Abstract

Incubation of slices of rabbit cerebral cortex with histamine resulted in large accumulations of adenosine 3',5'-phosphate. Maximal levels of the nucleotide required about 15 min exposure to histamine and represented more than an 8-fold increase. Inclusion of theophylline (0.5 mM) in incubation media had little effect by itself on the accumulation of adenosine 3',5'-phosphate but increased the effect of histamine 3-fold. Norepinephrine increased the nucleotide level only about 70%, but only 2 min exposure to the agent was required to produce maximal values. This pattern of responses is in sharp contrast to that observed in cerebellar slices, but appears to be similar to that of other areas of rabbit brain. The content of adenosine 3',5'-phosphate in the cerebral cortex of rabbit heads frozen rapidly at intervals after decapitation rose about 8-fold within 90 sec after decapitation. Although phosphorylase a levels increased very rapidly after decapitation, no changes in phosphorylase a content of either cerebellar or cerebral cortex slices was detected under conditions producing large increases in adenosine 3',5'-phosphate.