Neuropeptides and Affective Disorders

Abstract

Pituitary hormones regulate the endocrine organs, are involved in many homeostatic mechanisms in the body, and have direct effects on processes in the central nervous system. The latter was initially demonstrated by animal behavioral experiments¹ and confirmed by neurochemical and electrophysiological studies in animals.² Fragments of pituitary hormones may have similar effects on behavior as the parent hormones, but interestingly they hardly elicit the classical endocrine actions of the parent hormones. The central effects of pituitary hormones and their fragments indicate that they belong to the category of neuropeptides, which are peptide molecules that affect nerve function and/or are present in nerve tissue. Research during the last decade has disclosed that many peptide molecules, including the pituitary hormones, are present in the central nervous system, and that they are presumably located in neuronal pathways. They are synthesized in large proteins, and several are formed in the same molecule. A cascade of processes evolve in peptidergic neurons to express the genetic information into biologically active neuropeptides. These processes control the quantities of neuropeptides synthesized as well as the nature of their biological activity through size, form, and derivation of the endproduct. In this way sets of neuropeptides with different, opposite, and more selective properties are formed from the same precursor.