Putative peptide neurotransmitters in human neuropathology: a review of topography and clinical implications.

In Huntington's disease, there is a decrease of the neuropeptides, substance P, enkephalins, and cholecystokinin in the striatonigral system, whereas in Parkinson's disease an increase of substance P is found in the substantia nigra. Several neuropeptides should be involved in Alzheimer's disease: substance P, endorphins, vasopressin, ACTH, somatostatin, vasoactive intestinal peptide, cholecystokinin, neurotensin, delta sleep-inducing peptide. Alterations of substance P, vasoactive intestinal peptide, cholecystokinin, somatostatin, and endorphins may be related to the pathophysiology of schizophrenia. Delta sleep-inducing peptide may interfere in addiction pathology.