Neuropeptides in Alzheimer's disease: from pathophysiological mechanisms to therapeutic opportunities.

Neuropeptides are found throughout the entire nervous system where they can act as neurotransmitter, neuromodulator or neurohormone. In those functions, they play important roles in the regulation of cognition and behavior. In brain disorders like Alzheimer's disease (AD), where abnormal cognition and behavior are observed, the study of neuropeptides is particularly interesting since altered neuropeptides can function as biomarkers or as targets for new medication. In this article neuropeptides with relevance to AD are listed and their influence on cognitive and behavioral disturbances is discussed. Findings from human cerebrospinal fluid and brain tissue, and AD mouse models are described and related to the pathophysiology and symptomatology of the disease. In the past, clinical trials with neuropeptides have often failed due to insufficient delivery to the brain. Therefore, new strategies to target the brain with peptide drugs are also covered.