Ontogeny of preference and aversion to salt in Fischer 344 rats and Syrian hamsters

Fischer 344 (F344) rats and Syrian hamsters, unlike rats of the Sprague-Dawley or Wistar strains, exhibit an aversion to dilute NaCl solutions as adults. In the present studies, using the anterior intraoral infusion method, it is shown that both F344 rats and hamsters accept more dilute NaCl than either water or concentrated NaCl (i.e., show a "single bottle" preference/aversion function identical to Sprague-Dawley rats) at both 6 and 18 days of age. At 18 days of age, they also show a preference for dilute NaCl over water in a simultaneous choice paradigm. In contrast, only 1-3 days later when these animals are weaned, they strongly reject NaCl solutions from sipper tubes in favor of water. It is unlikely that an abrupt discontinuity in neurosensory development can fully explain this dramatic reversal in salt acceptance.