Sodium appetite: species and strain differences and role of renin-angiotensin-aldosterone system

The characteristics of the appetite for NaCl in humans differ in some aspects from those in other species. The mechanisms of appetite for NaCl have been studied in detail in two species, rats and sheep. We review the treatments known to induce an appetite for NaCl in rats, with special reference to differences among strains in their spontaneous preference for NaCl solution. The current view of the mechanism is critically appraised, with particular emphasis on the role of angiotensin II, mineralocorticoids, cerebroventricular sodium transport, and the relation between preference for NaCl and the concentration of sodium in saliva. The appetite for NaCl in rodents other than rats is considered next, and reveals that mice, hamsters and gerbils are reluctant to ingest NaCl either spontaneously or after treatment with several of the natriorexigenic stimuli that are effective in rats. The characteristics of the appetite for NaCl in non-rodent species, including sheep, rabbit, dog, and non-human primates, are then described. We discuss some of the possible differences in mechanism that might account for this behavioral diversity among species.