Regulation of intakes of water and NaCl solutions in Fischer 344 rats: Contrasts and comparisons between strains

Abstract

We present an overview of the differences in intakes of both water and NaCl between different strains of rat, with emphasis on Fischer 344 (F344) and Sprague-Dawley (SD) strains. Relative to SD, rats of the F344 strain show less spontaneous or secondary drinking both with food present and during food deprivation. The water intake of rats of the F344 strain is strongly inhibited when water is added to their food, but rats of the SD strain show less inhibition and consume excessive amounts of fluid. In studies of primary drinking, induced by treatment with various dipsogens, rats of the F344 strain consumed water in amounts that were generally comparable to those expected from rats of the SD strain, with the exception of reduced intakes in response to either polyethylene glycol-induced hypovolemia or treatment with isoproterenol. The hematocrit ratio, resting plasma renin activity and directly-measured plasma protein concentrations were similar between F344 and SD strains. We also review findings that rats of the F344 strain show no spontaneous preference for dilute NaCl solutions, and show that both a strong preference and a low preference threshold are induced by chronic treatment with ramipril. Other manipulations that induce an appetite for NaCl in the F344 strain are summarized.