AMP-activated protein kinase (AMPK) is a central regulator of both lifespan and health across multiple model organisms. β-Guanidinopropionic acid (GPA) is an endogenous AMPK activator previously ...shown to improve metabolic function in young and obese mice. In this study, we tested whether age of administration significantly affects the physiological outcomes of GPA administration in mice. We report that intervention starting at 7–8 months (young) results in activation of AMPK signaling and a phenotype consisting of lower body mass, improved glucose control, enhanced exercise tolerance, and altered mitochondrial electron transport chain flux similar to previous reports. When GPA treatment is started at 18–19 months (old), the effect of GPA on AMPK signaling is blunted compared to younger mice despite similar accumulation of GPA in skeletal muscle. Even so, GPA administration in older animals delayed age-related declines in lean mass, improved measures of gait performance and circadian rhythm, and increased fat metabolism as measured by respiratory exchange ratio. These results are likely partially driven by the relative difference in basal function and metabolic plasticity between young and old mice. Our results suggest that age-related declines in AMPK sensitivity may limit potential strategies targeting AMPK signaling in older subjects and suggest that further research and development is required for AMPK activators to realize their full potential.
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The number of patients seeking emergency treatment for acute synthetic cannabinoid intoxication have increased over the past decade, despite laws prohibiting their legal sale and use. ...Reported clinical signs of acute synthetic cannabinoid intoxication include tachycardia and hypertension, lethargy, confusion, agitation, hallucinations, and seizures. Clinicians have little guidance on the best course of treatment for such patients. The current standard of care involves administering benzodiazepines to sedate agitated patients and reverse seizures, antidepressants to treat anxiety reported by patients, and antipsychotics to reverse apparent psychotomimetic effects. However, the effectiveness of these treatments remains unclear. Here, in adult male C57 mice, the ability of several clinically available medications to reverse effects including hypothermia, antinociception, and ataxia of the synthetic cannabinoid JWH‐018 are examined. Additionally, effects of JWH‐018 on blood pressure and heart rate are determined, to evaluate potential cardiac effects. JWH‐018 (0.3, 1.0, or 3.0 mg/kg) or vehicle was administered 10‐min prior to test agents which included diazepam (1 & 10 mg/kg), imipramine (10 & 30 mg/kg), fluvoxamine (10 & 30 mg/kg), and haloperidol (0.3 & 3 mg/kg). Effects of these agents are compared to those of rimonabant (1 & 3 mg/kg), the CB1 antagonist. Behavioral effects were assessed immediately before, then 10, 20, 30, 40, and 50‐min after JWH‐018 administration. In other mice, cardiac effects were assessed 25–35 min after JWH‐018 administration. The potential reversal agents are administered after JWH‐018 administration because the clinical situation necessitates administration of reversal agents after cannabinoid exposure. JWH‐018 had no effect on blood pressure and only modestly decreased heart rate. As expected, JWH‐018 had dose‐dependent effects on rectal temperature, antinociception, and ataxia that persisted for at least 50‐min. Within 10–20 min of administration, rimonabant reversed hypothermic and antinociceptive effects and partially reversed ataxic effects of JWH‐018. No other agent tested affected any of the JWH‐018 effects. These results suggest that clinical reports of hypertension and tachycardia are unlikely to be due to direct effects of synthetic cannabinoids, but rather are likely due to the situation arising from intoxication requiring emergency medical care. Further, while treatment with a sedative might help calm an agitated patient, these medications are unlikely to alter the course of synthetic cannabinoid intoxication. Finally, although rimonabant was withdrawn from human use, this decision was based on adverse events during chronic rimonabant treatment for obesity. These results indicate that rimonabant or a similar drug could be useful for acute reversal of synthetic cannabinoid intoxication.
Support or Funding Information
Supported by The Department of Defense (JPC‐5) project FA8650‐15‐C‐6589
Activation of AMP activated protein kinase (AMPK) signaling has been demonstrated to extend lifespan and improve healthspan across multiple species. This suggests pharmaceutical approaches to ...increase AMPK hold the potential to modify the aging process and promote healthy aging. Beta-guanidinopropionic acid (GPA) is a naturally occurring metabolite structurally similar to creatine. GPA is capable of activating AMPK signaling in mammalian models via competitive inhibition of cytosolic creatine kinase. A previous report suggested that dietary GPA supplementation increased lifespan in Drosophila through its effect on AMPK signaling and regulation of autophagy. However, studies in Caenorhabditis have found no beneficial effect of this compound on worm lifespan and that GPA may actually diminish lifespan in at least one Caenorhabditis species. To confirm previous reports of increased longevity in Drosophila, we tested a wide range of GPA concentrations on lifespan and healthspan in both male and female W1118 flies. We report here that GPA does not extend lifespan in Drosophila as previously reported. Moreover, high doses of GPA are detrimental to Drosophila lifespan and stress resistance in male flies. These results suggest the lack of a robust effect of GPA on Drosophila lifespan and highlight the importance of replication studies within the field of aging.
► We reduce ethanol-seeking by reinforcing alternative behavior in the same context. ► The drug-associated stimulus occasioned ethanol- and food-maintained responding. ► This responding for ethanol ...decreased with longer periods of alternative reinforcement. ► Once food seeking extinguishes, ethanol-seeking resurges. ► Alternative reinforcement may decrease attention to drug-associated stimuli.
A preclinical model that includes measures of alternative behavior and drug-seeking could improve our understanding of the processes involved in successful recovery; however current preclinical models of relapse do not measure alternative behavior. We assessed the persistence of food-maintained responding and the resumption of ethanol-maintained responding after ethanol-maintained responding was reduced by changing the response requirement for concurrently available food. Ethanol (10%, w/v) was always available following 5 responses (FR5). A 16kHz tone indicating food delivery followed 150 responses (FR150) resulted in ethanol-predominate responding and substantial amounts of ethanol were earned (0.47g/kg per 30-min session) and consumed. An 8kHz tone indicating food delivery followed 5 responses (FR5) for 1, 2, 4, or 16 consecutive sessions reduced ethanol-maintained responding despite unchanged ethanol availability. Ethanol-maintained responding resumed upon subsequent presentation of the 16kHz tone. However, more responses occurred on the food lever before 5 responses occurred on the ethanol lever as the number of preceding FR5 food sessions increased. These results suggest that alternative reinforcement may reduce control by discriminative stimuli that occasion ethanol-seeking and is consistent with the risk of relapse declining with longer periods of recovery because of the strengthening of alternative behavior.
•Incubation describes greater reinstated responding in extinction after longer periods of reduced ethanol consumption.•Rats were trained to respond for ethanol and food, then ethanol consumption was ...reduced for 1 or 16 sessions either by suspending training or providing alternative reinforcement, then reinstatement was assessed in a test session where responses produced only reinforcement-paired stimuli or had no programmed consequence.•Incubation of ethanol was observed only after suspended training and when responses produced the paired stimuli.•No incubation of responding for ethanol was observed after alternative reinforcement.•These results are most consistent with incubation resulting from a degradation of control by the programmed discriminative stimuli or by the feedback function of conditioned stimuli that limit extinction responding, rather than an increase in motivation.
In reinstatement studies (a common preclinical procedure for studying relapse), incubation occurs (longer abstinence periods result in more responding). This finding is discordant with the clinical literature. Identifying determinants of incubation could aid in interpreting reinstatement and identifying processes involved in relapse. Reinstated responding was examined in rats trained to respond for ethanol and food under a multiple concurrent schedule (Component 1: ethanol FR5, food FR150; Component 2: ethanol FR5, food FR5–alternating across the 30-min session). Ethanol consumption was then reduced for 1 or 16 sessions either by suspending training (rats remained in home cage) or by providing alternative reinforcement (only Component 2 stimuli and contingencies were presented throughout the session). In the next session, stimuli associated with Component 1 were presented and responses recorded but ethanol and food were never delivered. Two test conditions were studied: fixed-ratio completion either produced ethanol- or food-associated stimuli (signaled) or had no programmed consequence (unsignaled). Incubation of ethanol responding was observed only after suspended training during signaled test sessions. Incubation of food responding was also observed after suspended training. These results are most consistent with incubation resulting from a degradation of feedback functions limiting extinction responding, rather than from increased motivation.
Genetically heterogeneous UM-HET3 mice born in 2020 were used to test possible lifespan effects of alpha-ketoglutarate (AKG), 2,4-dinitrophenol (DNP), hydralazine (HYD), nebivolol (NEBI), ...16α-hydroxyestriol (OH_Est), and sodium thiosulfate (THIO), and to evaluate the effects of canagliflozin (Cana) when started at 16 months of age. OH_Est produced a 15% increase (p = 0.0001) in median lifespan in males but led to a significant (7%) decline in female lifespan. Cana, started at 16 months, also led to a significant increase (14%, p = 0.004) in males and a significant decline (6%, p = 0.03) in females. Cana given to mice at 6 months led, as in our previous study, to an increase in male lifespan without any change in female lifespan, suggesting that this agent may lead to female-specific late-life harm. We found that blood levels of Cana were approximately 20-fold higher in aged females than in young males, suggesting a possible mechanism for the sex-specific disparities in its effects. NEBI was also found to produce a female-specific decline (4%, p = 0.03) in lifespan. None of the other tested drugs provided a lifespan benefit in either sex. These data bring to 7 the list of ITP-tested drugs that induce at least a 10% lifespan increase in one or both sexes, add a fourth drug with demonstrated mid-life benefits on lifespan, and provide a testable hypothesis that might explain the sexual dimorphism in lifespan effects of the SGLT2 inhibitor Cana.
A variety of behavioral procedures have been developed to assess cannabinoid activity in mice; however, the feasibility of establishing Delta(9)-THC as a discriminative stimulus in mice has not been ...documented.
One goal was to establish Delta(9)-THC as a discriminative stimulus in mice; after having done so, another goal was to examine the in vivo mechanism of action of Delta(9)-THC with other cannabinoids and noncannabinoids.
C57BL/6J mice (n = 8) were trained to discriminate Delta(9)-THC (10 mg/kg i.p.) from vehicle while responding under a fixed ratio 30 schedule of food presentation.
Mice satisfied the discrimination criteria in 18-98 (median = 67) sessions and the discriminative stimulus effects of Delta(9)-THC were dose-dependent (ED(50) = 2.6 mg/kg). CP 55940 and WIN 55212-2 dose-dependently increased Delta(9)-THC-appropriate responding to 100% (ED(50) = 0.032 and 0.45 mg/kg, respectively), whereas methanandamide and a variety of noncannabinoids (cocaine, ethanol, and ketamine) produced a maximum of 34% Delta(9)-THC-appropriate responding. The cannabinoid CB(1) antagonist SR 141716A (rimonabant) surmountably antagonized the discriminative effects of Delta(9)-THC, CP 55940, and WIN 55212-2; methanandamide did not significantly modify the Delta(9)-THC discriminative stimulus.
The discriminative stimulus effects of Delta(9)-THC, CP 55940, and WIN 55212-2 are mediated by the same (i.e., CB(1)) receptors, whereas the effects of methanandamide or a metabolite of methanandamide are mediated at least in part by non-CB(1) receptors. The discriminative stimulus effects of Delta(9)-THC in mice could be used to evaluate mechanisms of cannabinoid activity with approaches (e.g., inducible knockouts) currently unavailable in nonmurine species.
The recreational use of synthetic cannabinoids has recently increased. This increase is due, in part, to the recent availability of inexpensive compound sold legally online in bulk. In particular, ...JWH-018 (1-pentyl-3-(1-naphthoyl)indole) and JWH-073 (1-butyl-3-(1-naphthoyl)indole) have been found in herbal blends marketed as alternatives to cannabis. Although these particular compounds have recently been emergency scheduled in the United States, online suppliers have shifted sales to other, similar compounds that are not currently scheduled. However, the purity of the drugs obtained from online suppliers is not known. Relative purity of JWH-018 and JWH-073 from three different online suppliers was determined using high-performance liquid chromatography with ultraviolet detection and validated standards obtained from a traditional research chemical supplier. Our results show that JWH-018 and JWH-073 obtained from online vendors was of comparable purity to validated standards, even though the physical properties varied in color, texture, and odor. It is concluded that adverse events following consumption of synthetic cannabinoid preparations is unlikely to be due to impurities or residue from the manufacturing process, but rather to effects of the active drug or interactions with other psychoactive chemicals from herbs blended into products marketed as cannabis alternatives.
Abstract Long Fixed-Interval (FI) schedules, particularly second-order schedules, can engender substantial responding before drug or ethanol delivery that is uninfluenced by the direct effects of the ...drug or ethanol. Thus, these schedules can be used to study the effects of medications upon drug- or ethanol-seeking, uninfluenced by the direct effects of the self-administered drug or ethanol. Long FI second-order schedules are frequently used in primates and occasionally in rats. Under second-order schedules, completion of one response requirement, e.g., a Fixed Ratio 10 (FR10:S), produces a brief stimulus presentation, e.g., a 1-s 80-dB 4-kHZ tone, and this FR10:S serves as the response unit under another schedule, e.g., an FI 1800-s. Thus, the first FR10 completed after 1800 s would result in delivery both of the tone and of reinforcement, e.g., 10 × 0.01 mL 16% (w/v) ethanol. To examine if such schedules could be effectively used in mice, which have advantages in neurobiological and genetic studies, we trained eight C57BL/6J mice to respond under the schedule just described. This schedule maintained substantial responding. The temporal pattern of behavior was typical of an FI schedule with responding accelerating across the interval. We also examined the effects of acute and chronic administration of fluvoxamine on this responding, and these were modest. Finally, we examined responding when alcohol and/or tone deliveries were withheld, and found that extinction occurred most rapidly when both were withheld. This work demonstrates that long FI schedules of ethanol delivery may be useful in studying ethanol seeking in mice.
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