Effects of Neuropeptides on Brain Function in Humans

Abstract

The endocrine system can be viewed as a communication system between the brain and the body periphery with efferent and afferent pathways of equal importance. This implies that blood-borne hormones, including peptide hormones, can influence brain functions. This review summarizes a series of experiments designed to analyze effects of vasopressin after intravenous and intranasal administration on brain function in human subjects. Brain function was assessed by electroencephalographic methods, i.e. recording of “event-related brain potentials” and the sleep EEG. Vasopressin was shown to improve signs of attention and cognitive functions, but only with intranasal administration. Intranasal administration of peptides turned out to be a principal way to bypass the blood-brain barrier. Acute intranasal administration of vasopressin failed to restore impaired cognitive functions in elderly human subjects. However, with long-term intranasal vasopressin treatment, sleep disturbancies characteristic of aged people, were ameliorated. Time spent in slow-wave sleep as well as in rapid-eye-movement sleep substantially increased during a 3-month treatment period. Analyzing the actions of neuropeptides on brain function in humans could provide the basis for developing a new, specific, and “soft” neuropharmocology.