Taste aversion conditioning with heat as an unconditional stimulus: The role of taste intensity and preexposure in rats

High ambient temperature was previously found effective as an unconditional stimulus (US) in a taste aversion procedure using a highly concentrated saccharin solution as the taste conditional stimulus (CS; Davey & Biederman, 1996a). Rats initially showed intense neophobic drinking suppression to the strong saccharin taste but increased consumption markedly over trials in the absence of forward pairings of taste and heat exposure. We interpreted the failure of attenuation of neophobia with forward pairings as evidence of a conditioned taste aversion but noted the alternative hypothesis that heat interferes with memory for the taste. The present paper reports the results of two strategies that directly address this alternative. Pairing a mild saccharin taste with heat exposure minimized neophobia but again produced only relative drinking suppression by comparison with unpaired and unheated controls. Preexposing a strong saccharin taste minimized neophobia and produced a gradual decrease in saccharin consumption over conditioning trials in the forward group. This constitutes the first unique support for heat-induced taste aversion conditioning not susceptible to a neophobia interpretation. (C) 1997 Academic Press.