HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 586/11/2807    most recent jphysiol.2008.151449v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Larsen, T. S. Articles by Nielsen, H. B. PubMed PubMed Citation Articles by Larsen, T. S. Articles by Nielsen, H. B. Related Collections Integrative Related Article

¹ Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Denmark

Intense exercise decreases the cerebral metabolic ratio of oxygen to carbohydrates [O₂/(glucose + lactate)], but whether this ratio is influenced by adrenergic stimulation is not known. In eight males, incremental cycle ergometry increased arterial lactate to 15.3 ± 4.2 mM (mean ± S.D.) and the arterial–jugular venous (a–v) difference from –0.02 ± 0.03 mM at rest to 1.0 ± 0.5 mM (P < 0.05). The a–v difference for glucose increased from 0.7 ± 0.3 to 0.9 ± 0.1 mM (P < 0.05) at exhaustion and the cerebral metabolic ratio decreased from 5.5 ± 1.4 to 3.0 ± 0.3 (P < 0.01). Administration of a non-selective β-adrenergic (β₁ + β₂) receptor antagonist (propranolol) reduced heart rate (69 ± 8 to 58 ± 6 beats min^–1) and exercise capacity (239 ± 42 to 209 ± 31 W; P < 0.05) with arterial lactate reaching 9.4 ± 3.6 mM. During exercise with propranolol, the increase in a–v lactate difference (to 0.5 ± 0.5 mM; P < 0.05) was attenuated and the a–v glucose difference and the cerebral metabolic ratio remained at levels similar to those at rest. Together with the previous finding that the cerebral metabolic ratio is unaffected during exercise with administration of the β₁-receptor antagonist metropolol, the present results suggest that the cerebral metabolic ratio decreases in response to a β₂-receptor mechanism.

(Received 22 January 2008; accepted after revision 7 April 2008; first published online 10 April 2008)
Corresponding author T. S. Larsen: Department of Anaesthesia, Rigshospitalet 2041, Blegdamsvej 9, DK 2100, Copenhagen Ø, Denmark. Email: tseifert78{at}gmail.com

Related Article

Lactate: a major and crucial player in normal function of both muscle and brain

Avital Schurr
J. Physiol. 2008 586: 2665-2666. [Full Text] [PDF]

This article has been cited by other articles:

				A. Schurr Lactate: a major and crucial player in normal function of both muscle and brain J. Physiol., June 1, 2008; 586(11): 2665 - 2666. [Full Text] [PDF]