Second-order conditioning detects unexpressed morphine-induced salt aversion

Abstract

Morphine failed to condition a salt taste aversion at a dose (15 rug/kg) sufficient to produce a robust aversion to a saccharin taste. Indeed, three different concentrations of salt (1%, 1.5%, and 2%) paired with the same morphine dose yielded no direct evidence for conditioned aversion. Yet, when a novel saccharin taste was paired in compound with the previously conditioned salt conditioned stimulus, we found evidence for a conditioning to the saccharin cue alone in three separate experiments. Control groups eliminated alternative accounts such as neophobia and differential exposure to morphine. Combined, these findings indicate that morphine conditioned a salt aversion. Although this aversion was not directly expressed, a second-order conditioning procedure was able to provide a more sensitive index of conditioning.In the conditioned taste aversion preparation, a taste conditioned stimulus (CS) is paired with an illnessinducing unconditioned stimulus (US) such as LiCI or radiation. The use of this preparation by researchers has made important contributions to the fields of animal learning, psychopharmacology, pharmacology, toxicology, and biomedicine.

Conditioning tastant and the acquisition of conditioned taste avoidance to drugs of abuse in DBA/2J mice

“…This outcome is also generally consistent with the notion that two-bottle testing is more sensitive in revealing conditioned flavor aversions (Dragoin et al 1971;Grote and Brown 1971). Other investigators have also noted morphine-induced CTA was expressed to a saccharin flavor but not a salt flavor (Bevins et al 1996). However, morphine-induced CTA was noted after a second-order conditioning manipulation in which morphinesalt parings followed by salt-saccharin parings produce avoidance of saccharin (Bevins et al 1996).…”

“…Other investigators have also noted morphine-induced CTA was expressed to a saccharin flavor but not a salt flavor (Bevins et al 1996). However, morphine-induced CTA was noted after a second-order conditioning manipulation in which morphinesalt parings followed by salt-saccharin parings produce avoidance of saccharin (Bevins et al 1996).…”

Compared with DBA/2J mice, C57BL/6J mice demonstrate greater preference for saccharin and less avoidance of a cocaine-paired saccharin cue.

“…Avoidance of the drug-paired taste cue is affected by many factors including the nature of the taste cue (Bevins, Delzer, & Bardo, 1996; Grigson, 1997), the need state of the animal (Gomez & Grigson, 1999; Grigson et al , 1999), and by the perceived value of the taste cue and the drug reward (Grigson & Freet, 2000). Regarding the perceived value of the taste cue, for example, Lewis rats often are characterized as addiction-prone or reward-preferring compared with Fischer 344 rats.…”

Altering the Motivational Function of Nicotine through Conditioning Processes

“…However, the possibility that the motivational impact of nicotine would change as a function of conditioning history has not been directly assessed. Widely studied phenomena such as second-order conditioning (Bevins, Delzer, & Bardo, 1996; Holland & Rescorla, 1975; Pavlov, 1927), counterconditioning (Brooks, Hale, Nelson, & Bouton, 1995; Lovibond & Dickinson, 1982; Pearce & Dickinson, 1975), and revaluation (Holland & Straub, 1979; Molina, Bannoura, Chotro, McKinzie, Arnold, & Spear, 1996; Yin & Knowlton, 2002) support the idea that a cue paired with a biologically relevant outcome will acquire additional appetitive or aversive properties depending on the nature of the US. Additionally, there are a few scattered but important published reports more directly related to this suggestion.…”