The application of electrical pulses to slices of guinea pig cerebral cortex led to an increase in the levels of adenosine 3',5'-phosphate (cyclic 3',5'-AMP) of more than 11-fold within 10 min. This effect of electrical pulses was severely reduced in the presence of theophylline. Cyclic 3',5'-AMP accumulation in slices was increased in the presence of norepinephrine and histamine about 1.5-fold and six-fold, respectively; the effect of electrical pulses was augmented in the presence of maximal amounts of either amine. For these and other reasons, the accumulation of cyclic 3',5'-AMP induced by electrical stimulation cannot be ascribed to the release and action of either histamine or norepinephrine.

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