Suppressive and enhancing effects of nicotine on food-seeking behavior

Abstract

The present study examined how systemic low doses of nicotine affect the microstructure of reinforced food-seeking behavior in rats. Rats were first given an acute saline or nicotine treatment (0.1-0.6mg/kg, with an inter-injection interval of at least 48h), and then a chronic saline or nicotine treatment (0.3mg/kg/day for 10 consecutive days). Immediately after each injection, rats were required to press a lever five times to obtain food that was available at unpredictable times (on average every 80s) with constant probability. Acute nicotine dose-dependently suppressed behavior prior to the delivery of the first reinforcer, but enhanced food-reinforced behavior afterwards. These effects were primarily observed in the time it took rats to initiate food-seeking behavior. Enhancing effects were also observed in the microstructure of food-seeking behavior, with lower nicotine doses (0.1-0.3mg/kg) increasing the rate at which response bouts were initiated, and higher doses (0.3-0.6mg/kg) increasing within-bout response rates. A pre-feeding control suggests that changes in appetite alone cannot explain these effects. Over the course of chronic nicotine exposure, tolerance developed to the suppressive, but not to the enhancing effects of nicotine on food-seeking behavior. These results suggest that (a) lower doses of nicotine enhance the reward value of food and/or food-associated stimuli, (b) higher doses of nicotine enhance motoric activity, and (c) ostensive sensitization effects of nicotine on behavior partially reflect a tolerance to its transient suppressive motoric effects.

Development of a novel rodent rapid serial visual presentation task reveals dissociable effects of stimulant versus nonstimulant treatments on attentional processes

“…However, it is unclear as to how much nonattentional effects (response latencies) contribute to improvements in accuracy in this task. We also found an increase in collection latency at the highest dose, which may reflect effects on the motivation for reward and food-rewarded behaviors (Romero et al, 2018 ). This is difficult to compare to some key studies (Mirza & Stolerman, 1998 ; Stolerman et al, 2000 ) because of a lack of reporting on this parameter.…”

Development of a novel rodent rapid serial visual presentation task reveals dissociable effects of stimulant vs non-stimulant treatments on attention

“…However, it is unclear as to how much non-attentional effects (response latencies) contribute to improvements in accuracy in this task. We also found an increase in collection latency at the highest dose which may reflect effects on the motivation for reward and food-rewarded behaviors [55]. This is difficult to compare to some key studies [31,54] due to a lack of reporting on this parameter.…”

Microstructural meal pattern analysis reveals a paradoxical acute increase in food intake after nicotine despite its long-term anorexigenic effects

“…These results are particularly striking considering that a similar microstructural analysis conducted by Cooper and van der Hoek of feeding behavior after administration of cocaine, another psychostimulant and anorectic substance, was associated with a complete suppression of feeding, with the duration of suppression proportional to the dose (Cooper & van der Hoek 1993 ). Additionally, a recent study by Romero et al employed microstructural analysis techniques to analyze the reinforcer-enhancing effects of nicotine on food-seeking behavior (Romero et al 2018 ). They found that lower doses of nicotine administered via injection increased the rate of food-seeking bouts.…”

“…For example, microstructural meal pattern analysis shows that the acute administration of cocaine, a potent anorectic drug, decreases food intake in rats (Cooper & van der Hoek 1993 ). To date, only one study by Romero et al has used microstructural analysis to analyze components of feeding behavior in relation to nicotine intake; their study focused on the reinforcing effects on nicotine on food-seeking behavior (Romero et al 2018 ). However, there are currently no studies comparing the effects of nicotine on acute vs. long-term feeding behavior.…”