Changes in Brain Extracellular Adenosine (ADOe ) during Acute Hypoxia

During acute (30s.) hypoxia, total brain tissue Ado increases more than two fold (Winn et al, AJP 1981). However, the alteration in extracellular brain adenosine (ADO e ) during acute hypoxia are unclear. Methods : Consequently, we measured changes in cerebral blood flow (CBF) and ADO e in rat cerebral cortex during 30 & 60 s. of hypoxia (10% FIO 2 ) in anesthetized, ventilated, temperature stabilized rats with cranial windows (dura intact). ADO e by measured on‐line by microelectrode biosensors (ADO e – Inosine e ). CBF was measured by laser Doppler and cerebrovascular resistance (CVR) continuously calculated. Results : PaO 2 decreased to 35.8 ± 5.4 mmHg (n=4) & 30.3 ± 7.5 mmHg (n=16) by 30 and 120 s. As indicated in the figure1, we noted changes in ADO e which paralleled the changes in CBF and CVR. Moreover, the increase in ADO e after 60 s. of hypoxia was greater (p<0.005) than after 30 s.Conclusion: ADO e increases rapidly during hypoxia, paralleling the increases in CBF and the decreases in CVR. Moreover, the magnitude of the increment in ADO e reflects the duration of hypoxia. [supported by R01 (NS 21076 NINDS) to HRW]