Effect of asphyxia on adenylate cyclase activity in cat brain cortex

Effect of 1-5-min asphyxia on adenylate cyclase activity in cat brain cortex is studied. Adenylate cyclase activity is measured in cortex specimens obtained ex vivo after 1, 2.5, and 5 min of asphyxia, and 30 and 60 min of reoxygenation by radioassay. Stimulating effects of norepinephrine and NaF on adenylate cyclase activity are assessed. Five-min asphyxia induces phasic changes in adenylate cyclase activity: on the Ist min basal activity of the enzyme increases by 97%, after 2.5 min it returns to the initial level, and increases again by 55% on the 5th min of asphyxia. On the 30th and 60th min of reoxygenation after 2.5- and 5-min asphyxia, basal adenylate cyclase activity does not differ from the initial activity. The stimulating effect of norepinephrine and NaF on enzyme activity is weakened after 5 min of asphyxia and 30 min of reoxygenation after 2.5- and 5-min asphyxia. Even short-term asphyxia affects adenylate cyclase activity and modifies the mechanisms of adrenergic signal transduction in the brain cortex in response to oxygen deficiency and probably to hypercapnia as well as during the early reoxygenation period.