Does nicotine alter what is learned about non-drug incentives?

Nicotine is one of the most addictive drugs known to man, yet it has limited reinforcing effects in humans and non-human animals when it is not self-administered in tobacco products. One hypothesis for these paradoxical effects of nicotine is that the effects of the drug in the brain alter acquisition of incentive learning. The hypothesis for this study is that nicotine will increase the value of cues paired with a reward. To test this hypothesis, 26 Sprague Dawley Male rats were randomly assigned to one of three groups Pre-NIC (the critical experimental group), Post-NIC and SAL. Each group received a subcutaneous injection 15 min prior to testing and another injection 1-3 h after testing. For the Pre-NIC group, nicotine (0.4 mg/kg base) was injected 15 min before test sessions; placebo was administered after testing. For the Post-NIC group the order of injections was reversed, and this manipulation controls for total exposure to nicotine. The SAL groups received placebo injections before and after testing. Rats were shaped to respond for 10% sucrose for pressing an illuminated nose-key (Experiment 1) or 0.2% saccharin for pressing a lever (Experiment 2). Responding in the Pre-NIC group was higher than all other groups in Experiment 2 (saccharin reward); however, responding in the three groups was similar in Experiment 1 (sucrose reward). This paradigm highlights how nicotine can increase motivation for rewards, but that the facility of operant behaviors and caloric value of the reward may mask this effect.