Modeling the effects of low toxin levels in food on feeding: Dose-dependent reduction of fluid intake by low levels of lithium chloride

• Examined dose related effects of adulterating a sucrose + salt solution with LiCl.
• At low LiCl concentrations rats drink in a dose-dependent manner.
• Results in accordance with threshold regulation tolerance mechanism.

The present study examined the dose related effects of low levels of the toxin, LiCl, on the ingestion of a palatable sucrose plus salt solution. Over five days (acquisition phase) rats were presented with a 0.3 M sucrose solution containing one of the following salt combinations: 0.12 M NaCl (n = 10 negative control group); 0.005 M LiCl + 0.115 NaCl (n = 10); 0.01 M LiCl + 0.11 NaCl (n = 10); 0.015 M LiCl + 0.105 M NaCl (n = 10); 0.02 M LiCl + 0.10 M NaCl (n = 10); and 0.12 M LiCl (n = 8 positive control group). During an extinction phase (5 days), all rats were presented with 0.3 M Sucrose + 0.12 M NaCl solution. Fluid intake levels and number of licks were quantified on each day. At low LiCl concentration levels rats exhibited a dose related reduction in amount consumed and number of licks of the sucrose plus salt solutions. This toxin related suppression of fluid intake and licking rapidly dissipated during the extinction phase. The present findings support the hypothesis that rats use a behavioral tolerance mechanism to regulate their intake of foods containing low levels of toxins.