Volume Receptors and the Stimulation of Water Intake

Abstract

It is now well established that loss of volume from the intracellular compartment and loss of volume from the extracellular compartment represent primary and independent stimuli to cerebral mechanisms which initiate drinking and secretion of arginine vasopressin (AVP). Chapter 5 is devoted to a discussion of receptors and mechanisms which stimulate thirst in response to loss of intracellular fluid (ICF) volume. The purpose of this chapter is to examine the receptors which stimulate thirst in response to a deficit in extracellular fluid (ECF) volume. The ECF is composed of interstitial and plasma compartments. As there are no known receptors monitoring the interstitial fluid volume per se the mechanisms considered here are limited to those which respond to changes in vascular volume. Thus, the terms hypo- and hypervolaemia will be used to indicate decreases and increases, respectively, in relation to normal circulating blood volume. The first aim of this chapter is to consider the evidence for and the relative importance of signals arising from peripheral cardiovascular receptors and the renal renin-angiotensin system in drinking caused by hypovolaemia. The second aim is to consider interactions between volume stimuli and osmotic stimuli arising from dehydration as this is a natural event and, in the world outside the laboratory, probably a frequent occurrence. A limited selection of references is given.