Drugs such as alcohol, amphetamine, cocaine, diazepam, nicotine, methylphenidate and morphine, which tend to be abused by humans often also serve as positive reinforcers in rats. These drug agents, paradoxically produce conditioned taste avoidance (CTA) when paired with a flavored solution. Recent evidence suggests that CTAs based upon such positively reinforcing agents may differ from CTAs based on drugs which are ineffective reinforcers. Based upon results that employ the Taste Reactivity (TR) test, it appears that flavors paired with nonreinforcing drugs become conditionally unpalatable, but flavors paired with reinforcing drugs do not become conditionally unpalatable, even though they are avoided. The experiments proposed in Section I will systematically assess the ability of the TR test to distinguish reinforcing from nonreinforcing drugs. The experiments proposed in Section II of the proposal present a tool for comparing the reinforcing properties of different psychoactive agents within the same animal. By using a 3 - 4 choice place conditioning apparatus, we can determine whether rats prefer a chamber paired with Drug A (i.e., cocaine) to a chamber paired with Drug B (i.e., morphine). To my knowledge, this serves as the first test that directly compares the reinforcing properties of different drugs within the same animal. Finally, the experiments proposed in Section III measure the direct effects of psychoactive agents on palatability. Pretreatment with reinforcing drugs appears to reduce the aversiveness of bitter quinine solution. The experiments proposed in Section III will determine whether this effect is consistent across reinforcing agents.
