Rat breathalyzer

A Pilot Study: Treatment of High Alcohol Consumption in a Novel Minipig Model of Alcohol Use Disorder

Three medications are FDA approved in the US for treatment of Alcohol Use Disorder (AUD), and a few others are used off-label. Patient compliance and efficacy in the broader population are major hurdles for current AUD medications. As a consequence, there is an urgent need for improved pharmacotherapeutics to complement behavioral approaches. Here, we report pilot testing of a minocycline analog, 10-butylether minocycline (BEM, 10 mg/kg p.o.), in two female minipigs with free-choice drinking to intoxication for nearly two and a half years. Each pig met DSM-5 criteria for diagnosis of severe AUD, and BEM reduced both alcohol intake and preference. BEM is currently undergoing testing for approval as an Investigational New Drug by the FDA for AUD treatment.

A New Method for Breath and Blood Alcohol Determination in Rats Using a Breath Alcohol Meter: An Experimental Study

Background

The use of police breath alcohol detectors in rat breath alcohol detection experiments has always been a challenge because of the small lung capacity and inability of rats to actively inhale. However, the method of using gas chromatography to detect blood alcohol concentration is time-consuming, complex, relatively expensive, and cannot achieve on-site detection and multi-point unlimited non-invasive detection.

Objectives

In this study, a laboratory method was validated for rat breath ethanol concentration (BrAC) measurement to estimate blood ethanol concentration (BAC) in rats.

Methods

The rats were placed in a gas collection bottle, the breath sample was drawn out with a syringe, and injected into the mouthpiece of the breath alcohol detector through a rubber tube. The results were immediately detected and automatically converted to BAC. Male rats were randomly divided into three groups. The control group received an intraperitoneal injection of normal saline, the liver injury group received an intraperitoneal injection of 50% Carbon tetrachloride (CCL4 1 mL.kg^-1), and the induction group received an intraperitoneal injection of phenobarbital sodium (75 mg.kg^-1). Western blot analysis was used to detect the protein expression of CYP2E1. Similar grouping and experimental methods were used for female rats.

Results

This method was reproducible. The metabolic activity of CYP2E1 was downregulated in the injury group and upregulated in the induction group, which was consistent with the results obtained for CYP2E1 protein expression.

Conclusions

Our results confirmed that the rat gas cylinder breath alcohol assay can be used for multiple detections with immediate and non-invasive determination of alcohol metabolizing capacity. This is important for studies that require repeated assessment of blood alcohol levels.

Drug effects on multiple and concurrent schedules of ethanol- and food-maintained behaviour: context-dependent selectivity

BACKGROUND AND PURPOSE

Drugs that more potently or effectively reduce ethanol-maintained behaviour versus an alternative are considered selective and are considered promising pharmacotherapies for alcoholism. Such results are often obtained using separate groups or multiple schedules where ethanol and the alternative are available alone or sequentially. Recently, we observed that when ethanol and food were available sequentially under a multiple schedule, fluvoxamine and varenicline were selective; yet this selectivity disappeared when ethanol and food were concurrently available.

EXPERIMENTAL APPROACH

We examined the generality of these findings by comparing doses of several drugs required to decrease ethanol- and food-maintained responding under a multiple schedule and under a concurrent schedule. Effects were determined for chlordiazepoxide, 2,5-dimethoxy-4-iodoamphetamine (DOI), meta-chlorophenylpiperazine (mCPP), morphine, naltrexone and d-amphetamine.

KEY RESULTS

Under the multiple schedule, ED50 values for decreases in ethanol-maintained responding were significantly different and lower than ED50 s for decreases in food-maintained responding (demonstrating selectivity) for each drug except for chlordiazepoxide (which was equipotent) and naltrexone (which did not affect responding). However, this selectivity vanished or even inverted under the concurrent schedule, such that ED50 values for decreasing ethanol- and food-maintained responding were not different (or, following DOI, the ED50 for food-maintained responding was lower than for ethanol-maintained responding).

CONCLUSIONS AND IMPLICATIONS

Results are consistent with those seen following fluvoxamine and varenicline administration, and suggest that selectivity is assay-dependent. These results indicate the need for careful interpretation of selective drug effects, especially when obtained in situations where ethanol or the alternative is the only programmed reinforcement available.

A history of alternative reinforcement reduces stimulus generalization of ethanol-seeking in a rat recovery model

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.

Reinforcement of an alternative behavior as a model of recovery and relapse in the rat

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 16 kHz tone indicating food delivery followed 150 responses (FR150) resulted in ethanol-predominate responding and substantial amounts of ethanol were earned (0.47 g/kg per 30-min session) and consumed. An 8 kHz 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 16 kHz 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.

Effects of varenicline on ethanol- and food-maintained responding in a concurrent access procedure

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.

Shifts in discriminative control with increasing periods of recovery in the rat

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.

Ethanol consumption: how should we measure it? Achieving consilience between human and animal phenotypes

There is only modest overlap in the most common alcohol consumption phenotypes measured in animal studies and those typically studied in humans. To address this issue, we identified a number of alcohol consumption phenotypes of importance to the field that have potential for consilience between human and animal models. These phenotypes can be broken down into three categories: (1) abstinence/the decision to drink or abstain; (2) the actual amount of alcohol consumed; and (3) heavy drinking. A number of suggestions for human and animal researchers are made in order to address these phenotypes and enhance consilience. Laboratory studies of the decision to drink or to abstain are needed in both human and animal research. In human laboratory studies, heavy or binge drinking that meets cut-offs used in epidemiological and clinical studies should be reported. Greater attention to patterns of drinking over time is needed in both animal and human studies. Individual differences pertaining to all consumption phenotypes should be addressed in animal research. Lastly, improved biomarkers need to be developed in future research for use with both humans and animals. Greater precision in estimating blood alcohol levels in the field, together with consistent measurement of breath/blood alcohol levels in human laboratory and animal studies, provides one means of achieving greater consilience of alcohol consumption phenotypes.

Ethanol increases the distribution of MDMA to the rat brain: possible implications in the ethanol-induced potentiation of the psychostimulant effects of MDMA

Ecstasy (3,4-methylenedioxymethylamphetamine; MDMA) is a popular club drug often taken with ethanol (EtOH). We recently found EtOH potentiated the psychomotor effects of MDMA in rats. This potentiation could reflect pharmacodynamic or/and pharmacokinetic processes. To test the latter hypothesis, rats were injected i.p. with 6.6 or 10 mg/kg MDMA with or without 1.5 g/kg EtOH, and were killed at 5, 15 or 60 min after injection. MDMA, its primary metabolite, 3,4-methylenedioxyamphetamine (MDA), and EtOH concentrations were determined in the plasma and the hippocampus, frontal cortex and striatum at each time-point. EtOH potentiated MDMA-induced hyperactivity mainly during the first 60 min post-administration. Fifteen and 60 min after treatment with MDMA and EtOH, MDMA concentrations were greater than after MDMA alone in the blood and the three brain regions examined. EtOH, however, did not increase the fraction of MDMA converted to MDA, as shown by unaltered MDA/MDMA ratios at either MDMA dose. Interestingly, when combined with EtOH, the distribution of MDMA and MDA in the brain was not homogeneous. Concentrations of both were much higher in the striatum and cortex, than in the hippocampus. Thus, at least part of the potentiation of the MDMA-induced hyperlocomotion by EtOH might be the result of a higher concentration of MDMA and metabolites in the blood and brain. Our results present clear evidence that EtOH increases brain and blood concentrations of MDMA and leads to the possibility of both enhanced MDMA-based neurotoxicity and increased liability for abuse.

Mouse breathalyzer

BACKGROUND

The development of a relatively simple, noninvasive method for estimating blood ethanol concentrations in mice will be useful in behavioral studies related to alcoholism. This study validated such a method.

METHODS

The apparatus consists of a body chamber fitted with a head stock through which the mouse head protrudes. This was fitted against a water-jacketed head-space chamber surrounding the mouse's head. Rebreathed air maintained at 37 degrees C in the head-space chamber was removed using a peristaltic pump and loaded into a 1-ml injection loop. Ethanol in the sample was quantified using gas chromatography. To validate this method, ethanol levels in breath samples were compared against those in tail blood samples collected immediately after the breath samples. Breath samples were collected at 5, 10, 20, 40, 80, 120, and 160 minutes after ethanol (0.4, 0.8, 1.2, 1.6, 2.4, and 3.2 g/kg) was administered to male C57BL/6J mice.

RESULTS

Breath and blood ethanol levels were well correlated (r(2) = 0.96) across time points on the descending ethanol-time curve at doses below 2.4 g/kg. Correlation for these doses on the ascending portion of the curve had greater variance, but was still well correlated (r(2) = 0.92).

CONCLUSIONS

The mouse breathalyzer is an accurate, convenient, noninvasive and well-tolerated method for estimating blood ethanol concentrations in mice across a range of behaviorally relevant concentrations below 2.4 g/kg, especially on the descending limb of the ethanol-time curve. Although this procedure requires a gas chromatograph in the animal facility, the ability to estimate ethanol concentrations quickly and easily will be especially useful in behavioral studies where repeated blood sampling is not feasible.

Acute tolerance to rate-decreasing effects of single doses of ethanol

Acute tolerance occurs when behavioral impairment is greater at a given blood ethanol concentration (BAC) on the ascending versus descending limb of the BAC-time curve following administration of a single dose of ethanol, however studies utilizing learned behaviors have not been widely reported. We assessed acute tolerance to single doses of ethanol in five Lewis rats responding under a fixed-ratio (FR8) schedule of food presentation. Response rates for food during 1-min components (ending 2, 4, 11, 18, 33, and 57 min after ethanol administration) were determined, and BAC was measured immediately after each component using a rat breathalyzer. Ethanol (0.4, 0.6, 0.8, and 1.2 g/kg, i.p.) produced dose-related decreases in responding for food that tended to recover over time for all but the highest dose tested. Similarly, dose-related increases in BAC were also observed. Using either an analysis that expressed impairment per unit BAC on the ascending limb versus the descending limb (by assessing the area under the curve (AUC) for behavior and BAC on each limb), the slope of the function that relates the behavioral effect to BAC (each expressed as percent maximum effect), or a variant of the Mellanby method (hysteresis), acute tolerance was observed following a dose of 0.4 g/kg ethanol. Though behavior appeared to recover on the descending limb following higher doses (especially 0.6 and 0.8 g/kg), acute tolerance to these doses was not present.