Background
Phosphatidylethanol (PEth) homologs are ethanol metabolites used to identify and monitor alcohol drinking in humans. In this study, we measured levels of the 2 most abundant homologs, PEth ...16:0/18:1 and PEth 16:0/18:2, in whole blood samples from rhesus macaque monkeys that drank ethanol daily ad libitum to assess the relationship between PEth levels and recent ethanol exposure in this animal model.
Methods
Blood samples were obtained from The Monkey Alcohol Tissue Research Resource. The monkeys were first induced to consume 4% (w/v) ethanol in water from a panel attached to their home cage. Then, monkeys were allowed to drink ethanol and water ad libitum 22 h daily for 12 months and the daily amount of ethanol each monkey consumed was measured. Whole, uncoagulated blood was collected from each animal at the end of the entire experimental procedure. PEth 16:0/18:1 and PEth 16:0/18:2 levels were analyzed by HPLC with tandem mass spectrometry, and the ethanol consumed during the preceding 14 days was measured. Combined PEth was the sum of the concentrations of both homologs.
Results
Our results show that (1) PEth accumulates in the blood of rhesus monkeys after ethanol consumption; (2) PEth homolog levels were correlated with the daily average ethanol intake during the 14‐day period immediately preceding blood collection; (3) the application of established human PEth 16:0/18:1 cutoff concentrations indicative of light social or no ethanol consumption (<20 ng/ml), moderate ethanol consumption (≥ 20 and < 200 ng/ml) and heavy ethanol consumption (≥ 200 ng/ml) predicted significantly different ethanol intake in these animals. PEth homologs were not detected in ethanol‐naïve controls.
Conclusions
This study confirms that PEth is a sensitive biomarker for ethanol consumption in rhesus macaque monkeys. This nonhuman primate model may prove useful in evaluating sources of variability previously shown to exist between ethanol consumption and PEth homolog levels among humans.
This novel study shows that PEth, a direct biomarker of ethanol intake, is present in the blood of Rhesus monkeys after consuming ethanol ad libitum; and that the levels of the two most abundant PEth homologs, PEth 16:0/18:1 and PEth 16:0/18:2, are detectable as a function of daily ethanol consumed. This pre‐clinical model provides a greater experimental control over ethanol dosing, which could help understand and interpret variability found in PEth in human blood samples.
Background
Varenicline has been reported to reduce drinking in smokers and to selectively decrease responding for ethanol (EtOH) versus alternatives in preclinical studies. Such selectivity may ...reflect potential therapeutic effects and the involvement of nicotinic receptors in EtOH reinforcement. However, these studies have been conducted with EtOH and an alternative available in isolation or in separate groups, and selectivity can depend on the context in which reinforcement occurs. Whether varenicline selectivity is maintained when EtOH and an alternative are concurrently available has not been reported. To examine the effects of varenicline on EtOH self‐administration when an alternative is concurrently available, male Lewis rats (n = 5) were trained to respond for EtOH and food under a concurrent FR5 FRX schedule where the fixed ratio (FR) for food was adjusted (FR = 25 or 35 for each subject) to provide similar numbers of EtOH and food deliveries during a 30‐minute session.
Methods
Doses of varenicline (0.56 to 5.6 mg/kg, i.p.) or vehicle were administered 30 minutes before sessions. Effects of varenicline on responding across the session and during each tenth of the session were compared to responding following vehicle treatment.
Results
Lower doses (0.56 to 1.0 mg/kg) of varenicline increased responding for EtOH without affecting responding for food. Higher doses disrupted responding for EtOH and food similarly.
Conclusions
Previous reports of varenicline selectivity on EtOH‐maintained responding do not generalize to other experimental conditions such as a concurrent schedule. The increase in responding for EtOH following lower doses might be due to enhanced EtOH reinforcement, decreased food reinforcement, rate dependency, or greater perseverance on the initial, EtOH response.
Background
During recovery from alcoholism, other behavior likely increases. The development of alternative behavior may reduce attention to alcohol‐associated stimuli. This could result in greater ...persistence of the alternative behavior when individuals again encounter alcohol‐associated stimuli that might precipitate relapse. Developing animal models of this process could facilitate a better understanding of the mechanisms involved in relapse and recovery. However, current preclinical models of recovery and relapse rarely measure alternative behavior. Thus, our objective was to establish a procedure in rats in which an increase in alternative behavior (responding for food) reduced responding for ethanol (EtOH). The amount of responding for food and EtOH was then assessed after re‐exposure to the alcohol‐associated stimulus after varying the number of preceding sessions of increased responding for food and reduced responding for EtOH. These results were compared with those from a parallel group responding for saccharin solution instead of EtOH.
Methods
The solution (EtOH or saccharin) was always available following 5 responses. Presentation of flashing stimulus lights indicated food delivery followed 150 responses and resulted in responding predominately for the solution (84 to 86% of total responses). Presentation of solid stimulus lights indicated food delivery followed 5 responses and resulted in responding predominately for food (1 to 3% of total responses were for the solution). Rats were exposed to solid light conditions for 0, 1, 2, 4, or 16 consecutive sessions before being re‐exposed to the flashing stimulus lights in extinction.
Results
Responding for either solution resumed when rats were re‐exposed to the flashing stimulus lights (associated with solution‐predominate responding). However, more responses occurred on the food lever with longer recent histories of responding for food instead of the solution.
Conclusions
These results suggest that the longer alternative behavior replaces drinking, the more that attention to stimuli associated with drinking decreases. These results are consistent with the notion that the risk of relapse declines with longer periods of recovery because alternative behavior comes to predominate even in the presence of stimuli associated with drinking.
•Nicotine can serve as a discriminative stimulus for ethanol-maintained responding.•In this case, nicotine and varenicline prompt ethanol responding; ethanol doesnt.•Nicotine can also serve as a ...discriminative stimulus for an alternative to ethanol.•In this case, nicotine and varenicline decrease ethanol responding.•One drug can function as discriminative stimuli to enhance use of another.
Abused drugs reinforce behavior; i.e., they increase the probability of the behavior preceding their administration. Abused drugs can also act as discriminative stimuli; i.e., they can set the occasion for responding reinforced by another event. Thus, one abused drug could come to set the occasion for the use of another and this functional relationship may play a role in polysubstance abuse, where common patterns of use could result in this relationship. Here we establish nicotine (0.4mg/kg, ip 5-min pre-session) as a discriminative stimulus for behavior reinforced by ethanol (0.1ml 8% w/v po, versus food) and determine the ability of nicotine (0.02-0.4mg/kg), varenicline (0.1-3.0mg/kg), and ethanol (250 and 500mg/kg) to control responding for ethanol. We compare these results to those from rats where nicotine signaled food was available (and ethanol was not). Nicotine came to function as a discriminative stimulus. Nicotine and varenicline produced dose-dependent increases in responding on the nicotine-appropriate lever while ethanol produced responding on the vehicle-appropriate lever. Whether this responding occurred on the lever that produced ethanol or food access depended on the training condition. These results demonstrate that a drug can come to set the occasion for use of another and suggest that this behavioral mechanism could play an important role in the maintenance of and recovery from polysubstance abuse, depending on the pattern of use.
•Addiction viewed as choice leads to useful translational models.•Delay discounting differences in monkeys influences their frequency of drug choices.•Some mice strains and adolescent mice discount ...rapidly modeling two major risk groups.•Reinforcing alternative behavior in rats reduces alcohol choices and models recovery.•Reinforcing other behavior longer reduces reinstatement by cues for ethanol taking.
Addiction may be viewed as choice governed by competing contingencies. One factor impacting choice, particularly as it relates to addiction, is sensitivity to delayed rewards. Discounting of delayed rewards influences addiction vulnerability because of competition between relatively immediate gains of drug use, e.g. intoxication, versus relatively remote gains of abstinence, e.g. family stability. Factors modifying delay sensitivity can be modeled in the laboratory. For instance, increased delay sensitivity can be similarly observed in adolescent humans and non-human animals. Similarly, genetic factors influence delay sensitivity in humans and animals. Recovery from addiction may also be viewed as choice behavior. Thus, reinforcing alternative behavior facilitates recovery because reinforcing alternative behavior decreases the frequency of using drugs. How reinforcing alternative behavior influences recovery can also be modeled in the laboratory. For instance, relapse risk decreases as abstinence duration increases, and this decreasing risk can be modeled in animals using choice procedures. In summary, addiction in many respects can be conceptualized as a problem of choice. Animal models of choice disorders stand to increase our understanding of the core processes that establish and maintain addiction and serve as a proving ground for development of novel treatments.
Background
Varenicline, a nicotinic partial agonist, selectively reduces ethanol (EtOH)‐ versus sucrose‐maintained behavior when tested in separate groups, yet like the indirect agonist fluvoxamine, ...this selectivity inverts when EtOH and food are concurrently available.
Methods
Here, we extend these findings by examining varenicline and fluvoxamine effects under a multiple concurrent schedule where food and EtOH are concurrently available in different components: Component 1 where the food fixed‐ratio was 25 and Component 2 where the food fixed‐ratio was 75. The EtOH fixed‐ratio was always 5. Food‐maintained responding predominated in Component 1, while EtOH‐maintained responding predominated in Component 2. In a second experiment, varenicline effects were assessed under a multiple schedule where food, then EtOH, then again food were available in separate 5‐minute components with fixed‐ratios of 5 for each reinforcement.
Results
In the multiple concurrent schedule, varenicline was more potent at reducing food‐ versus EtOH‐maintained responding in both components and reduced EtOH‐maintained responding more potently during Component 1 (when food was almost never earned) than in Component 2 (where food was often earned). Fluvoxamine was similarly potent at reducing food‐ and EtOH‐maintained responding. Under the multiple schedule, varenicline, like fluvoxamine, more potently decreases EtOH‐ versus food‐maintained responding when only food or EtOH is available in separate components.
Conclusions
These results demonstrate that selective effects on drug‐ versus alternative‐maintained behavior depend on the schedule arrangement, and assays in which EtOH or an alternative is the only programmed reinforcement may overestimate the selectivity of treatments to decrease EtOH self‐administration. Thus selective effects obtained under one assay may not generalize to another. Better understanding the behavioral mechanisms responsible for these results may help to guide pharmacotherapeutic development for substance use disorders.
The hypothalamus undergoes significant changes with aging and plays crucial roles in age-related metabolic alterations. Sodium-glucose co-transporter 2 inhibitors (SGLT2i) are anti-diabetic agents ...that promote glucose excretion, and metabolic homeostasis. Recent studies have shown that a SGLT2i, Canagliflozin (Cana), can extend the median survival of genetically heterogeneous UM-HET3 male mice and improve central metabolic control via increases in hypothalamic insulin responsiveness in aged males, as well as reduced age-associated hypothalamic inflammation. We studied the long- and short-term effects of Cana on hypothalamic metabolic control in UM-HET3 mice. Starting the treatment from 7 months of age, we show that 4 weeks of Cana treatment significantly reduced body weight and fat mass in male but not female mice that was associated with enhanced glucose tolerance and insulin sensitivity observed by 12 months. Indirect calorimetry showed that Cana treatment increased energy expenditure in male, but not female mice, at 12 months of age. Long-term Cana treatment increased metabolic rates in both sexes, and markedly increasing formation of both orexigenic and anorexigenic projections to the paraventricular nucleus of the hypothalamus (PVH) mostly in females by 25 months. Hypothalamic RNA-sequencing analysis revealed increased sex-specific genes and signaling pathways related to insulin signaling, glycogen catabolic pathway, neuropeptide signaling, and mitochondrial function upregulated by Cana, with males showing a more pronounced and sustained effect on metabolic pathways at both age groups. Overall, our data provide critical evidence for sex-specific mechanisms that are affected by Cana during aging suggesting key targets of hypothalamic Cana-induced neuroprotection for metabolic control.
Abstract Background Longer periods of recovery reduce the likelihood of relapse, which may be due to a reduced ability of various stimuli to occasion alcohol or drug seeking. However, this hypothesis ...remains largely uninvestigated. Methods Here we assessed the ability of intermediate stimuli to occasion responding for ethanol in rats trained to discriminate an 8 kHz tone signaling a food fixed-ratio (FR) of 5 and an ethanol FR5, from a 16 kHz tone signaling a food FR150 and ethanol FR5. In the presence of the 8 kHz tone responding for food predominates, and in the presence of the 16 kHz tone, responding for ethanol predominates. Results In the context of alternation between these conditions, varying the tone from 8 to 16 kHz produces a graded increase in ethanol (versus food) responding, consistent with a stimulus generalization function. A recent history of responding under food-predominant choice conditions, either during the test session or in the four sessions that precede it shifts the generalization function downwards. Extending this history to nine sessions shifts the curve further downwards. The stimulus generalization function was similar in a separate group, trained with different relative ratios for food and ethanol, but with similar behavioral allocation under each discriminative stimulus. Finally, withholding access to food and ethanol for 4 or 16 sessions did not affect the stimulus generalization gradient. Conclusion These results suggest that longer histories of reinforced alternative behavior might reduce the likelihood of relapse by decreasing the control exerted over alcohol- or drug-seeking by stimuli similar to those that previously occasioned alcohol- or drug-seeking.
Abstract Motivational increases due to exposure to alcohol-paired Conditioned Stimuli (CS) are central to some accounts of alcoholism. However, few studies isolate a stimulus's function as a CS from ...its other potential functions. Pavlovian-Instrumental-Transfer (PIT) procedures isolate a stimulus's function as a CS from its other functions. Though there are several relevant studies using PIT, knowledge gaps exist. Particularly, it is not clear that an alcohol-paired CS will increase alcohol seeking compared to the same stimulus in a Truly-Random-Control group, nor whether such increases are specific to alcohol seeking. To address these knowledge gaps in Experiment 1, rats responded for ethanol (0.1 ml 8% w/v) under an RI 30-sec schedule, then the lever was removed and half the rats had ethanol delivered during occasional 120-sec light presentations, while the remainder had ethanol and the light presented under independent RT schedules. Later the lever was returned and the light was presented during responding in extinction (PIT test). Following this test, levers were again removed and the light was presented without ethanol (light extinction), following again by a PIT test. Responding in the two groups during light presentations did not differ in either PIT test. Experiment 2 repeated Experiment 1 using food instead of ethanol. In Experiment 2, responding during light presentations increased in the paired group. In Experiment 3, rats were trained on a concurrent FR schedule of food and ethanol delivery. Ethanol was delivered following 5 responses and the response requirement for food adjusted so that similar numbers of food and ethanol deliveries were obtained. Subsequently, rats underwent conditioning, control and testing procedures identical to those in Experiment 1. In Experiment 3, the ethanol-paired CS increased ethanol-responding, but not food-responding. These results are most easily interpreted as changes in responding resulting from CS-elicited behavior rather than motivational changes. This interpretation is more compatible with some descriptions of the role of an alcohol-paired CS in alcoholism than others.
Cannabidiol (CBD) is a non-intoxicating phytochemical from
that is increasingly used to manage pain. The potential for CBD to ameliorate dimensional behavior symptoms occurring in multiple ...psychiatric disorders was suggested, including social interaction impairments. To test this hypothesis, adult male BTBRT+Itpr3tf/J (BTBR) mice, a model of idiopathic autism exhibiting social preference deficits and restrictive repetitive behaviors, were acutely treated with vehicle or 0.1, 1, or 10 mg/kg CBD. Social interaction preference was assessed 50 min after treatment, followed by social novelty preference at 60 min, marble burying at 75 min and social dominance at 120 min. CBD (10 mg/kg) enhanced BTBR social interaction but not social novelty preference, marble burying or dominance, with serum levels = 29 ± 11 ng/mg at 3 h post-injection. Next, acute 10 mg/kg CBD was compared to vehicle treatment in male serotonin transporter (SERT) knock-out mice, since SERT deficiency is an autism risk factor, and in their wildtype background strain controls C57BL/6J mice. CBD treatment generally enhanced social interaction preference and attenuated social novelty preference, yet neither marble burying nor dominance was affected. These findings show acute treatment with as little as 10 mg/kg purified CBD can enhance social interaction preference in male mice that are otherwise socially deficient.
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