Saccharin aversion learning in male and female laboratory rats

The three experiments reported in the present research demonstrated that male rats acquire stronger saccharin aversion than females. Experiment 1 revealed that male rats were better than females in a single-trial saccharin aversion learning with a lithium chloride injection as the unconditioned stimulus (US), when normalizing saccharin intake data. Experiment 2 replicated this finding. The stronger saccharin aversion learning in male rats was also observed in Experiment 3 with wheel running as the US, assessed by the saccharin-vs.-water choice test conducted after six saccharin-running pairing days. Experiments 2 and 3 also showed that the magnitude of induced nausea, reflected in the kaolin clay ingestion, is equivalent between the sexes. Experiment 4 excluded the possibility that the observed sex difference in saccharin aversion is due to the sex difference in inherent saccharin preference. These results, taken together, suggest that potential factors of the sex difference in rats' conditioned taste aversion could include sex disparities in taste perception, the ability to associate taste with nausea, and/or the expression of association learning.