Food Reinforcement Research Articles

Formation of Different Strategies of Competitive Foraging Behavior in Rats.

We studied competitive interactions of rats during instrumental foraging behavior. Two groups of animals were revealed: rats with predominance of operant actions for getting food reinforcements (donors) and kleptoparasites that more often get food after instrumental acts of the partners. Intergroup differences began to appear and increased from 3-4 paired experiments. It was revealed that at the individual stage of learning the instrumental skill, donor rats were faster in learning and showed high foraging activity with shorter latency in comparison with kleptoparasites, which were initially slower and performed a large number of inter-signal actions in the form of unconditioned peeking into the feeder.

Sustainability of food systems and reinforcement of the science-policy interface: Re-focusing on priorities

Sustainability of food systems and reinforcement of the science-policy interface: Re-focusing on priorities

Reinforcing value of food, enriched home environment, and changes in percent overweight in children.

The decision to eat is often a choice made in the context of food and non-food alternatives. However, no research, to the authors' knowledge, has assessed the combination of the motivation to eat, as indexed by the relative reinforcing value of food (RRVFOOD ), and the enriched home environment, i.e., access to activities that can serve as alternatives to eating on weight gain. This study used a cross-sectional design to study how RRVFOOD and the enriched home environment predict percent overweight change over 2 years in 291children aged6to9yearsandof varying socioeconomic status. Results showed that RRVFOOD and access to food were positively associated with baseline percent overweight, and anenriched home environment was negatively related to baseline percent overweight. RRVFOOD and anenriched home environment interacted to predict change in percent overweight. Children with a high relative RRVFOOD and a relatively non-enriched environment showed the greatest relative weight gain. These results suggest that providing an enriched home environment may reduce the effects of food reinforcement and being motivated to eat on weight gain in childhood, and this represents a novel approach to intervention that can be usedto strengthen current behavioral approaches to prevent obesity in children.

Exploring the Social Reinforcing Value of Brushing in Equine-Assisted Services: A Comparative Study with Food Reinforcement

Abstract Brushing is one of the most common human-horse interactions in Equine-Assisted Services (EAS). Previous research has shown both positive and negative effects of brushing on horses’ behavior and physiological states. One of the primary reasons horses are included in services such as mental and behavioral healthcare is to provide human clients with positive relational experiences; however, more empirical research is needed to determine if horses also receive socially derived benefits from their interactions with human clients. Therefore, we set out to determine whether brushing can function as a social reinforcer for horses utilized in EAS in comparison to food reinforcement. Six EAS horses from a university-based Premier Accredited Professional Association of Therapeutic Horsemanship, International center in the Southwestern Region of the United States participated in a single-subject reversal ABCABC design experiment, in which stimuli (A: Brushing, B: Food, and C: Control [Extinction]) were provided contingent on an arbitrary behavior (nose touch to the experimenter’s closed fist). All horses exhibited maximal or near-maximal responding in the food condition, but low responding in the brushing and control conditions. Data indicated that brushing was not an effective reinforcer for horses compared to food, and this could suggest brushing is a low-value reinforcer. Alternatively, it is possible to access to food at relatively short intervals in time during the experiment may have impacted the reinforcing value of brushing. Human-animal interaction proponents are increasingly calling attention to the need to ensure that equine-inclusive healthcare services address horse welfare, including the promotion of positive welfare experiences. Results from this study support the need for more research on identifying optimal interactions that can promote mutual benefits to both humans and horses participating in EAS.

The conjunction fallacy in rats

Humans and other animals are capable of reasoning. However, there are overwhelming examples of errors or anomalies in reasoning. In two experiments, we studied if rats, like humans, estimate the conjunction of two events as more likely than each event independently, a phenomenon that has been called conjunction fallacy. In both experiments, rats learned through food reinforcement to press a lever under some cue conditions but not others. Sound B was rewarded whereas Sound A was not. However, when B was presented with the visual cue Y was not rewarded, whereas AX was rewarded (i.e., A-, AX+, B+, BY-). Both visual cues were presented in the same bulb. After training, rats received test sessions in which A and B were presented with the bulb explicitly off or occluded by a metal piece. Thus, on the occluded condition, it was ambiguous whether the trials were of the elements alone (A or B) or of the compounds (AX or BY). Rats responded on the occluded condition as if the compound cues were most likely present. The second experiment investigated if this error in probability estimation in Experiment 1, could be due to a conjunction fallacy, and if this could be attenuated by increasing the ratio of element/compound trials from the original 50-50 to 70-30 and 90-10. Only the 90-10 condition (where 90% of the training trials were of just A or just B) did not show a conjunction fallacy, though it emerged in all groups with additional training. These findings open new avenues for exploring the mechanisms behind the conjunction fallacy effect.

Topographical aspects of brief-stimulus presentations: A re-examination of the problem of conditioned reinforcement

Three pigeons were exposed to second-order schedules in which responding under a fixed-interval (FI) component schedule was reinforced according to a variable-interval (VI) schedule of food reinforcement. Completion of each component resulted in either (1) brief presentation of a stimulus present during reinforcement (paired brief stimulus), (2) brief presentation of a stimulus not present during reinforcement (nonpaired brief stimulus), or (3) no stimulus presentation (tandem schedule). Under the two nonpaired brief stimulus conditions, either a change in keylight color or onset of houselight illumination was used as the brief stimulus. Similar patterns of keypecking occurred under tandem and nonpaired keylight brief-stimulus presentations, whereas nonpaired houselight brief-stimulus presentations generated positively accelerated within-component keypeck patterning for two pigeons. When the same keylight brief stimulus was paired with food, positively accelerated patterns of keypecking were obtained for all pigeons. Differences in the effects of nonpaired brief-stimulus presentations on second-order schedule performance suggest that component schedule patterning under nonpaired brief-stimulus procedures is a function of the particular type of stimulus used (i.e., houselight versus keylight). These results suggest that (1) brief houselight illumination may function as a sensory reinforcer, and (2) a briefly presented food-paired stimulus can function as an effective conditioned reinforcer.

The antidepressant agomelatine attenuates morphine-induced reinstatement but not self-administration or precipitated withdrawal

BackgroundExogenous melatonin appears to have anti-addictive properties and was recently shown to improve mental health and metabolic measures in patients receiving chronic opioid maintenance therapy. Agomelatine is a marketed antidepressant which acts as a melatonin agonist. We evaluated its effects using a rat model of morphine-reinforced behavior. MethodsAfter pretreatment with noncontingent morphine, male Wistar rats were trained to self-administer intravenous morphine (1.0 mg/kg-injection) under a progressive-ratio schedule. Rats were pretreated with vehicle or agomelatine during extinction, reinstatement, and reacquisition of morphine-reinforced behavior. ResultsDaily treatment with 10 mg/kg-day of agomelatine decreased the number of ratios completed and prolonged latency during morphine-induced reinstatement. There were no significant effects on cue-induced reinstatement, morphine self-administration, or naloxone-precipitated withdrawal. Treatment with 32 mg/kg-day of agomelatine caused postural changes. That dose prolonged withdrawal-induced loss of body weight and caused delayed reductions in food reinforcement. SummaryIn addition to postural effects, high-dose agomelatine worsened the course of spontaneous withdrawal and produced nonspecific effects on food-reinforced behavior. When administered at a selective dose, agomelatine did not modify morphine self-administration or precipitated withdrawal, but decreased morphine-induced reinstatement. Our findings show potential detrimental effects of high-dose agomelatine, with reductions in opioid-seeking behavior after a lower, more selective dose.

Choice between food and cocaine reinforcers under fixed and variable schedules in female and male rhesus monkeys.

Illicit drugs like cocaine may be uncertain in terms of the time and effort required to obtain them. Behavior maintained by variable schedules resembles excessive drug-taking compared with fixed schedules. However, no prior research has examined fixed versus variable schedules in drug versus nondrug choice. The present study evaluated cocaine versus food choice under fixed- (FR) and variable-ratio (VR) schedules. The simpler food versus food and cocaine versus cocaine arrangements also were included. Adult female (n = 6) and male (n = 7) rhesus monkeys chose between cocaine (0.01-0.18 mg/kg/injection) and food (4 pellets/delivery), food and food (4 pellets/delivery), or cocaine and cocaine (0.018-0.03 mg/kg/injection) under FR and VR 100 and 200 schedules. In cocaine versus food choice, cocaine's potency to maintain choice was greatest when available under a VR 100 or 200 schedule and food under an FR schedule and was lowest when cocaine was available under an FR 200 schedule and food was available under a VR 200 schedule. In food versus food choice, males chose food associated with a VR schedule more than food associated with an FR schedule. In cocaine versus cocaine choice, females and males chose cocaine associated with a VR schedule more than cocaine associated with an FR schedule, particularly under VR 200. These findings suggest that uncertainty in terms of time and effort required to obtain cocaine, or perhaps the occasional low-cost access that results from VR schedules, results in greater allocation of behavior toward drug reinforcers at the expense of more certain, nondrug alternatives. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Efectos de variar el nivel de privación de comida sobre el valor reforzante del agua en el beber inducido por el programa

Scheduled-induced drinking (SID) occurs when food-deprived rats are exposed to intermittent schedules of food reinforcement. In recent years, SID has been considered as operant behavior reinforced directly by water and it has been suggested that food deprivation may function as a motivating operation that increases the reinforcing value of water. The purpose of the study was to determine the effects of varying food-deprivation levels on water reinforcing efficacy during SID sessions. In successive phases, three rats were maintained at their free-feeding weights, or were food deprived at 90 or 80% of their free-feeding weights. Rats were exposed to SID sessions in which food was delivered according to a tandem fixed- time 176- s, differential-reinforcement-of-other-behavior 4-s. Lever presses were reinforced with water according to a progressive-ratio 5 schedule. In general, response rates for water and break points increased with increases in food-deprivation level. The results complement earlier findings showing that SID is operant behavior reinforced directly by water.

Reducing relative food reinforcement of infants using a music enrichment program: a randomized, controlled trial

Food reinforcement or one's motivation to eat may be established early in life; it might not be the food reinforcement per se that drives weight gain, but rather the imbalance between food and nonfood reinforcement. We implemented a 2-y randomized, controlled trial to assess the effects of a music enrichment program (music, n=45) compared with an active play date control (control, n=45) in 9- to 15-mo-old healthy infants who were strongly motivated to eat. The 12-mo intensive intervention phase included 4 semesters of Music Together® or a play date program (Winter, Spring, Summer, and Fall), comprised of once per week group meetings, followed by a 12-mo maintenance phase with monthly meetings. Parents were encouraged to listen to the Music Together® program CD or play with the play date group's toy with their infants at home, respectively. We performed a modified intention-to-treat analysis using all randomly assigned, non-excluded subjects for the outcome measures [relative reinforcing value of food (RRVfood), food reinforcement, music reinforcement, and weight-for-length z-score (WLZ)]. There were significant differential group changes across time for RRVfood (group × month; P=0.016; Cohen's f2=0.034). The music group had significantly greater RRVfood decreases than the control group from baseline to the end of the intensive intervention phase (music change = -0.211; control change = -0.015; P=0.002; Cohen's D=0.379). However, these differences were not maintained during months 12-24 (music change = -0.187; control change = -0.143; P=0.448; D=0.087). We observed an overall moderation effect by sex for food reinforcement and WLZ. Boys in the music group had a significant attenuation in food reinforcement and WLZ compared with boys in the control group. This study extends our knowledge in infant eating behavior by providing insight into the role of nonfood alternatives in altering one's motivation to eat. There may be sex differences in altering one's motivation to eat.This trial was registered at clinicaltrials.gov as NCT02936284.

A new paradigm for investigating the etiology of obesity in early childhood: Exposure to added sugars and hyper-palatable foods in infancy and dysregulation of food reinforcement processes.

A new paradigm for investigating the etiology of obesity in early childhood: Exposure to added sugars and hyper-palatable foods in infancy and dysregulation of food reinforcement processes.

Chronic restraint stress impairs voluntary wheel running but has no effect on food-motivated behavior in mice

Chronic restraint stress is known to cause significant alterations of mitochondrial biology. However, its effects on effort-based behavior and the sensitivity of these effects to treatments that restore mitochondrial function have not been assessed. Based on the hypothesis that the behavioral consequences of this stressor should be more severe for an energy demanding activity than for an energy procuring activity, we compared the effects of chronic restraint stress on the performance of male mice trained to use a running wheel or to nose poke for a food reward in an operant conditioning cage. In accordance with our hypothesis, we observed that exposure of mice to 2-hour daily restraint sessions for 14 to 16 days during the light phase of the cycle reliably decreased voluntary wheel running but had no effect on working for food in a fixed ratio 10 schedule of food reinforcement or in a progressive ratio schedule of food reinforcement. This dissociation between the two types of behavioral activities could reflect an adaptive response to the constraint imposed by chronic restraint stress on mitochondria function and its negative consequences on energy metabolism. To determine whether it is the case, we administered mesenchymal stem cells intranasally to chronically restrained mice to repair the putative mitochondrial dysfunction induced by chronic restraint stress. This intervention had no effect on wheel running deficits. Assessment of mitochondrial gene expression in the brain of mice submitted to chronic restraint stress revealed an increase in the expression of genes involved in mitochondrial biology that showed habituation with repetition of daily sessions of restraint stress. These original findings can be interpreted to indicate that chronic restraint stress induces behavioral and mitochondrial adjustments that contribute to metabolic adaptation to this stressor and maintain metabolic flexibility.

Cognitive tests in zebrafish (<i>Danio rerio</i>): T- and Y-mazes

T- and Y-shaped mazes are traditionally used to assess spatial learning and memory of zebrafish. In the installation of the T-shaped maze, the fish are taught to swim into the desired sleeve and not swim into the wrong one using both positive (for example, food reinforcement) and negative (for example, electric current) stimuli to form more persistent reflexes. The Y-shaped maze is based on the principle of spontaneous choice. Spontaneous choice behavior describes the tendency of animals to change their direction of rotation in a series of successive turns. Each choice statistically depends on the previous one, which indicates its mnestic origin. Unlike other types of memory tasks, testing in the Y-shaped maze does not require prior training or reinforcement (as in the T-shaped maze). Both aquatic mazes are becoming useful tools for assessing zebrafish cognitive phenotypes.

Effects of the cannabinoid CB1-receptor neutral antagonist AM4113 and antagonist/inverse agonist rimonabant on fentanyl discrimination in male rats

Evidence suggests the existence of a functional interaction between endogenous cannabinoid (CB) and opioid systems. Thus, targeting CB1 receptors might be a viable approach to develop new medications for opioid use disorders (OUD). The present studies were undertaken to evaluate the effects of the neutral CB1 antagonist AM4113 and the CB1 antagonist/inverse agonist rimonabant in male rats trained to discriminate 0.032 mg/kg fentanyl from saline under a 10-response fixed-ratio (FR-10) schedule of food reinforcement. Results show that the µ-opioid agonists (fentanyl, oxycodone, and morphine) substituted fully and dose-dependently for fentanyl, whereas pretreatment with the µ-opioid antagonist naltrexone antagonized fentanyl's discriminative-stimulus effects. In interaction studies, AM4113 (0.32 or 1.0 mg/kg) was more effective in blocking fentanyl discrimination at 10-fold lower doses that did not modify rates of food-maintained responding, whereas rimonabant (1.0–10 mg/kg) produced some attenuation of fentanyl's discriminative-stimulus effects at the highest dose tested which also significantly decreased response rates. These results extend our recent work showing that AM4113 can effectively block the behavioral effects of heroin without producing rimonabant-like adverse effects. Taken together, these data suggests that CB1 neutral antagonists effectively block the behavioral effects of structurally distinct morphinan (heroin) and phenylpiperidine-based (fentanyl) opioids and may provide a novel therapeutic option for the treatment of OUD.

Nondrug reinforcers contingent on alternative behavior or abstinence increase resistance to extinction and reinstatement of ethanol-maintained behavior.

The effects of delivering nondrug alternative reinforcement on resistance to extinction and reinstatement of rats' ethanol-maintained lever pressing were evaluated in two experiments. In both, rats self-administered ethanol by lever pressing in a two-component multiple schedule during baseline. In the Rich component, alternative food reinforcement was made available for performing an alternative response (Experiment 1) or according to a differential-reinforcement-of-other-behavior schedule for lever pressing (Experiment 2). In the Lean component, only ethanol was available. Moreover, the frequency of alternative reinforcement was manipulated across conditions in Experiment 1. Following baseline, lever pressing was extinguished in both components by suspending ethanol reinforcement, and alternative food reinforcers were discontinued. Finally, to test for reinstatement, ethanol reinforcers were delivered independently of lever pressing in both components. In both experiments, proportion-of-baseline response rates were higher during extinction and reinstatement testing in the Rich component than in the Lean component (although differentiation was not observed at the lowest frequency of alternative reinforcement in Experiment 1). Thus, alternative nondrug reinforcers increased resistance to extinction and reinstatement of rats' ethanol-maintained lever pressing, even when those reinforcers were delivered contingently on an alternative response or on abstinence from lever pressing.

Effects of a cue associated with cocaine or food reinforcers on extinction and postextinction return of behavior.

Studies of instrumental responding often include the delivery of a cue that is coincident with the delivery of the reinforcer. One purpose of this is for the cue to be removed during extinction and then presented later to assess whether responding returns (cue-induced reinstatement). In two experiments, we examined the effects of having a cue associated with reinforcement present or absent during extinction. In Experiment 1, the cue was associated with fixed ratio responding for intravenous cocaine or food pellets in one context (Context A), followed by extinction in another context (Context B), where responding produced the cue in one group but did not produce the cue in the other group. Afterward, contextual renewal was assessed with and without the cue in Context A. During extinction, a cue previously associated with cocaine reinforcement caused an increase in responding initially (an extinction burst) and throughout 16 2-hr extinction sessions, as well as weakened contextual renewal when animals were tested with the cue in Context A. In contrast, there were few detectable effects of the cue on extinction and contextual renewal when food pellets were the reinforcer. In Experiment 2, effects of a cue during extinction of progressive ratio responding were revealed with food pellets when animals showed weakened responding on the initial trials of postextinction reacquisition sessions. These experiments demonstrate that the presence of a cue associated with reinforcement during extinction may prolong responding in the short term while creating a more persistent form of extinction that resists relapse. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Influences of indication response requirement and target prevalence on dogs’ performance in a scent-detection task

Scent-detection dogs assist humans with many socially significant tasks and hold promise for assisting with many others. However, the methods used to train scent-detection dogs and the conditions under which they work are highly variable, and the influences of many relevant factors on scent-detection performance are poorly understood. Using an automated scent-detection apparatus that allowed the dogs to work independently from a handler, we evaluated the influence of two factors on scent-detection performance with amyl acetate as the target. In the first experiment in this study, we examined the influence of the indication response requirement on the performance of five dogs trained to perform a scent-detection task. The indication response consisted of the dogs breaking an infrared beam in a port through which they accessed samples. The response requirement was manipulated by adjusting the duration of the beam break that was required to activate food reinforcement if the target was present. As the indication response requirement increased, dogs’ ability to detect the target remained unchanged, as indicated by stable log d measures across durations (p = .09), but their response bias, represented by log B, shifted from a tendency to indicate that targets were present to a tendency to indicate that targets were absent (p < 0.001). In the second experiment, we examined the influence of target prevalence, or the proportion of samples that are target samples, on four dogs’ scent-detection performance. As target prevalence decreased, the dogs’ ability to detect the target remained unchanged (p = 0.13), but their response bias shifted from a tendency to indicate that the targets were present to a tendency to indicate that targets were absent (p < 0.001). This finding aligns with the “low-prevalence effect,” which is commonly observed in human signal detection research. The findings from both experiments have important theoretical and practical implications. For example, by adjusting response effort, we can alter dogs’ response bias toward or away from indicating the presence of targets and, by having a clear understanding of the influence of target prevalence on bias, we can make informed decisions about the need to artificially increase target prevalence when dogs are searching for rare targets.

Assessing the performance of brushtail possums (Trichosurus vulpecula) on the Mechner counting procedure.

This study assessed brushtail possums' performance on the Mechner counting procedure. Six brushtail possums were required to produce different Fixed-Ratio (FR) response targets by lever pressing. Their responses provided access to food reinforcement delivered either upon completing the target FR response requirement on a single lever or, in different conditions, on completing the target FR before producing an additional response on a second lever. The mean number of responses on the first lever before switching to the second lever typically occurred just above the target FR response requirement (FR: 4, 8, 16, 32 and 64). The variability in the number of switches between the levers around the target FR decreased from the first 10days to the last 10days, indicating an improvement in counting accuracy over sessions. The time to switch between the first and second lever was consistently variable across response requirements suggesting that it is unlikely the possums were using time to predict when to switch levers. This research further supports the use of the Mechner procedure as a method for measuring counting ability in animals and confirms the possibility of numerical competence in a marsupial species.

Chemokine Receptor Antagonism Decreases Drug Choice and Modifies Opioid Analgesia in Rats

Substance use disorders (SUDs) and overdose deaths have reached unprecedented levels despite considerable efforts to develop pharmacotherapies for their treatment and prevention. Chemoattractant cytokines (‘chemokines’) are immune system messengers that can alter the therapeutic and abuse‐related effects of opioids and stimulants. Therefore, the aims of this study were to evaluate the effectiveness of Maraviroc, a CCR5 antagonist, and AMD3100, a CXCR4 antagonist, to alter 1) the self‐administration of fentanyl, an opioid, and cocaine, a stimulant, using a food versus drug choice procedure and 2) the analgesic effects of fentanyl in a radiant heat assay. Adult male Sprague Dawley rats were trained to respond under a fixed ratio (FR) 5 on one lever to receive an infusion of fentanyl (n=8), and on an alternate lever to receive food (grain‐based pellet). The choice procedure consisted of 5 sequential 20‐min components, each separated by a 2‐min intercomponent interval. Food was available across all five components, with increasing unit doses of fentanyl (0.00032‐0.01 mg/kg/infusion) available during components 2‐5; no drug was available during component 1. Once responding stabilized, rats underwent a series of drug pretreatment tests, including: naloxone (1, 3.2 mg/kg; IP), haloperidol (0.01‐0.1 mg/kg; IP), Maraviroc (1‐17.8 mg/kg; IP), and AMD3100 (1‐17.8 mg/kg; IP). A separate cohort of 8 adult male Sprague Dawley rats was used to evaluate the effects of Maraviroc (10 mg/kg; IP), and AMD3100 (10 mg/kg; IP), on paw withdrawal latencies in a thermal nociception procedure following cumulative doses of fentanyl (0.01‐0.1 mg/kg; IP). In rats responding for food or fentanyl, naloxone reduced fentanyl choice while increasing choice of food, whereas haloperidol had little effect on the choice for fentanyl, but decreased responding on both levers at large doses. Maraviroc and AMD3100 had similar effects all rats tested, effectively reallocating behavior away from the drug and towards the food reinforcer. At the largest dose tested, Maraviroc (17.8 mg/kg; IP) disrupted behavior in the early portions of the session, suggestive of a sedative effect in some animals. Maraviroc and AMD3100 did not significantly modify the analgesic effects of fentanyl during tests of thermal nociception. These data suggest that antagonism of CXCR4 and CCR5 may be of use in the ongoing effort to develop medications for the treatment of SUDs.

Effects of Cannabinoid Agonists and Antagonists in Rats Discriminating Fentanyl

Extensive evidence suggests the existence of a functional interaction between endogenous cannabinoids and opioid systems. Targeting cannabinoid CB1 receptors might be a promising approach for developing new medications for opioid addiction. The present studies were undertaken to evaluate the effects of CB1 agonists and antagonists in rats (n=8) trained to discriminate, i.p., injections of 0.032 mg/kg fentanyl from saline on a 10‐response fixed‐ratio (FR‐10) schedule of food reinforcement. Results show that the µ‐opioid agonists (fentanyl, morphine, and oxycodone) substituted fully for fentanyl, whereas the muscarinic antagonist atropine did not substitute for fentanyl. The CB1 agonists Δ9‐THC, AM2201, and AM8936 all partially substituted for fentanyl’s discriminative‐stimulus effects suggesting some overlap in the discriminative‐stimulus effects of cannabinoid agonists and fentanyl. Pretreatment studies with a µ‐opioid receptor antagonist show that naltrexone antagonized fentanyl’s effects. Interestingly, pretreatment studies with CB1 antagonists show that rimonabant (inverse agonist) produced some attenuation of fentanyl’s discriminative‐stimulus effects at doses that significantly decreased response rates, whereas the neutral CB1 antagonist AM4113 blocked fentanyl discrimination at doses that did not modify rates of responding. Our findings are consistent with our recent work showing that AM4113 attenuates heroin self‐administration in rats, without producing depressive‐like effects. Collectively, these data suggests that CB1 neutral antagonists that block CB1 receptors with rimonabant‐like potency, devoid of unwanted side‐effects, may be therapeutically advantageous for countering the abuse‐related behavioral effects of opioids.