CONICET | Buscador de Institutos y Recursos Humanos

Rats display taste avoidance (i.e., suppressed consumption) and aversive orofacial reactions (e.g., reduced mouthing) when stimulated with a tastant (conditioned stimulus, CS) previously paired with moderate to high ethanol doses. Emetic properties of ethanol (EtOH) have been suggested as possible mediators in the acquisition of these conditioned taste aversions (CTAs). This experiment was aimed to scrutinize the mechanisms underlying ethanol-mediated CTA in the infant rat. Preweanlings were assessed in terms of consumption and orofacial responsiveness towards a taste CS previously paired with either EtOH or lithium chloride (LiCl), an emetic agent. A preliminary dose-response study determined doses of EtOH and LiCl that yielded equivalent taste avoidance. On postnatal day 13 (PD13) paired pups (P) were intraorally infused with saccharin (7.5 m, 2.5 % of body weight, BW), then immediately given EtOH (2.5 g/kg, i.g.) or LiCl (0.5% of BW, 0.3M, i.p). Unpaired controls (UP) experienced these stimuli in an explicitly unrelated manner. Intake and taste reactivity tests (TRTs) were conducted on PDs 14 and 15. Statistical analyses (ANOVAs) revealed that, regardless of drug treatment, paired pups consumed less saccharin on PD 14 than control animals. Paired pups also showed, independently of whether they had received EtOH or LiCl, heightened conditioned rejection reactions in the TRT. Specifically, when compared with UP controls, P pups given EtOH or LiCl had equivalent increases in grooming, general activity, head shaking and wall climbing, and equivalent reductions in frequency of mouthing movements. No other quantitative or qualitative differences in taste reactivity were observed between paired conditions. On PD 15, aversive conditioned orofacial reactions were still evident in P rats, even when differences in saccharin intake were no longer observed between P and UP conditions. In conclusion, a taste CS experienced in contiguity with postabortive effects of EtOH and LiCl elicited similar patterns of conditioned rejection in preweanlings, even when employing drug doses titrated in their capability to support conditioned taste avoidance. These results suggest that similar mechanisms may underlie CTAs induced by LiCl and a high EtOH dose in preweanling rats.

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