Conditioned taste aversions: From poisons to pain to drugs of abuse

Abstract

Learning what to eat and what not to eat is fundamental to our well-being, quality of life and survival. In particular, the acquisition of conditioned taste aversions (CTAs) protects all animals (including humans) against ingesting foods that contain poisons or toxins. Counterintuitively, CTAs can also develop in situations where we know with absolute certainty that the food did not cause the subsequent aversive systemic effect. Recent non-human animal research, analyzing palatability shifts, indicates that a wider range of stimuli than traditionally acknowledged can induce CTAs. This article integrates these new findings with a reappraisal of some known characteristics of CTA, and presents a novel conceptual analysis that is broader and more comprehensive than other accounts of CTA learning.

Anesthesia-inducing drugs also induce conditioned taste aversions

“…Contrary to this latter interpretation, we have proposed that the CTA mechanism must be very broadly tuned so that it can defend the internal milieu against a diverse array of poisons and toxins that have very different internal effects. As presented below, this new analysis emphasizes that to account for the CTAs induced by USs that are not considered as traditional poisons, we must acknowledge the important function that taste neophobia has in priming expectations about potential poisoning, a role that has not previously been appreciated (for detailed discussion see Lin et al, 2014, 2017). …”

“…This learned reduction in palatability is termed a conditioned taste aversion (CTA) and is considered to result from the acquisition of a Pavlovian association between the taste of the food (conditioned stimulus or CS) and the aversive post-ingestive consequence (unconditioned stimulus or US; e.g., Garcia, 1989; Garcia, Hankins & Rusiniak, 1974; for reviews see Barker, Best & Domjan, 1977; Braveman & Bronstein, 1985; Reilly & Schachtman, 2009). By conditionally lowering taste palatability, CTA learning protects us from the repeated ingestion of poisonous foods (for reviews see Lin, Arthurs & Reilly, 2014, 2017). …”

Flavor preferences conditioned by nutritive and non-nutritive sweeteners in mice

“…In these mouse studies, however, the conditioned preference was for the position (i.e., left vs. right side of cage) or color (i.e., black vs. white) of sipper tubes rather than for the flavor of solutions (e.g., cherry vs. grape) in sipper tubes. It may be that preferences are more readily conditioned to flavor than non-flavor cues, as has been reported for conditioned taste aversions [23]. In addition, the mouse studies used sucralose rather than saccharin as the non-nutritive sweetener.…”

Lactose malabsorption and taste aversion learning

“…Similarly, we have recently found that anesthesia-inducing drugs (ketamine/xylazine and sodium pentobarbital) can serve as USs to support CTA learning (Lin et al, 2017a). Finally, we have discovered that drugs of abuse (e.g., amphetamine and morphine), at dose that are rewarding in other tasks (i.e., place -preference learning and self-administration tasks [e.g., Cappell & LeBlanc, 1971; Cappell, LeBlanc, & Endrenyi, 1973; Hunt & Amit, 1987; Parker, Limebeer, & Rana, 2009; Schuster & Thompson, 1969]), are capable of supporting CTA acquisition (e.g., Arthurs et al, 2012; Arthurs & Reilly, 2013; Lin, Arthurs, Amodeo & Reilly, 2012; for reviews see Lin et al, 2014, 2017b). All these findings, particularly those with drugs of abuse, are at odds with the conclusions derived from research that employed the taste reactivity test to determine palatability of the taste CS.…”