[Neuropeptides in Alzheimer's disease]

Of approximately 200 peptides that are known to exist in the body, 80 carry out functions as neurotransmitters and about 20 have been linked to Alzheimer's disease (AD).

In this article we review the most salient studies that have been conducted on neuropeptides such as corticotropin-releasing hormone, thyrotropin-releasing hormone, somatostatin, neuropeptide Y, oxytocin, arginine vasopressin, galanin and insulin, as well as the insulin-like growth factors, the glucagon-like peptides, vasoactive intestinal peptide, cholecystokinin, substance P, opioid peptides and the neuropeptide NAP. Although attempts are made to find a causal association with AD, in many cases the findings are contradictory or not very conclusive.

The most notable points could be the reduction in substance P in the cerebral cortex, hippocampus, basal ganglia and cephalospinal fluid; the diminished levels of somatostatin in the same structures except for the basal ganglia; the reduction in the amount of vasopressin except in the temporal lobe; and the increased levels of dynorphin and leucine enkephalin.