A comparison between taste avoidance and conditioned disgust reactions induced by ethanol and lithium chloride in preweanling rats

Abstract

Adult rats display taste avoidance and disgust reactions when stimulated with gustatory stimuli previously paired with aversive agents such as lithium chloride (LiCl). By the second postnatal week of life, preweanling rats also display specific behaviors in response to a tastant conditioned stimulus (CS) that predicts LiCl-induced malaise. The present study compared conditioned disgust reactions induced by LiCl or ethanol (EtOH) in preweanling rats. In Experiment 1 we determined doses of ethanol and LiCl that exert similar levels of conditioned taste avoidance. After having equated drug dosage in terms of conditioned taste avoidance, 13-day-old rats were given a single pairing of a novel taste (saccharin) and either LiCl or ethanol (2.5 g/kg; Experiment 2). Saccharin intake and emission of disgust reactions were assessed 24 and 48 hr after training. Pups given paired presentations of saccharin and the aversive agents (ethanol or LiCl) consumed less saccharin during the first testing day than controls. These pups also showed more aversive behavioral reactions to the gustatory CS than controls. Specifically, increased amounts of grooming, general activity, head shaking, and wall climbing as well as reduced mouthing were observed in response to the CS. Conditioned aversive reactions but not taste avoidance were still evident on the second testing day. In conclusion, a taste CS paired with postabsorptive effects of EtOH and LiCl elicited a similar pattern of conditioned rejection reactions in preweanling rats. These results suggest that similar mechanisms may be underlying CTAs induced by LiCl and a relatively high EtOH dose.

Figure 1

Intake scores during conditioning (PD 13) and extinction sessions (PDs 14 and 15) as a function of the different Conditioning treatments (CS-only, LiCl-1 %, LiCl-0.5 % or EtOH 2.5 g/kg). Vertical lines illustrate standard errors of the means.

Figure 2

Behavior scores of the different reactions registered during the taste reactivity tests (PDs 14 and 15) as a function of Conditioning treatment (paired or unpaired) and Unconditioned stimulus (LiCl or EtOH). Vertical lines illustrate standard errors of the means.

Figure 3

Intake of saccharin as a function of Conditioning treatment (paired or unpaired) and nature of Unconditioned stimulus given to the pups (LiCl or EtOH). Vertical lines illustrate standard errors of the means.