[Biochemistry and pharmacology of vigilance: role of neurotransmitters within the framework of vigilance control]

Abstract

Biochemical, pharmacological and neurophysiological research has produced an ever increasing amount of evidence that a variety of (putative) neurotransmitter (NT) mechanisms is implicated in the gross regulation of the many waking behaviours as well as in the organization of sleep. Yet, few of these experimental findings have yielded information as to the exact--specific and detailed--role played by anyone of these "wet" transmission systems in this whole regulatory and organizational function. Based on a new "Universal Concept of Vigilance" we were led to conclude that the actions and influences of at least some of these humoral transmission instruments are considerably better understood, if they are interpreted as being the main controlling instruments of the many local vigilances--the individual levels of responsiveness in the many behavioral systems that are responsible for the making of the many behavioral components. In this new "model" the noradrenergic, cholinergic, dopaminergic, serotonergic, and, possibly, some traceaminergic ascending (and descending) pathways constitute the Output-Component of a larger, reflex-type Vigilance-Controlling Apparatus (VCA). The NA-, Ach-, and the DA-systems are assumed to upregulate (local) vigilance by enhancing reactivity in the neuronal networks that subserve the organization of said behavioral components. In particular, NA- and Ach-pathways can be assumed to enhance mainly (but not exclusively) vigilance in systems of higher functions, whereas DA-fibers probably handle upregulation of reactivity (i.e. eventually vigilance) in the various motor systems. The efficacy of these various aminergic transmission systems is assumed to be further enhanced by a variety of polypeptidergic agents (e.g. TRH, Vasopressin, 4-10-ACTH, enkephalin). In turn, serotonergic pathways are involved as vigilance-reducing instruments. To explain the production of the, for the various waking activities as well as for the various phases and stages of sleep, proper and characteristic vigilance-profiles one has to assume that the activity of these output-channels is per se controlled by a coordinating central apparatus--the very "center"--of VCA.(ABSTRACT TRUNCATED AT 400 WORDS)