Basic Mechanisms of Opioids’ Effects on Eating and Drinking

Abstract

As far as the relations between brain neurochemistry and behavioral mechanisms of ingestion are concerned, one of the most important hypotheses to emerge concerns endogenous opioidergic peptides and their receptors (see Chapter 3, for details of these endogenous systems). The particular form of the hypothesis considered here is that ingested items provide stimuli which lead to the release of endogenous opioidergic peptides in the central nervous system, which in turn contributes to the maintenance of ingestional behavior. The evidence derives, in the main, from pharmacological experiments using systemically administered agonists and antagonists at opioid-receptors (opioceptors), and from central administration of such drugs and of opioidergic peptides. This chapter does not provide a comprehensive review of a large body of evidence, and deals with experiments using systemically administered drugs in animals. Chapter 6 describes the results of experiments in which drugs have been administered centrally. Several other authors (Chapters 7 & 8) discuss the use of antagonists at opioceptors in human subjects, and consider the potential clinical application of these compounds.