Heroin-induced suppression of saccharin intake in water-deprived and water-replete rats.

Rats suppress intake of a saccharin conditioned stimulus (CS) when paired with an aversive unconditioned stimulus such as lithium chloride. This phenomenon is referred to as a conditioned taste aversion (CTA). Rats also suppress intake of a saccharin CS when paired with a rewarding sucrose solution and when paired with a drug of abuse. Although the suppressive effects of drugs of abuse have long been interpreted as CTAs, evidence suggests that rats may suppress intake of the saccharin CS following taste-drug pairings because they are anticipating the rewarding rather than the aversive properties of the drug. Oddly, however, while all other drugs of abuse tested suppress intake of a gustatory CS, the highly reinforcing drug, heroin, is reportedly ineffective. The present study reexamined this issue in both water-deprived and water-replete rats using procedures that sustain both morphine- and cocaine-induced suppression of CS intake. The results showed that heroin greatly reduced CS intake following saccharin-heroin pairings and that this effect was less variable when assessed in water-replete subjects. When taken with other reports, these data suggest that rats suppress intake of a saccharin CS in anticipation of the availability of all drugs of abuse tested.

Human taste contrast and self-reported measures of anxiety.

Successive negative taste contrast in humans was demonstrated with a common taste stimulus, i.e., cherry-flavored Kool-Aid. A total of 31 male and female college-aged participants rated a 7% sucrose solution which was cherry-flavored as less sweet when it was preceded by a 28% rather than a 7% sucrose solution which was cherry-flavored. Because drugs such as the benzodiazepines affect taste contrast in rats and act as anxiolytics in humans, the present experiment also examined whether several self-reported measures of anxiety were related to taste contrast in humans. Neither scores on Taylor's Manifest Anxiety Survey nor those on the State-Trait Anxiety Inventory were related to "sweetness" ratings or contrast effects.