Abstract

Pairing of a gustatory CS and the visceral US induced by lithium chloride (LiCl) results in reduction of consumption of CS solution. This reduction is termed conditioned taste aversion (CTA). Pre-exposure to CS alone prior to the conditioning disrupts the conditioning (latent inhibition) and so is pre-exposure to US. The US pre-exposure effect is hypothesized to be due to tolerance, habituation, or the associative blocking effect. We studied the dose effect of US pre-exposure on CTA. In 3 experiments, rats were exposed to 10 doses of LiCl before the CTA procedure that consisted of ingesting a saccharin solution (0.1%) followed by injection of a constant dose of LiCl (7.632mg/rat). If the pre-exposure reduced the associability of the US, the CTA should be less. Exp. 1: Pre-exposure to 4 or 8 ml/kg of 0.15M LiCl, 1, 2 or 4 days prior to CTA did not have effect. Exp. 2: Pre-exposure to 0.5, 1, 2, 16, 32 ml/kg 1-day prior disrupted CTA. Exp. 3: Pre-exposure to 1, 16, 20, 32, 40 ml/kg 2-days prior disrupted CTA. Summary: (a) The pre-exposure effect was the same whether the pre-exposure occurred 1 or 2 days prior to conditioning. (b) A clear dose-effect relationship existed. (c) The relation was not monotonic. (d) The lowest preexposure dose, 0.5ml/kg of 0.15M LiCl, not strong enough to induce CTA by itself, was effective. (e) Upon repeated pairing of CS and US, CTA became more pronounced. The results do not support the hypotheses mentioned earlier.