The role of adenosine in the anoxic survival of the epaulette shark, Hemiscyllium ocellatum

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Title The role of adenosine in the anoxic survival of the epaulette shark, Hemiscyllium ocellatum
Author Renshaw, Gillian Mary Claire; Kerrisk, Christopher B.; Nilsson, Goran E.
Journal Name Comparative Biochemistry and Physiology Part B
Editor Thomas P. Mommsen, Patrick J. Walsh
Year Published 2002
Place of publication New York
Publisher Elsevier
Abstract The epaulette shark (Hemiscyllium ocellatum) is among the few vertebrates that can tolerate extreme hypoxia for prolonged periods and, as shown here, anoxia. We examined how anoxia affected this shark's level of responsiveness, concentration of brain ATP and adenosine  an endogenous neuronal depressant. In addition, we investigated how these variables were affected by aminophylline, an adenosine receptor antagonist. Epaulette sharks placed in an anoxic environment (<0.02 mg O2 l1) lost their righting reflex after 46.3±2.8 min, but immediately regained vigilance upon return to normoxia. Then 24 h later, the same sharks were injected with either saline or aminophylline (30 mg kg1) in saline and re-exposed to anoxia. In this second anoxic episode, controls sharks showed a 56% decrease in the time taken to lose their righting reflex but maintained their brain ATP levels; conversely, aminophylline-treated epaulette sharks displayed a 46% increase in the time to loss of righting reflex and had significantly lower brain ATP levels. Since anoxia also caused a 3.5-fold increase in brain adenosine levels, these results suggest that adenosine receptor activation had a pre-emptive role in maintaining brain ATP levels during anoxia. Perhaps because adenosine receptor activation initiates metabolic depression, indicated by the early loss of responsiveness (righting reflex), such a mechanism would serve to reduce ATP consumption and maintain brain ATP levels.
Peer Reviewed Yes
Published Yes
Publisher URI http://www.elsevier.com/wps/find/journaldescription.cws_home/525465/description#description
Copyright Statement Copyright 2002 Elsevier : Reproduced in accordance with the copyright policy of the publisher : This journal is available online - use hypertext links.
Volume 131
Page from 133
Page to 141
ISSN 1096-4959
Date Accessioned 2003-04-29
Language en_AU
Research Centre Heart Foundation Research Centre; Griffith Health Institute
Faculty Griffith Health Faculty
Subject Central Nervous System; Science & Technology
URI http://hdl.handle.net/10072/6802
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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