The ontogeny of salt preference in rats

Many mammals eat salt irrespective of need. This behavior, called salt preference or appetite, is studied primarily in adults. Little is known about its ontogeny. In these experiments, 3-18-day-old rat pups were offered saline, quinine, or ammonium chloride solutions by infusion through an anterior oral catheter, and intake was measured. At 6-18 days, pups showed the inverted U-shaped preference-aversion curve for NaCl that is characteristic of adult rats. Thus, rats express a preference for salt at a very early age. However, the curves were broader than the typical adult curve and were shifted along the concentration gradient in an age-related fashion. Consumption of quinine and ammonium chloride showed similar age-related changes. These changes may reflect the postnatal timing of the development of the rat gustatory system.