Neuropeptide Y (NPY) shortens sleep latency but does not suppress ACTH and cortisol in depressed patients and normal controls

Preclinical and clinical studies suggest that neuropeptide Y (NPY) exerts functional corticotropin-releasing hormone (CRH) antagonistic effects. NPY activity appears to be blunted in depression. Recently, we have found in young normal male controls after repetitive administration of NPY a shortened sleep latency and a decrease of time awake and, in the second half of the night, EEG delta-power; cortisol and ACTH levels were blunted. Since during depression there is an overactivity of CRH, we tested the capacity of NPY to affect sleep endocrine activity in patients with depression compared with controls. After one night of adaptation we administered hourly IV injections of placebo (PL) during the second night and of 50 microg NPY during the third night between 22:00 and 01:00 h. Throughout the night ACTH, cortisol and prolactin levels were measured, simultaneously the sleep electroencephalogram (EEG) was recorded. Depressed patients as well as healthy controls exhibited significant shortening of sleep onset latency (SOL) (mean+/-SD; controls: 41.9+/-48.2 min PL vs 22.1+/-17.3 min NPY; patients: 31.8+/-19.8 min PL vs 24.7+/-20.1 min NPY; P