Adenine mononucleotides and their metabolites liberated from and applied to isolated tissues of the mammalian brain.

Preincubation with [(14)C] adenine labeled the nucleotide fraction of isolated cerebral tissues, which subsequently released 0.18% of their(14)C content per minute, a proportion increased threefold by electrical excitation. Of the(14)C released, 2-3% was as 5'-adenine nucleotides and about 2% as cyclic adenosine 3∶5-monophosphate (cAMP). Among the 5'-nucleotides AMP greatly preponderated, and ATP and ADP were detected. When added to (unlabeled) incubating neocortical tissue, ATP and AMP yielded adenosine as the major product, with smaller quantities of inosine and hypoxanthine, to effluent fluids. cAMP so added yielded 5'-nucleotides and the other compounds named; adenosine yielded mainly inosine and hypoxanthine. Results from these reactions and others in which theophylline was included led to the conclusion that an appreciable proportion of the effluent [(14)C] adenosine, inosine, and hypoxanthine derived from cAMP.