Endogenous neuropeptide, mainly expressed in the cortex and hippocampus, that has structural and functional similarities to somatostatin-14. Displays potency at all somatostatin receptors (sst1 - sst5) and prevents somatostatin-14 binding (IC50 values are 5, 0.09, 0.3, 0.2 and 0.3 nM at sst1, sst2, sst3, sst4 and sst5 receptors respectively). Also binds to the growth hormone secretagog receptor (GHS-R1a). Exhibits neuronal depressant and sleep-modulating properties in vivo.