The effect of morphine preexposure on the acquisition of morphine-induced taste aversions: A nonassociative effect

Abstract

In Experiment 1, the amount of time rats spent engaged in a range of behaviors was recorded immediately prior to and following the intraperitoneal administration of morphine sulfate (6 mglkg) or distilled water. No behavioral differences were observed between these groups. In Experiment 2, preexposure to this low dose of morphine attenuated the subsequent acquisition of a morphine-induced taste aversion independent of the similarity of the preexposure and conditioning environments. These results with a dose of morphine that does not produce any behavioral effects, which in turn could potentially mask associative conditioning during preexposure, confirm that the attenuating effects of morphine preexposure on taste aversion learning are nonassociative.

A history of morphine-induced taste aversion learning fails to affect morphine-induced place preference conditioning in rats

“…First, these demonstrations used LiCl as the conditioning agent, whereas morphine was used in the present series of experiments. Although a history with morphine has been reported to attenuate the subsequent acquisition of morphine-induced taste aversions (see Hunt, Spivak, & Amit, 1985;LeBlanc & Cappell, 1974;Simpson & Riley, 2005), there is little evidence that such attenuating effects are associative in nature; that is, they are reported independent of the similarity of the preexposure and conditioning environments, suggesting that such effects are nonassociative in nature (see Domjan & Siegel, 1983;Riley, Dacanay, & Mastropaolo, 1984;Stewart & Eikelboom, 1978). Second, the specific procedure utilized here is a modified blocking design in which the taste stimulus previously associated with morphine was not given concurrent with the environment in the second phase of the study.…”

The role of injection cues in the production of the morphine preexposure effect in taste aversion learning

“…For example, morphine is one drug of abuse that has been extensively examined in the preexposure design, and preexposure to morphine has been found to consistently attenuate morphine-induced aversions in this preparation (Cappell & LeBlanc, 1977;Dacanay & Riley, 1982;Domjan & Siegel, 1983;Gaiardi et al, 1991;LeBlanc & Cappell, 1974;Riley et al, 1984;Simpson & Riley, 2005). Interestingly, varying the environmental cues from preexposure to conditioning does not disrupt the morphine-induced preexposure effect (Dacanay & Riley, 1982;Stewart & Eikelboom, 1978), suggesting that this effect is not mediated by environmental cues available to the animal during preexposure.…”

“…The present experiments were conducted to determine the role of injection-related cues in the morphine preexposure effect in taste aversion learning (Cappell & LeBlanc, 1977;Dacanay & Riley, 1982;Domjan & Siegel, 1983;Hunt, Spivak, & Amit, 1985;Miller, Kelly, Neiswander, McCoy, & Bardo, 1990;Riley et al, 1984;Simpson & Riley, 2005). In both experiments, subjects received morphine during preexposure, followed by a series of saline injections (to extinguish the association of the injection cues with the effects of morphine) prior to aversion conditioning with morphine.…”

Simple delayed discrimination of tastes in the rat

“…In long-delay taste aversion learning, rats can acquire taste aversions when delays of 8 and 12 h separate ingestion of a specific taste and the administration of a toxin (see Nachman, 1970;Nachman & Jones, 1974;Revusky, 1968;Riley et al, 1984;Riley & Tuck, 1985b;Smith & Roll, 1967;see also Etscom & Stephens, 1973), suggesting an extended memory for tastes within this design. However, because of the many procedural differences between the delayed taste discrimination and taste aversion designs (for example, stimulus amount, duration, and familiarity, degree of interference, number of conditioning trials, and similarity or comparability of the reinforcer) conclusions regarding the basis for the differences in the extent of taste memory, for example, differential processing of the taste stimulus (see Bures & Buresova, 1977;Domjan, 1983Domjan, , 1985; see also Garcia, Rusiniak, Kiefer, & BermudezRattoni, 1982), must await further research.…”