Nicotine enhances the expression of a conditioned place preference in adult male rats

As the number of cigarette-related deaths has risen over the years, researchers have tried to study and understand cigarettes, their components, and why they are so addictive despite widespread knowledge of their potentially fatal health consequences. Research in recent decades has unveiled that the strength of cigarette addiction could be due in part to the primary reinforcing effects of nicotine. Although these findings may give researchers and medical professionals some answers about this addiction, it does not provide the whole picture. Research conducted more recently has shown that the reinforcement-enhancing effect, a property of nicotine that increases an organism’s behavior in response to an environmental stimulus, could also play a large role in tobacco addiction. Though many studies have observed this phenomenon in an operant paradigm, the effect has yet to be observed using a different model. The present study hypothesized that this effect could be produced using a conditioned place preference (CPP) paradigm. Animals were conditioned to prefer one of two chambers using either a sucrose or cocaine reward. The day after a post-conditioning preference test, the effect of a one-time, acute injection of nicotine on these expressed CPPs was then observed. Results showed a significant effect of nicotine on the expression of both sucrose and cocaine CPPs with animals spending more time in the reward-associated chamber relative to the first post-conditioning preference test and a third preference test preceded by a saline injection. Furthermore, there was no significant difference between the results of the saline and injection-free post-conditioning preference tests. These results show that the reinforcement-enhancing effect can be observed in a classical conditioning paradigm. They also show that in this non-operant paradigm, the reinforcement-enhancing effect can be produced by one acute injection of nicotine in animals with no previous exposure to the drug. These findings can provide more insight into the reinforcing effects caused by a first experience with nicotine