P. Hylland et al., TIME-COURSE OF ANOXIA-INDUCED INCREASE IN CEREBRAL BLOOD-FLOW RATE INTURTLES - EVIDENCE FOR A ROLE OF ADENOSINE, Journal of cerebral blood flow and metabolism, 14(5), 1994, pp. 877-881
The exceptional ability of the turtle brain to survive prolonged anoxi
a makes it a unique model for studying anoxic survival mechanisms. We
have used epiillumination microscopy to record blood flow rate in venu
les on the cortical surface of turtles (Trachemys scripta). During ano
xia, blood flow rate increased 1.7 times after 45-75 min, whereupon it
fell back, reaching preanoxic values after 115 min of anoxia. Topical
superfusion with adenosine (50 mu M) during normoxia caused a 3.8-fol
d increase in flow rate. Superfusing the brain with the adenosine rece
ptor blocker aminophylline (250 mu M) totally inhibited the effects of
both adenosine and anoxia, while aminophylline had no effect on normo
xic flow rate. None of the treatments affected systemic blood pressure
. These results indicate an initial adenosine-mediated increase in cer
ebral blood flow rate during anoxia, probably representing an emergenc
y response before deep metabolic depression sets in.