Cocaine and alcohol interactions in the rat: effect on cocaine pharmacokinetics and pharmacodynamics

Is there a relationship between abuse of alcohol and illicit drugs seen in hair results?

Combined use of alcohol and illicit drugs is a serious health and social problem. In this study, it was examined, whether a relationship between alcohol and drug abuse can be ascertained by comparison of alcohol marker and drug concentrations in hair. In the frame of a social support system for families with parental abuse of illicit drugs, hair samples were analyzed between 2011 and 2022 for methadone, heroin (6-acetylmorphine), cocaine, amphetamine, ecstasy (MDMA), cannabinoids (THC), and the alcohol markers ethyl glucuronide (EtG) and ethyl palmitate (EtPa). For 1314 hair samples from adolescent and adult family members, the hair results show a prevalence of combined occasional or regular drug use and social or abusive alcohol use of 41%-60% except heroin (35%). The drug concentrations were statistically compared in the three categories of abstinence or moderate drinking, social drinking, and alcohol abuse. For the most frequently detected drug cocaine (n = 703), a significant increase of the concentrations with rising alcohol consumption was found. The frequent detection of cocaethylene proved the preferred simultaneous intake of both substances. For THC (n = 489), no significant difference between the alcohol consumer groups was seen. Concerning the less frequently detected methadone (n = 89), 6-acetylmorphine (n = 92), amphetamine (n = 123), and MDMA (n = 105), no clear trend between drug and alcohol marker results was determined. It is concluded that the evaluation of hair results is an appropriate way to study the extent of combined drug-alcohol consumption and complements other studies based on acquisition of consumption data by interview or questionnaire.

Cocaine addicted rats show reduced neural activity as revealed by manganese-enhanced MRI

Cocaine addiction develops as a continuum from recreational to habitual and ultimately compulsive drug use. Cocaine addicts show reduced brain activity. However, it is not clear if this condition results from individual predisposing traits or is the result of chronic cocaine intake. A translational neuroimaging approach with an animal model distinguishing non-addict-like vs. addict-like animals may help overcome the limitations of clinical research by comparing controlled experimental conditions that are impossible to obtain in humans. Here we aimed to evaluate neuronal activity in freely moving rats by manganese enhanced magnetic resonance imaging in the 0/3crit model of cocaine addiction. We show that addict-like rats exhibit reduced neuronal activity compared to cocaine-naïve controls during the first week of abstinence. In contrast, cocaine-experienced non-addict-like rats maintained their brain activity at a level comparable to cocaine-naïve controls. We also evaluated brain activity during cocaine bingeing, finding a general reduction of brain activity in cocaine experienced rats independent of an addiction-like phenotype. These findings indicate that brain hypoactivity in cocaine addiction is associated with the development of compulsive use rather than the amount of cocaine consumed, and may be used as a potential biomarker for addiction that clearly distinguishes non-addict-like vs addict-like cocaine use.

Cross-reinstatement between 3,4-methylenedioxypyrovalerone (MDPV) and cocaine using conditioned place preference

3,4-Methylenedioxypyrovalerone (MDPV) is a new psychoactive substance (NPS) considered to be a cocaine-like psychostimulant. The substitution of an established illicit drug as cocaine with an NPS is a pattern of use reported among drug users. The aim of this study was to investigate the relationship between cocaine and MDPV in the reinstatement of the conditioned place preference (CPP) paradigm, in order to establish whether there is cross-reinstatement between the two psychostimulants. Four experimental groups of male OF1 mice were subjected to the CPP paradigm: MDPV-MDPV, Cocaine-Cocaine, Cocaine-MDPV, and MDPV-Cocaine. The first drug refers to the substance with which the animals were conditioned (cocaine 10 mg/kg or MDPV 2 mg/kg) and the s to the substance with which preference was reinstated. In parallel, G9a, ΔFosB, CB1 receptor, CDK5, Arc and c-Fos were determined in ventral striatum. MDPV induced CPP at doses from 1 to 4 mg/kg. Although 2 mg/kg MDPV induced a stronger psychostimulant effect than 10 mg/kg cocaine, both doses seemed to be equivalent in their rewarding properties. However, memories associated with MDPV required more time to be extinguished. MDPV and cocaine restore drug-seeking behavior with respect to each other, although relapse into drug-taking is always more pronounced with the conditioning drug. The fact that MDPV-treated mice show increased ΔFosB protein levels correlates with its longer extinction time and points to the activation of neuroplasticity mechanisms that persist for at least 12 days. Moreover, in these animals, a priming-dose of cocaine can trigger significant neuroplasticity, implying a high vulnerability to cocaine abuse.

Catalytic activities of cocaine hydrolases against the most toxic cocaine metabolite norcocaethylene

A majority of cocaine users also consume alcohol. The concurrent use of cocaine and alcohol produces the pharmacologically active metabolites cocaethylene and norcocaethylene, in addition to norcocaine. Both cocaethylene and norcocaethylene are more toxic than cocaine itself. Hence, a truly valuable cocaine-metabolizing enzyme for cocaine abuse/overdose treatment should be effective for the hydrolysis of not only cocaine, but also its metabolites norcocaine, cocaethylene, and norcocaethylene. However, there has been no report on enzymes capable of hydrolyzing norcocaethylene (the most toxic metabolite of cocaine). The catalytic efficiency parameters (kcat and KM) of human butyrylcholinesterase (BChE) and two mutants (known as cocaine hydrolases E14-3 and E12-7) against norcocaethylene have been characterized in the present study for the first time, and they are compared with those against cocaine. According to the obtained kinetic data, wild-type human BChE showed a similar catalytic efficiency against norcocaethylene (kcat = 9.5 min-1, KM = 11.7 μM, and kcat/KM = 8.12 × 105 M-1 min-1) to that against (-)-cocaine (kcat = 4.1 min-1, KM = 4.5 μM, and kcat/KM = 9.1 × 105 M-1 min-1). E14-3 and E12-7 showed an improved catalytic activity against norcocaethylene compared to wild-type BChE. E12-7 showed a 39-fold improved catalytic efficiency against norcocaethylene (kcat = 210 min-1, KM = 6.6 μM, and kcat/KM = 3.18 × 107 M-1 min-1). It has been demonstrated that E12-7 as an exogenous enzyme can efficiently metabolize norcocaethylene in rats.

Sequential cocaine-alcohol self-administration produces adaptations in rat nucleus accumbens core glutamate homeostasis that are distinct from those produced by cocaine self-administration alone

There are currently no FDA-approved medications to reduce cocaine relapse. The majority of preclinical studies aimed at identifying the neurobiology underlying relapse involve the self-administration of cocaine alone, whereas many, if not a majority, of cocaine users engage in polysubstance use. Here we developed a rat model of sequential cocaine and alcohol self-administration to test the hypothesis that this combination produces distinct neuroadaptations relative to those produced by cocaine alone. Male rats underwent intravenous cocaine self-administration (2 h/day) followed by 6 h access to unsweetened alcohol (20% v/v) for 12 days. After extinction training, we assessed surface expression of the glutamate transporter GLT-1 and glutamate efflux in the nucleus accumbens (NA) core during the reinstatement of cocaine-seeking. We also tested the ability of ceftriaxone to attenuate the reinstatement of cocaine-seeking and assessed reinstatement-induced Fos expression in several regions critical for reinstatement. Alcohol consumption did not alter cocaine intake, nor did access to cocaine alter alcohol consumption. However, we noted significant changes in glutamate homeostasis in the NA core of cocaine + alcohol rats relative to rats consuming cocaine alone, such as increased surface GLT-1 expression and a lack of increase in glutamate efflux during reinstatement of cocaine-seeking. A history of cocaine + alcohol also altered patterns of reinstatement-induced Fos expression. These changes likely account for the inability of ceftriaxone to attenuate cocaine relapse in cocaine + alcohol rats, while it does so in rats consuming only cocaine. As such glutamate neuroadaptations are targeted by medications to reduce cocaine relapse, preclinical models should consider polysubstance use.

Alcohol Interaction with Cocaine, Methamphetamine, Opioids, Nicotine, Cannabis, and γ-Hydroxybutyric Acid

Millions of people around the world drink alcoholic beverages to cope with the stress of modern lifestyle. Although moderate alcohol drinking may have some relaxing and euphoric effects, uncontrolled drinking exacerbates the problems associated with alcohol abuse that are exploding in quantity and intensity in the United States and around the world. Recently, mixing of alcohol with other drugs of abuse (such as opioids, cocaine, methamphetamine, nicotine, cannabis, and γ-hydroxybutyric acid) and medications has become an emerging trend, exacerbating the public health concerns. Mixing of alcohol with other drugs may additively or synergistically augment the seriousness of the adverse effects such as the withdrawal symptoms, cardiovascular disorders, liver damage, reproductive abnormalities, and behavioral abnormalities. Despite the seriousness of the situation, possible mechanisms underlying the interactions is not yet understood. This has been one of the key hindrances in developing effective treatments. Therefore, the aim of this article is to review the consequences of alcohol's interaction with other drugs and decipher the underlying mechanisms.

Kinetic characterization of human butyrylcholinesterase mutants for the hydrolysis of cocaethylene

It is known that the majority of cocaine users also consume alcohol. Alcohol can react with cocaine to produce a significantly more cytotoxic compound, cocaethylene. Hence a truly valuable cocaine-metabolizing enzyme as treatment for cocaine abuse/overdose should be efficient for not only cocaine itself, but also cocaethylene. The catalytic parameters (kcat and KM) of human BChE (butyrylcholinesterase) and two mutants (known as cocaine hydrolases E14-3 and E12-7) for cocaethylene are characterized in the present study, for the first time, in comparison with those for cocaine. On the basis of the obtained kinetic data, wild-type human BChE has a lower catalytic activity for cocaethylene (kcat=3.3 min(-1), KM=7.5 μM and kcat/KM=4.40 × 10(5) M(-1)·min(-1)) compared with its catalytic activity for (-)-cocaine. E14-3 and E12-7 have a considerably improved catalytic activity against cocaethylene compared with the wild-type BChE. E12-7 is identified as the most efficient enzyme for hydrolysing cocaethylene in addition to its high activity for (-)-cocaine. E12-7 has an 861-fold improved catalytic efficiency for cocaethylene (kcat=3600 min(-1), KM=9.5 μM and kcat/KM=3.79 × 10(8) M(-1)·min(-1)). It has been demonstrated that E12-7 as an exogenous enzyme can indeed rapidly metabolize cocaethylene in rats. Further kinetic modelling has suggested that E12-7 with an identical concentration as that of the endogenous BChE in human plasma can effectively eliminate (-)-cocaine, cocaethylene and norcocaine in simplified kinetic models of cocaine abuse and overdose associated with the concurrent use of cocaine and alcohol.

Effect of the single or combined administration of cocaine and testosterone on cardiovascular function and baroreflex activity in unanesthetized rats

Abuse of cocaine and androgenic-anabolic steroids has become a serious public health problem. Despite reports of an increase in the incidence of simultaneous illicit use of these substances, potential toxic interactions between cocaine and androgenic-anabolic steroids in the cardiovascular system are unknown. In the present study, we investigated the effect of single or combined administration of testosterone and cocaine for 1 or 10 consecutive days on basal cardiovascular parameters, baroreflex activity, and hemodynamic responses to vasoactive agents in unanesthetized rats. Ten-day combined administration of testosterone and cocaine increased baseline arterial pressure. Changes in arterial pressure were associated with altered baroreflex activity and impairment of both hypotensive response to intravenous sodium nitroprusside and pressor effect of intravenous phenylephrine. Chronic single administration of either testosterone or cocaine did not affect baseline arterial pressure. However, testosterone-treated animals presented rest bradycardia, cardiac hypertrophy, alterations in baroreflex activity, and enhanced response to sodium nitroprusside. Repeated administration of cocaine affected baroreflex activity and impaired vascular responsiveness to both sodium nitroprusside and phenylephrine. One-day single or combined administration of the drugs did not affect any parameter investigated. In conclusion, the present results suggest a potential interaction between toxic effects of cocaine and testosterone on the cardiovascular activity. Changes in baseline arterial pressure after combined administration of these 2 drugs may result from alterations in baroreflex activity and impairment of vascular responsiveness to vasoactive agents.

Patients with detectable cocaethylene are more likely to require intensive care unit admission after trauma

Cocaethylene (CE) is a toxic metabolite that is formed after simultaneous consumption of cocaine and ethanol. This potent stimulant is more toxic than cocaine and has a longer half-life. The deleterious hemodynamic and cardiovascular effects of CE have been proven in animal models. The aim of this study is to assess the impact of CE on clinical outcomes after trauma. We prospectively enrolled adult (≥13 years) trauma patients requiring admission. Predictor variables were age, sex, mechanism of injury, Injury Severity Score, base deficit, and toxicology groups (ethanol alone, cocaine alone, CE, and none). The outcomes examined were mortality, intensive care unit (ICU) admission, and length of hospital stay (LOS). We used nonparametric tests to compare continuous variables and χ² test to compare categorical data. We constructed a logistic regression to identify variables that could predict mortality and ICU admission. We enrolled 417 patients (74% male; 70% blunt injury; median age, 40 [range, 13-95]; overall mortality, 2.2%). Urine toxicology and serum ethanol level screens classified patients into the following groups: 13.4% ethanol only, 4.1% cocaine only, 8.9% CE, and 46% none. Mortality and LOS were not statistically different among the groups. In logistic regression analysis, none of the variables were statistically significant in predicting mortality. However, the presence of CE significantly increased the likelihood of ICU admission (odds ratio, 5.9; 95% confidence interval, 1.6-22). The presence of detectable CE in the urine does not increase the mortality or LOS in trauma patients requiring admission but does increase the likelihood of ICU admission.

Fentanyl, but not haloperidol, entrains persisting circadian activity episodes when administered at 24- and 31-h intervals

Administration of several drugs of abuse on a 24-h schedule has been shown to entrain both pre-drug (anticipatory) and post-drug (evoked) circadian activity episodes that persist for several days when the drug is withheld. The present study tested the entrainment effects of fentanyl, an opioid agonist with a noted abuse liability, and haloperidol, an anti-psychotic dopamine antagonist without apparent abuse liability. Adult female Sprague-Dawley rats housed under constant light in cages with attached running wheels received repeated low, medium, or high doses of either fentanyl or haloperidol on a 24-h administration schedule followed by a 31-h schedule (Experiment 1) or solely on a 31-h schedule (Experiment 2). The results showed that all three doses of fentanyl entrained both pre-drug and post-drug episodes of wheel running when administered every 24h, and the combined pre- and post-fentanyl activity episodes persisted for at least 3 days when the drug was withheld during test days. On the 31-h schedule, fentanyl produced an "ensuing" activity episode approximately 24h post-administration, but failed to produce an anticipatory episode 29-31h post-administration. In contrast, haloperidol injections failed to produce both pre-drug episodes on the 24-h schedule and circadian ensuing episodes on the 31-h schedule, and post-haloperidol suppression of activity appeared to mask the free-running activity rhythm. Taken together, these results provide additional evidence that drugs of abuse share a common ability to entrain circadian activity episodes.

Pharmacodynamic evaluation of the cardiovascular effects after the coadministration of cocaine and ethanol

One of the most common drug dependencies occurring with alcoholism is cocaine dependence. This combination is particularly worrisome because of the increased risk of cardiovascular events associated with their coabuse. Although it is well known that ethanol increases the cardiovascular effects of cocaine by inhibiting cocaine clearance and the formation of cocaethylene, it has also been postulated that ethanol enhances the cardiovascular effects of cocaine independent of the two latter mechanisms. In this study, we investigated the cardiovascular pharmacodynamics of the cocaine-ethanol interaction to determine whether ethanol directly enhanced the cardiovascular effects of cocaine. Dogs (n = 6) were administered cocaine alone (3 mg/kg i.v.) and in combination with ethanol (1 g/kg i.v.) on separate study days. Blood pressure, heart rate, and the electrocardiogram were monitored continuously, and blood samples were collected periodically after drug administration. Concentration-time data were fitted to a two-compartment model, and concentration-effect data were fitted to a simple E(max) model using WinNonlin software. Pharmacokinetic and pharmacodynamic parameters were compared between the two treatment phases by a paired t test. The administration of ethanol before cocaine resulted in a decrease in cocaine clearance, but there were no differences in any of the other pharmacokinetic or pharmacodynamic parameter values between the cocaine alone and cocaine plus ethanol phases. As has been demonstrated in previous animal and human studies, the clearance of cocaine was decreased by prior administration of ethanol. However, ethanol did not change the concentration-effect relationship of the cardiovascular response to cocaine administration. It is concluded from this study that ethanol does not directly enhance the cardiovascular effects of cocaine.

Prediction of Drug Tissue to Plasma Concentration Ratios Using a Measured Volume of Distribution in Combination With Lipophilicity

One of the drug specific parameters needed in physiologically based pharmacokinetic (PBPK) models is the tissue to plasma drug concentration ratios (K(p) values). The aim of this study was to develop an empirical method for predicting K(p) values using a preclinically determined in vivo volume of distribution, in combination with descriptors for drug lipophilicity. Pharmacokinetic data in laboratory animals for a wide range of drug compounds were collected. Obtained correlations between K(p) values for muscle and other tissues, in a training set of 49 compounds, were used to predict K(p) values for a test set of 22 compounds, based on their volume of distribution and lipophilicity. Predicted K(p) values agreed well with experimentally determined values (n = 118), especially for noneliminating tissues (r(2) = 0.81) with 72% and 87% being within a factor +/-2 and +/-3, respectively. In conclusion, we present an empirical method based on a measured volume of distribution and a drug lipophilicity descriptor, which can be used to predict tissue K(p) values with reasonable accuracy.

Interactions between ethanol and cocaine, amphetamine, or MDMA in the rat: thermoregulatory and locomotor effects

RATIONALE

(+/-)-3,4-methylenedioxymethamphetamine (MDMA, ecstasy) is often taken recreationally with ethanol (EtOH). In rats, EtOH may potentiate MDMA-induced hyperactivity, but attenuate hyperthermia.

OBJECTIVE

Experiment 1 compared the interactions between EtOH (1.5 g/kg) and MDMA (6.6 mg/kg) with EtOH + cocaine (COCA; 10 mg/kg) and EtOH + amphetamine (AMPH; 1 mg/kg) on locomotor activity and thermoregulation. Experiment 2 used a weaker dose of MDMA (3.3 mg/kg) and larger doses of COCA (20 mg/kg) and AMPH (2 mg/kg).

MATERIALS AND METHODS

Drug treatments were administered on four occasions (2, 5, and 2 days apart, respectively; experiment 1) or two (2 days apart; experiment 2).

RESULTS

All psychostimulants increased activity, and EtOH markedly increased the effect of MDMA. AMPH alone-related hyperactivity showed modest sensitization across treatment days, while MDMA + EtOH activity showed marked sensitization. AMPH, COCA, and MDMA induced hyperthermia of comparable amplitude (+1 to +1.5 degrees C). Co-treatment with EtOH and AMPH (1 mg/kg) or COCA (10 mg/kg) produced hypothermia greater than that produced by EtOH alone. Conversely, EtOH attenuated MDMA-related hyperthermia, an effect increasing across treatment days. These results demonstrate that the interaction between MDMA and EtOH may be different from the interaction between EtOH and AMPH or COCA.

CONCLUSION

Because of potential health-related consequences of such polydrug misuse, it is worth identifying the mechanisms underlying these interactions, especially between EtOH and MDMA. Given the different affinity profiles of the three drugs for serotonin, dopamine, and norepinephrine transporters, our results appear compatible with the possibility of an important role of serotonin in at least the EtOH-induced potentiation of MDMA-induced hyperlocomotion.

Ethanol–ecstasy (MDMA) interactions in rats: Preserved attenuation of hyperthermia and potentiation of hyperactivity by ethanol despite prior ethanol treatment

Recreational use of ecstasy, or (+/-)-3,4-methylenedioxymethamphetamine (MDMA), is often associated with other drugs, among which ethanol is one of the most common. Little is known, however, about the interaction between these two drugs. Using a daily ethanol and/or MDMA administration regimen, we recently showed that ethanol potentiated the hyperactivity (in the home cage), but attenuated the hyperthermia induced by MDMA. The prevention of hyperthermia occurred only on the first of four daily ethanol-MDMA treatments, indicating possible tolerance to ethanol. In order to test the tolerance hypothesis, we treated Long-Evans adult male rats with ethanol on 4 consecutive days prior to their first treatment with MDMA-ethanol. Our results first confirmed that ethanol (1.5 g/kg, i.p.) potentiates the psychomotor effects of MDMA (10 mg/kg, i.p.), while attenuating its pyretic effects (6.6 mg/kg, i.p.). The results also showed that both the potentiation of locomotor activity and the attenuation of hyperthermia by ethanol are not at all altered by prior ethanol treatment. This indicates that tolerance to ethanol per se does not account for what appears to be tolerance to the ethanol-MDMA combination, thus indicating that ethanol-MDMA combination likely has unique pharmacological effects.

Effects of systemically administered cocaine on sensory responses to peri-threshold vibrissae stimulation: individual cells, ensemble activity, and animal behaviour

Previous studies have shown that systemic administration of cocaine transiently alters stimulus-evoked responses of ventral posteromedial (VPM) thalamic neurons. Results from these single-unit electrophysiological studies revealed that cocaine was equally likely to augment or attenuate the magnitude of sensory evoked responses following threshold level stimulation of peripheral receptive fields. In an attempt to clarify the impact of cocaine administration on sensory signal processing, we examined the drug's effects on responses of individual neurons and ensembles of VPM thalamic neurons to sensory stimuli, and performance of subjects in a sensory detection behavioural task. Extracellular responses of single (n = 1 cell/rat) or multiple VPM thalamic neurons (n = 10-40 cells/rat) were monitored before and after cumulative doses of cocaine (0.25-2.0 mg/kg i.v.). Neuronal responses were characterized by assessing the response profile to a range of peri-threshold-level deflections of the optimal whisker on the contralateral face. Drug effects on stimulus-response curves, determined from quantitative analysis of spike train data, indicated that whereas cocaine elicits variable effects at the single cell level, the stimulus-evoked response of the recorded population was likely to increase following lower (0.25-1.0 mg/kg i.v.) doses of cocaine. Furthermore, cocaine preferentially enhanced responses to smaller magnitude deflections of vibrissa, altering the response profile from a mode that accurately conveyed stimulus strength to one that increased detection at the expense of discrimination. Finally, a similar pattern emerged in a behavioural paradigm involving rats trained to detect variable amplitude whisker pad stimulation, suggesting a common action of cocaine that may contribute to the drug's addictive properties.

The effects of cocaine, alcohol and cocaine/alcohol combinations in conditioned taste aversion learning

We have recently reported that alcohol attenuates cocaine place preferences. Although the basis for this effect is unknown, alcohol may attenuate cocaine reward by potentiating its aversive effects. To examine this possibility, these experiments assessed the effects of alcohol on cocaine-induced taste aversions under conditions similar to those that resulted in attenuated place preferences. Specifically, Experiments 1 and 2 assessed the effects of alcohol (0.5 g/kg) on taste aversions induced by 20, 30 and 40 mg/kg cocaine. Experiment 3 examined the role of intertrial interval in the effects of alcohol (0.5 g/kg) on cocaine (30 mg/kg) taste aversions. In Experiments 1 and 2, cocaine was effective at conditioning aversions. Alcohol produced no measurable effect. Combining cocaine and alcohol produced no greater aversion than cocaine alone (and, in fact, weakened aversions at the lowest dose of cocaine). In Experiment 3, varying the intertrial interval from 3 days (as in the case of Experiments 1 and 2) to 1 day (a procedure identical to that in which alcohol attenuated cocaine place preferences) resulted in significant alcohol- and cocaine-induced taste aversions. Nonetheless, alcohol remained ineffective in potentiating cocaine aversions. Thus, under these conditions alcohol does not potentiate cocaine's aversiveness. These results were discussed in terms of their implication for the effects of alcohol on cocaine-induced place preferences. Further, the effects of alcohol on place preferences conditioned by cocaine were discussed in relation to other assessments of the effects of alcohol on the affective properties of cocaine and the implications of these interactions for alcohol and cocaine co-use.

Cerebral perfusion defects in combined cocaine and alcohol dependence

BACKGROUND

Cocaine abuse has been associated with widely distributed areas of significant cerebral blood flow (CBF) reductions or hypo-perfusion as well as CBF hyper-perfusion, but these perfusion abnormalities have not been examined using newer technologies such as statistical parametric mapping (SPM). These areas of abnormal CBF may be more likely among those who abuse cocaine and alcohol together.

METHODS

Using SPECT with HMPAO for CBF we compared proportional scaling (PS) to histogram normalization (HEQ) in SPM among 20 controls and 32 recently abstinent cocaine abusers. We then separated the cocaine abusers into two groups (12 cocaine plus alcohol abusers and 20 cocaine alone abusers) and compared both groups to the 20 controls for brain areas of hypo- and hyper-perfusion.

RESULTS

Sensitivity to hypo-perfusion was greater with HEQ than PS. Hypo-perfused areas were more likely in the 12 alcohol plus cocaine abusers than in the 20 cocaine alone abusers or 20 controls, and hyper-perfused areas were significantly more likely among the cocaine abusers than controls. The type of CBF abnormality varied by brain location with hypo-perfusion significantly more likely in occipital and temporal cortex or cerebellum and hyper-perfusion more likely in frontal and parietal cortex.

CONCLUSIONS

These abnormalities in brain perfusion are consistent with previous non-SPM approaches that showed more hypo-perfusion in cocaine abusers than controls and appear to reflect vasospasm and potential compensations in cerebral blood flow.

Ethanol administration potentiates cocaine-induced dopamine levels in the rat nucleus accumbens

Ethanol and cocaine are frequently co-abused, and the drug combination has been reported to produce an increased and prolonged subjective euphoria as compared to when either drug is administered alone. Acute administration of ethanol or cocaine increases the extracellular dopamine (DA) concentration in the nucleus accumbens (NAcc), a terminal region of the mesolimbic dopaminergic pathway. In the present study, the effects of separate and concurrent administration of cocaine and ethanol on DA concentrations in the NAcc were studied in rats pretreated with ethanol. Four groups of rats received either ethanol (2 g/kg, i.p.) or saline twice daily for 6 consecutive days. Thereafter, rats were given injections of saline or cocaine for another 2 days (i.e. treatment days 7 and 8) using a 'binge' administration pattern (three i.p. injections of 15 mg/kg each with 1-h interval starting 40 min after the first of the two daily doses of ethanol/saline). Stereotypic behavior was scored after each 'binge' of cocaine or saline on days 7 and 8. The DA and DA metabolite concentrations were measured using microdialysis on day 8. Ethanol enhanced the effect of cocaine on DA concentration in the NAcc as compared to a single administration of cocaine. The DA levels increased and reached their maximum values within 20-40 min after the cocaine administration, then gradually declined until the next injection 1-h later. Cocaine-induced stereotypic behavior was significantly increased in both saline and ethanol pretreated groups, though there was no significant difference between the two groups. The results of this study suggest that the enhanced DA transmission may be related to the experience produced by concurrent abuse of ethanol and cocaine in humans.

Cocaine and alcohol interactions in the rat: effect of cocaine and alcohol pretreatments on cocaine pharmacokinetics and pharmacodynamics

This experiment was designed to investigate the effect of pretreatment with cocaine and alcohol on cocaine pharmacokinetics and pharmacodynamics. Four groups of rats (n = 8 per group) received one of the following pretreatments for two weeks: none, alcohol (10% v/v in drinking water), cocaine (15 mg/kg/day ip), and alcohol+cocaine (10% v/v in drinking water + 15 mg/kg/day ip). On the day of the experiment, cocaine was administered (30 mg/kg, ip) to each rat, either alone or in combination with alcohol (5 g/kg, po), in a balanced crossover experimental design. Plasma and brain ECF concentrations of cocaine and its three metabolites: benzoylecgonine, norcocaine, and cocaethylene were assayed by HPLC-UV. The percent change in brain dopamine concentration, mean arterial blood pressure, and heart rate were determined simultaneously. A sigmoid-E(max) model was used to describe the brain cocaine concentration-neurochemical effect (dopamine) relationship, and an indirect pharmacodynamic response model was used to describe the plasma cocaine concentration-cardiovascular effect relationships. Alcohol pretreatment led to significant increase in cocaine AUC(p), alpha(t1/2), and beta(t1/2). Cocaine pretreatment significantly increased cocaine bioavailability, absorption rate constant, TBC, and the formation clearance of cocaethylene. Acute alcohol coadministration with cocaine increased cocaine AUC(p) and bioavailability, reduced the fraction of cocaine dose converted to benzoylecgonine, and increased the formation of norcocaine. These results indicate that the pharmacokinetics of cocaine, either administered alone or in combination with alcohol, is significantly altered due to prior cocaine and/or alcohol use. Both cocaine and alcohol pretreatments increased the E(max) for dopamine, with no effect on the EC(50). Acute alcohol coadministration with cocaine significantly increased the E(max) for dopamine and reduced the EC(50). Cocaine pretreatment significantly decreased the I(max) for blood pressure, IC(50), and R(max). For the heart rate response, both alcohol and cocaine pretreatments significantly increased the IC(50), with no effect on I(max). These results indicate that both cocaine and alcohol pretreatments as well as acute alcohol coadministration lead to significant alterations in cocaine pharmacodynamics that are due, at least in part, to the changes in cocaine pharmacokinetics. If similar effects occur in humans, chronic cocaine and alcohol abusers may respond differently to cocaine administration compared to naïve users and may be at higher risks of cocaine central nervous system toxicity.

Cocaine and alcohol interactions in the rat: contribution of cocaine metabolites to the pharmacological effects

The pharmacokinetics and pharmacodynamics of cocaine and its three metabolites, benzoylecgonine, norcocaine, and cocaethylene, were investigated in awake, freely moving rats. This work was performed to examine the effect of alcohol coadministration on the metabolic profile of cocaine and to determine the contribution of cocaine metabolites to the pharmacological responses observed after cocaine administration. The plasma and brain extracellular fluid concentration-time profiles were characterized after intravenous (iv) administration of cocaine and the three metabolites in a crossover experimental design. The neurochemical response, measured as the change in dopamine concentration in the nucleus accumbens, and the cardiovascular responses, measured as the change in the mean arterial blood pressure, heart rate, and QRS interval, were monitored simultaneously. Cocaethylene had the highest brain-to-plasma distribution ratio, followed by cocaine, norcocaine, and benzoylecgonine. The estimated total body clearances for cocaine, benzoylecgonine, norcocaine, and cocaethylene were 140 +/- 19, 14.7 +/- 1.2, 130 +/- 19, and 111 +/- 16 mL/min/kg, respectively. Alcohol coadministration increased the formation of norcocaine, decreased the formation of benzoylecgonine, and resulted in the formation of the pharmacologically active metabolite cocaethylene. When cocaine was administered with alcohol, 12.9 +/- 3.1% to 15.3 +/- 2.9% of the cocaine dose was converted to cocaethylene. Benzoylecgonine did not have any central nervous system or cardiovascular activities after iv administration. Compared with cocaine, norcocaine and cocaethylene had more potent and prolonged effects on the neurochemical, heart rate, and QRS interval responses, and were equipotent in increasing the mean arterial blood pressure. These results indicate that changes in the cocaine metabolic profile and the formation of the pharmacologically active metabolite cocaethylene are, at least partially, responsible for the more intense and longer lasting effects reported after using this drug in combination with alcohol.