“Hidden” properties of neuropeptides: Hypnogenic activity of the tripeptide complex DSIP + NPY + ANP

Abstract

To test the hypothesis that certain peptide complexes can cause effects that cannot be exerted by the same peptides when used separately, the effect of a tripeptide combination of delta sleep-inducing peptide (DSIP), neuropeptide tyrosine (NPY), and atrial natriuretic peptide/factor (ANP/ANF) was studied. In accordance with theoretical vector analysis, such a combination should exert a pronounced anxiolytic effect. Conventional polygraph electrodes and a cannula were preliminarily implanted in the lateral ventricles of rabbits. Peptides (individually or in combination) or a saline solution (control), were administered into the lateral brain ventricle (at a volume of 60–80 µl) at the beginning of the 12-h dark period in experimental chambers. Paperless polygraph recording was continued for 24 h. It was discovered that the tripeptide combination drastically increased hypnogenic activity within the first hours of recording, whereas each peptide alone was either ineffective (DSIP and ANP) or less effective (NPY). We suggest that some neuropeptides may possess a “hidden” physiological activity which becomes evident only after their combined administration or endogenous release.