Cerebral oxidative metabolism was studied in vivo by monitoring redox shifts of cytochrome c oxidase in response to direct electrical stimulation of the cerebral cortex in Fischer-344 rats at 3 and 28 months of age. Such activation results in a transient oxidation of cytochrome oxidase associated with brief increase in local cerebral blood volume. In aged rats, the rates of the transient redox responses of cytochrome oxidase (i.e. initial oxidation followed by re-reduction) are slowed by about 50% in comparison to young rats. Cortical norepinephrine was similar in both age-groups. However, while depletion of cortical norepinephrine causes slowing of the rate of re-reduction in young rats by about 50%, such depletion had no effect on the already slow kinetics of the redox shifts of aged rats. Vascular reactivity to increased metabolic demands, defined by the amplitude ratio of the blood volume increase to the cytochrome oxidation, is increased with age but attenuated by norepinephrine depletion in both age-groups. These results suggest that: (1) cerebral cortical levels of norepinephrine do not decline with age in the Fischer-344 rat; (2) development of an age-related impairment in the capability of cerebral oxidative metabolism to respond to conditions of heightened metabolic demands; (3) such impairment is not worsened by depletion of cerebral norepinephrine; (4) exaggerated vascular reactivity to increased metabolic requirement in aging indicates decreased provision of oxygen and metabolic substrates, and (5) this vascular reactivity is mediated by central noradrenergic mechanisms.

Keywords:
Rat, Cerebral cortex, Locus ceruleus, Norepinephrine, Cytochrome oxidase, Cerebral oxidative metabolism
This content is only available via PDF.
© 1983 S. Karger AG, Basel
1983
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.