-ethanol, H3-water and xenon133.

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PANNIER, J. L. and I. LEUSEN, Circulation to the brain of the rat, during acute and prolonged respiratory changes in the acid-base balance. PJugers Arch. ges. Physwl. 1973. 338. 347-359. REIVICH, M., J. JEHLE, L. SOKOLOFF and S. S. KETY, Measurements of regional cerebral blood flow with antipyrine-'4C in awake cats. 3. appl. Physiol. 1969. 27. 296 -300. THEYE, R. A. and J. D. MICHENFELDER, The effect of nitrous oxide on canine cerebral metabolism.