Effect of sucrose availability on wheel-running as an operant and as a reinforcing consequence on a multiple schedule: Additive effects of extrinsic and automatic reinforcement

Comparing extinction and contrast effects for operant wheel running and lever pressing on a multiple schedule

Extinction and positive contrast effects were assessed on a multiple schedule with lever pressing as the operant in one component and wheel running as the operant in the other component. FR 15 schedules produced 15% sucrose reinforcement in each component. Contrast for both operants was generated by placing responding in the alternate component on extinction. Results showed that extinction decreased and contrast increased both lever-pressing and wheel-running rates. However, the magnitude of the changes was greater for lever pressing. Extinction increased and contrast decreased postreinforcement pause (PRP) duration for lever pressing, but for wheel running, extinction decreased PRP duration while contrast did not change PRP duration. Finally, outcomes for lever pressing decreased with extinction and increased with contrast, but for wheel running, outcomes did not change with extinction and increased with contrast. These differences in contrast and extinction effects were explained by an automatic reinforcement effect generated by wheel-running, but not lever pressing. These findings provide further support for an automatic reinforcement effect generated by wheel running.

Development and implementation of a Dependable, Simple, and Cost-effective (DSC), open-source running wheel in High Drinking in the Dark and Heterogeneous Stock/Northport mice

Maintaining healthy and consistent levels of physical activity (PA) is a clinically proven and low-cost means of reducing the onset of several chronic diseases and may provide an excellent strategy for managing mental health and related outcomes. Wheel-running (WR) is a well-characterized rodent model of voluntary PA; however, its use in biomedical research is limited by economical and methodical constraints. Here, we showcase the DSC (Dependable, Simple, Cost-effective), open-source running wheel by characterizing 24-h running patterns in two genetically unique mouse lines: inbred High Drinking in the Dark line 1 [iHDID-1; selectively bred to drink alcohol to intoxication (and then inbred to maintain phenotype)] and Heterogeneous Stock/Northport (HS/Npt; the genetically heterogeneous founders of iHDID mice). Running distance (km/day), duration (active minutes/day) and speed (km/hour) at 13-days (acute WR; Experiment 1) and 28-days (chronic WR; Experiment 2) were comparable to other mouse strains, suggesting the DSC-wheel reliably captures murine WR behavior. Analysis of 24-h running distance supports previous findings, wherein iHDID-1 mice tend to run less than HS/Npt mice in the early hours of the dark phase and more than HS/Npt in the late hours of dark phase/early light phase. Moreover, circadian actograms were generated to highlight the broad application of our wheel design across disciplines. Overall, the present findings demonstrate the ability of the DSC-wheel to function as a high-throughput and precise tool to comprehensively measure WR behaviors in mice.

Preference for vigorous exercise versus sedentary sucrose drinking: an animal model of anergia induced by dopamine receptor antagonism

Motivation has activational and directional components. Mesolimbic dopamine is critical for the regulation of behavioral activation and effort-related processes in motivated behaviors. Impairing mesolimbic dopamine function leads to fatigue and anergia, but leaves intact other aspects of reinforce seeking behaviors, such as the consummatory or hedonic component. In male Swiss mice, we characterized the impact of dopamine antagonism on the selection of concurrently presented stimuli that have different vigor requirements. We analyzed running wheel activity versus sucrose solution intake, typically used as a measure of anhedonia. Results are compared with data from nonconcurrent presentation to those stimuli. In the concurrent presentation experiment, control mice preferred to spend time running compared to sucrose intake. Dopamine antagonism shifted relative reinforcer preference, reducing time spent on the running wheel, but actually increasing time-consuming sucrose. Mice increased frequency of bouts for both reinforcers, suggesting that there was fatigue in the running wheel rather than aversion. Moreover, satiation or habituation by preexposing animals to both reinforcers did not shift preferences. In the nonconcurrent experiments, haloperidol reduced running wheel but had no impact on sucrose consumption. Dopamine antagonism did not change preference for sucrose or total volume consumed. Additional correlational analyses indicated that baseline differences in sucrose consumption were independent of baseline running or novelty exploration. Thus, dopamine antagonism seems to have anergic rather than anhedonic effects, and the concurrent presentation in this setting could be useful for assessing preferences based on effort requirements.

Effects of pre-operant running and sucrose concentration on operant wheel running on a fixed interval schedule of reinforcement

Prior research proposed that temporal control over the pattern of operant wheel running on a fixed interval (FI) schedule of sucrose reinforcement is a function of automatic reinforcement generated by wheel running and the experimentally arranged sucrose reinforcement. Two experiments were conducted to assess this prediction. In the first experiment, rats ran for different durations (0, 30, 60, and 180 min) prior to a session of operant wheel running on a FI 120-s schedule. In the second experiment, the concentration of sucrose reinforcement on a FI 180-s schedule was varied across values of 0, 5, 15, and 25%. In Experiment 1, as the duration of pre-operant running increased, the postreinforcement pause before initiation of running lengthened while wheel revolutions in the latter part of the FI interval increased. In Experiment 2, wheel revolutions markedly increased then decreased to a plateau early in the FI interval. Neither manipulation increased temporal control of the pattern of wheel running. Instead, results indicate that operant wheel running is regulated by automatic reinforcement generated by wheel activity and an adjunctive pattern of running induced by the temporal presentation of sucrose. Furthermore, the findings question whether the sucrose contingency regulates wheel running as a reinforcing consequence.

Effect of amphetamine dose on wheel-running functioning as reinforcement or operant behavior on a multiple schedule of reinforcement

Does the effect of amphetamine on behavior (wheel running) differ depending on the functional role (operant, reinforcement) of that behavior? This study addressed this question using a multiple schedule of reinforcement in which wheel running served as reinforcement for lever pressing in one component and as operant behavior for sucrose reinforcement in the other component. Seven female Long-Evans rats were exposed to a multiple schedule in which pressing a lever on a variable ratio 10 schedule produced the opportunity to run for 15 revolutions in one component and running 15 revolutions produced a drop of 15% sucrose solution in the other component. Doses of 0.5, 1.0, and 2.0 mg/kg D-amphetamine were administered by intraperitoneal injection 20 min prior to a session. As amphetamine dose increased, wheel running decreased in both components - showing no evidence that the effect of the drug on wheel running depended on the function of wheel activity. Notably, lever pressing for wheel-running reinforcement also decreased with amphetamine dose. Drug dose increased the initiation of operant lever pressing, but not the initiation of operant wheel running. We propose that amphetamine dose had common effects on wheel running regardless of its function (reinforcement vs. operant) because wheel-running generates automatic reinforcement and the automatic-reinforcement value of wheel activity is modulated by drug dose.