Maintenance diet and the effects of furosemide on hamsters

Experiment 1 indicated that furosemide, a diuretic, was ineffective in causing hamsters to excrete more urinary sodium when they were fed a sodium-replete diet. Neither the experimental nor the control animals showed any appreciable change in urinary sodium concentration when injected while maintained on Purina lab chow. However, experimental animals that were fed a sodium-deficient diet and then were injected with furosemide showed an increase in urinary volume as well as in sodium concentration in comparison with controls. Experiment 2 assessed the effect of furosemide on the hamsters' intake of saline when they were presented with either 0.9% NaCl and water or 2.0% NaCl solution and water. The results indicated that this diuretic increased the animals' intake of 0.9% saline but not of 2.0% NaCl. Ten days after this experiment, the same hamsters were then tested in a situation where they were presented with both 0.9% and 2.0% saline (Experiment 3). When these animals were injected with furosemide, both groups showed increased intake of 2.0% saline but not of 0.9% NaCl. These results indicate that the outcome of two-bottle preference tests is influenced by the combinations upon which the hamster is making the paired comparison. Experiment 4 involved the comparison of the single-stimulus and double-stimulus methods in assessing the effects of furosemide injections on the saline intake of different groups of hamsters. In general, the double-stimulus method appears to be more sensitive in detecting the natriorexigenic effects of furosemide.