CYCLIC AMP/*SECRETl cyclic AMP into push-pull perfusates in freely moving rats.

Cyclic AMP was found in perfusates of push-pull cannula's, chronically placed in the lateral ventricle of freely moving rats. After addition of norepinephrine, dopamine or adenosine to the perfusates the output of cyclic AMP was enhanced, whilst serotonin and histamine were found to be ineffective. The effects of noradrenaline and dopamine on cyclic AMP were found to be mediated by different receptors: haloperidol antagonized only the dopamine response. The effect of norepinephrine was mimicked by isoprenaline, a beta-adrenergic agonist, but was not blocked by propranolol. L-DOPA, given intraperitoneally, increased cyclic AMP levels in the perfusate. We conclude that the release of cyclic AMP into the extracellular medium is a normally occurring phenomenon in brain tissue.