Association for Behavior Analysis International

Previous research has suggested that ethanol consumption may be divisible into bouts of drinking separated by between-bout intervals where no drinking occurs. Relatively few attempts have been made to precisely quantify drinking within this framework. Thus, the goal of the present project was to formalize the study of ethanol consumption in rodents. Six, Long Evans rats were trained to drink an 8% (w/v) ethanol solution. After 4 weeks, all rats were drinking pharmacologically relevant doses of ethanol (approximately 0.5 g/kg per 30 min session). Inter-response time measures obtained from each lick were analyzed with respect to several different approaches. Two approaches in particular, the log-survivor approach (e.g., Shull et al., 2002) and the log-normal approach (e.g., Tolkamp et al., 1998) suggested that the population of response times were segregated into bout and between-bout intervals. The data also suggested that the pauses in licking beyond just a few seconds would easily characterize the end of a bout; this is much shorter than durations used in prior research (e.g., 5 minutes) and suggest previous work has substantially overestimated the durations of ethanol-drinking bouts. Overall, the data show the feasibility of the response-bout approach for characterizing ethanol drinking in laboratory animals.

The cue-induced procedure is an animal model of drug relapse widely used to study drug-seeking behavior. The most used training procedure is briefly described as follow: on Training phase lever press responses in the presence of an odor (SD1) are followed by a stimulus (Sr1) and some drug (SR1), while responses in the presence of another odor (SD2) are followed by another stimulus (Sr2) and water release (SR2). Next, lever press is extinct in the absence of discriminative stimuli and conditioned reinforcers (Extinction phase). Therefore, Sd1 and Sr1 or Sd2 and Sr2 are reintroduced in separte sessions, but lever press responses are not followed by drug or water (Reinstatement phase). Generally, animals are not water of food deprived. Several studies using this procedure have shown that bar-pressed is controlled by SD1 and Sr1 presentation, but not by SD2 and Sr2. Those results are often interpreted as the control acquire by the SD1 over the drug-seeking behavior. This paper presents and discuss results from experiments conducted in our laboratory that consistently showed that the responses observe in the Reinstatement phase of the "cue-induced" procedure are function of the conditioned reinforcer SR1, but not of the discriminative stimulus SD1, regardless of the primary reinforcer (ethanol or sucrose) and schedule of reinforcement (CRF or VR5) used. Considering the experiments from other laboratories that show that SD1 acquire control over behavior when SR1 are not presented in the training phase, we discuss the critical variables that could explain why in the cue-induced procedure the SD1 dont acquire discriminative control over the response and propose specific experiments to analyze SD1 and SR1 interactions.

Rimonabant, a cannabinoid antagonist, has been shown to reduce free-food intake as well as food intake in paradigms in which a single lever or reinforcer is available, but its effects in a choice situation have not yet been examined. The present study examined the effects of rimonabant on genetically obese and lean Zucker rats' responding for food under concurrent schedules of reinforcement, which more ecologically models food selection. Lever-pressing of 10 lean and 10 obese Zucker rats was placed under 3 concurrent variable-interval variable-interval (conc VI VI) schedules of food reinforcement, in which the reinforcer ratios for 45-mg food pellets were 5:1, 1:1, and 1:5. After behavior stabilized under each concurrent schedule, acute doses of rimonabant (0-10 mg/kg) were administered before an experimental session. Allocation of responses was characterized using the generalized matching equation, which allows sensitivity to reinforcer rates (a) to be quantified. Overall, obese Zucker rats exhibited higher sensitivity to reinforcement rates than lean rats, which may indicate a behavioral mechanism that could contribute to obesity. Rimonabant decreased the total number of responses and reinforcers for all rats, but also increased sensitivity, which resulted in an increased efficiency of responding (i.e., fewer responses were required per reinforcer earned).