LiCl-induced flavor avoidance compared between rats and mice using a nondeprivation protocol

Abstract

The present studies examine some parameters involved in flavor avoidance learning, using LiCl to induce malaise, in a novel nondeprivation protocol that allows direct comparison between rats and mice. The procedure involves daily presentation of a gelatin dessert that contains carbohydrate (Polycose) and a distinctive food flavor. Regular chow is additionally available at all times. Both rats and mice showed robust intakes of these gels with little change of gram intake as concentration of Polycose was varied in the range 2-30%; at the highest concentration, the caloric yield was approximately 7% of normal daily intake in both species. Rats that were injected on three occasions with LiCl (0.75 meq/kg) 1 h after consumption of a flavored gel formed a complete and sustained conditioned flavor avoidance (CFA). In a two-flavor discrimination protocol, in which a second flavor was followed by injections of saline, rats showed complete avoidance of the LiCl-paired flavor and partial avoidance of the saline-paired flavor. Mice injected on three occasions with LiCl (6 meq/kg) 1 h after intake of a flavored gel formed a partial CFA; a more complete CFA was formed when there was no delay between removal of the flavor and the injection. Using this no-delay protocol, mice, like rats, showed avoidance of a saline-paired flavor in a two-flavor discrimination protocol, and the CFA was strong when the dose of LiCl was reduced to that used in rats (0.75 meq/kg). In comparable protocols, mice thus are able to form complete CFAs using low doses of LiCl that are comparable to CFAs observed in rats, but the interval between flavor and sickness over which associative learning can occur may be shorter in mice.

Genetic and environmental influences on one‐trial conditioned context aversion in mice

“…The underlying basis of the strain differences in Experiment 1 may also result from variations in the response to LiCl—that is the C57BL/6J strain may not be sensitive to the aversiveness of the drug 43,44 . Research on the role of genetic determinants of susceptibility to LiCl‐induced toxicity indicates that there are strain differences 14,34,43–47 . Evaluation of the time to death after a lethal dose of LiCl shows that C57BL/6J mice are 15x more resistant than the most susceptible strain, the 129/ReJ.…”

“… 43 , 44 Research on the role of genetic determinants of susceptibility to LiCl‐induced toxicity indicates that there are strain differences. 14 , 34 , 43 , 44 , 45 , 46 , 47 Evaluation of the time to death after a lethal dose of LiCl shows that C57BL/6J mice are 15x more resistant than the most susceptible strain, the 129/ReJ. Compared to six other strains of mice (129/ReJ, S.W., C3H/S, DBA/2, Balb/c), C57BL/6J also have the highest ability to eliminate Li + from the body, particularly through urination.…”

Conditioned flavor aversion and brain Fos expression following exposure to arsenic

“…5 and 6) in this study provides solid evidence for the early detection of arsenic by the brain. Several CFA studies document that a decreased intake of saccharin on the test day, when this liquid is the only choice presented to the animal (a one-bottle test), may reflect the effect of the drug on overall fluid intake rather than on intake of a specific fluid (Na and Fitts 2001;Rowland et al 2004). For this reason, 2-bottle tests are considered more sensitive than one-bottle tests, since the reduced intake of the non-preferred substance can be compensated by the supplementary intake of the other fluid (Grote and Brown 1971;Phillips et al 1997).…”