Endogenous Peptides That Inhibit Brain Cyclic AMP Phosphodiesterase

Abstract
Peptide extracts of rat brain powerfully inhibited the cAMP phosphodiesterase activity of rat brain homogenate. Similar extracts of ox brain showed comparable although less potent activity. Preliminary investigation of the physicochemical properties of brain extracts indicated that the rat brain extract contained an active peptide of low MW (about 1400), whereas ox brain contained 2 such peptides (about 1400 and 900). Endogenous oligopeptides that inhibit cAMP phosphodiesterase are apparently present in brain. Experiments on several pure peptides present in the CNS showed that the majority were inactive against brain phosphodiesterase, but ACTH(1-24), somatostatin, substance P and Lys8-vasopressin, in descending order of potency, were active. To help distinguish the peptides found in rat and ox brain extracts from known peptides, preliminary analyses of amino acid composition were performed. The peptides found in brain extracts were apparently distinct from known peptides having the ability to inhibit cAMP phosphodiesterase.