Some critical factors involved in formation of conditioned taste aversion to sodium chloride in rats

Some factors concerning acquisition and retention of conditioned taste aversions (CTAs) were behaviorally examined in the rat. In the CTA paradigm, aqueous solution of 0.1 M NaCl was used as the conditioned stimulus (CS) and an intraperitoneal (i.p.) injection of 0.15 M LiCl was employed as the unconditioned stimulus (US). In experiment 1, CTAs to 0.1 M NaCl were examined in both forward (CS-US) and backward (US-CS) conditioning paradigms. Reliable CTAs were produced in the US-CS conditioning paradigm when the US-CS interval was less than 10 min, as well as in the CS-US conditioning paradigm. In experiment 2, strong CTAs to 0.1 M NaCl were established when water-deprived rats made at least 500 continuous licks, corresponding to 2.5 ml intake and 2 min of drinking time. In experiment 3, effects of gustatory deafferentation on CTA formation were studied. Only the chorda tympani played an important role in acquisition and retention of CTAs to NaCl solutions. These results indicate that strong CTAs can be acquired to 0.1 M NaCl, if its taste information which is conveyed via the chorda tympani during the 500 continuous licks is followed by LiCl-induced sickness.