Somatostatin (SST) is a well-known neuropeptide that is expressed throughout the brain. In the cortex, SST is expressed in a subset of GABAergic neurons and is known as a protein marker of inhibitory interneurons. Recent studies have identified the key functions of SST in modulating cortical circuits in the brain and cognitive function. Furthermore, reduced expression of SST is a hallmark of various neurological disorders, including Alzheimer's disease and depression. In this review, we summarize the current knowledge on SST expression and function in the brain. In particular, we describe the physiological roles of SST-positive interneurons in the cortex. We further describe the causal relationship between pathophysiological changes in SST function and various neurological disorders, such as Alzheimer's disease. Finally, we discuss potential treatments and possibility of novel drug developments for neurological disorders based on the current knowledge on the function of SST and SST analogs in the brain derived from experimental and clinical studies. Neuropeptide: Nerve cell protein may provide treatment options Developing stable analogues of a key neuronal protein and finding ways to deliver them directly to the brain may provide novel treatments for neurological disorders. The neuropeptide somatostatin (SST) is involved in regulating circuits in the brain cortex and maintaining cognitive function. Reduced SST expression is a recognised feature of brain disorders including Alzheimer's disease. Seung-Hee Lee and co-workers at the Korea Advanced Institute of Science and Technology, Daejeon, South Korea, reviewed the role of SST and examined its therapeutic potential. SST deficiency appears to cause the significant memory loss found in Alzheimer's, and there has been some success trialling intravenous injection of SST in patient trials. However, SST is short-lived in the body, limiting its usefulness as a treatment. Stable SST analogues and safe delivery methods could broaden treatment options for multiple brain conditions.