Abstract
RationaleNicotine promotes alcohol intake through pharmacological and behavioral interactions. As an example of the latter, nicotine can facilitate approach toward food- and alcohol-associated stimuli (“sign-tracking”) in lever-Pavlovian conditioned approach (PavCA) paradigms. However, we recently reported that nicotine can also enhance approach toward locations of reward delivery (“goal-tracking”) triggered by ethanol-predictive stimuli when the location of ethanol delivery is non-static (i.e., a retractable sipper bottle).ObjectiveTo determine whether the non-static nature of the reward location could have biased the development of goal-tracking in our previous study (Loney et al., 2019); we assessed the effect of nicotine in a lever-PavCA paradigm wherein the location of ethanol delivery was static (i.e., a stationary liquid receptacle). Then, to determine whether nicotine’s enhancement of goal-tracking is unique to ethanol-predictive stimuli, we assessed the effect of systemic nicotine on approach triggered by food-predictive stimuli in a lever-PavCA paradigm.MethodsLong–Evans rats were used in two PavCA experiments wherein a lever predicted the receipt of ethanol (15% vol/vol; experiment 1) or food (experiment 2) into a stationary receptacle. Prior to testing, rats were administered nicotine (0.4 mg/kg subcutaneously) or saline systemically.ResultsIn both experiments, nicotine increased measures of goal-tracking, but not sign-tracking.ConclusionNicotine can facilitate approach to reward locations without facilitating approach to reward-predictive stimuli. As such, conceptualization of the mechanisms by which nicotine affects behavior must be expanded to explain an enhancement of goal-tracking by nicotine.
Highlights
While there is limited evidence that the primary reinforcing properties of nicotine alone serve to drive drug-taking (Dar and Frenk, 2004; Caggiula et al, 2009), there is substantial evidence that both smoking and smoking concomitant behaviors are principally controlled by nicotine’s interactions with reward-associated stimuli
We have recently shown that nicotine enhances goal-tracking triggered by an ethanol-predictive stimulus (Loney et al, 2019) when the reward delivery location was non-static
We found that nicotine enhances goal-tracking triggered by an ethanol-predictive stimulus in a lever-PavCA paradigm where the reward delivery location was static
Summary
While there is limited evidence that the primary reinforcing properties of nicotine alone serve to drive drug-taking (Dar and Frenk, 2004; Caggiula et al, 2009), there is substantial evidence that both smoking and smoking concomitant behaviors are principally controlled by nicotine’s interactions with reward-associated stimuli (for review see Caggiula et al, 2009). Nicotine’s impact on operant responding is not limited solely to nicotine-associated stimuli, as nicotine produces similar effects on responding in the presence of stimuli that are associated with non-nicotine rewards (Caggiula et al, 2009), including alcohol (Le et al, 2003), which is commonly coabused with nicotine (Falk et al, 2006; Weinberger et al, 2016, 2015) The basis for such interactions between nicotine and rewardassociated stimuli may be due to nicotine’s incentive-amplifying properties that act on reward-associated stimuli (Caggiula et al, 2009; Palmatier et al, 2014). An effect of nicotine must be demonstrated using measures that reflect the incentive value of a stimulus
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