Control Drug Intake Research Articles

Alterations of prefrontal cortical microRNAs in methamphetamine self-administering rats: From controlled drug intake to escalated drug intake

Drug addiction is a process that transits from recreative and regular drug use into compulsive drug use. The two patterns of drug use, controlled drug intake and escalated drug intake, represent different stages in the development of drug addiction; and escalation of drug use is a hallmark of addiction. Accumulating studies indicate that microRNAs (miRNAs) play key regulatory roles in drug addiction. However, the molecular adaptations in escalation of drug use, as well as the difference in the adaptations between escalated and controlled drug use, remain unclear. In the present study, 28 altered miRNAs in the prefrontal cortex (PFC) were found in the groups of controlled methamphetamine self-administration (1h/session) and escalated self-administration (6h/session), and some of them were validated. Compared with saline control group, miR-186 was verified to be up-regulated while miR-195 and miR-329 were down-regulated in the rats with controlled methamphetamine use. In the rats with escalated drug use, miR-127, miR-186, miR-222 and miR-24 were verified to be up-regulated while miR-329 was down-regulated compared with controls. Furthermore, bioinformatic analysis indicated that the predicted targets of these verified miRNAs involved in the processes of neuronal apoptosis and synaptic plasticity. However, the putative regulated molecules may be different between controlled and escalated drug use groups. Taken together, we detected the altered miRNAs in rat PFC under the conditions of controlled methamphetamine use and escalated use respectively, which may extend our understanding of the molecular adaptations underlying the transition from controlled drug use to addiction.

New direct and indirect methods for the detection of cyclooxygenase 1 acetylation by aspirin; the lack of aspirin resistance among healthy individuals

BackgroundAspirin is widely used in the prevention of acute atherothrombotic complications. It acetylates Ser529 residue in cyclooxygenase-1 (COX-1) and prevents thromboxane A2 (TXA2) formation from arachidonic acid (AA) in platelets. Laboratory methods used for the detection of aspirin effect provide inconsistent results. MethodsTwo new methods were developed for the direct and indirect detection of COX-1 acetylation by aspirin in 108 healthy volunteers treated daily with 100mg enteric-coated aspirin for 7days. Monoclonal antibodies were raised against acetylated and non-acetylated nonapeptides corresponding to the amino acid sequence of human COX-1 525–533 residues. Using Western blotting technique the antibodies clearly distinguished between acetylated and non-acetylated COX-1 in platelet lysate. The second method measures AA-induced TXB2 production of platelets in diluted platelet rich plasma. ResultsNo acetylated COX-1 was detected in platelets before aspirin treatment. At the same time antibodies raised against non-acetylated peptide gave intense reaction with COX-1 on the Western blot. In contrast, after 7days of aspirin treatment, with a single exception, only acetylated COX-1 could be detected in the platelet lysate. The non-responding volunteer showed full response to aspirin after controlled drug intake. In parallel experiments aspirin treatment for 7days practically completely inhibited AA-induced TXB2 production by platelets. ConclusionsChemical (“true”) aspirin resistance, if it exists, must be a rarity among healthy individuals. The new methods could be used for detecting the acetylation of COX-1 by aspirin in patients on preventive aspirin therapy and for evaluating methods routinely used for such purpose.

The Role of Dentate Gyrus Neurogenesis in Neuropsychiatric Disorders

The Role of Dentate Gyrus Neurogenesis in Neuropsychiatric Disorders

Molecular, Cellular, and Structural Mechanisms of Cocaine Addiction: A Key Role for MicroRNAs

The rewarding properties of cocaine play a key role in establishing and maintaining the drug-taking habit. However, as exposure to cocaine increases, drug use can transition from controlled to compulsive. Importantly, very little is known about the neurobiological mechanisms that control this switch in drug use that defines addiction. MicroRNAs (miRNAs) are small non-protein coding RNA transcripts that can regulate the expression of messenger RNAs that code for proteins. Because of their highly pleiotropic nature, each miRNA has the potential to regulate hundreds or even thousands of protein-coding RNA transcripts. This property of miRNAs has generated considerable interest in their potential involvement in complex psychiatric disorders such as addiction, as each miRNA could potentially influence the many different molecular and cellular adaptations that arise in response to drug use that are hypothesized to drive the emergence of addiction. Here, we review recent evidence supporting a key role for miRNAs in the ventral striatum in regulating the rewarding and reinforcing properties of cocaine in animals with limited exposure to the drug. Moreover, we discuss evidence suggesting that miRNAs in the dorsal striatum control the escalation of drug intake in rats with extended cocaine access. These findings highlight the central role for miRNAs in drug-induced neuroplasticity in brain reward systems that drive the emergence of compulsive-like drug use in animals, and suggest that a better understanding of how miRNAs control drug intake will provide new insights into the neurobiology of drug addiction.

Modulators of Very Low Voriconazole Concentrations in Routine Therapeutic Drug Monitoring

Very low voriconazole concentrations are commonly observed during therapeutic drug monitoring. Possible mechanisms include inappropriate dose selection, rapid metabolism (as a result of genetic polymorphisms or enzyme induction), and also nonadherence. We aimed to develop a method to distinguish between rapid metabolism of and nonadherence to voriconazole by quantification of voriconazole metabolites. In addition, the relevance of common genetic polymorphisms of CYP2C19 was assessed. In a retrospective study, samples with voriconazole concentrations 0.2 μg/mL or less in routine therapeutic drug monitoring (as quantified by high-performance liquid chromatography) were evaluated. Voriconazole and its N-oxide metabolite were quantified in residual blood using a highly sensitive liquid chromatography-tandem mass spectroscopy method (lower limit of quantitation = 0.03 μg/mL). Genetic polymorphisms of CYP2C19 were determined by real-time polymerase chain reaction using the hybridization probe format and the polymerase chain reaction-random fragment length polymorphism format. A total of 747 routine therapeutic drug monitoring plasma/blood samples of 335 patients treated with systemic voriconazole were analyzed and in 18.7% of all samples, voriconazole concentrations 0.2 μg/mL or less were found. In 32 samples (30 patients) with adequate dosage and timing of blood withdrawal, nonadherence was strongly suspected in seven patients because voriconazole-N-oxide concentrations were below 0.03 μg/mL, which was not observed in a reference group of 51 healthy volunteers with controlled drug intake. In 10 patients, of whom EDTA blood was available, the ultrarapid metabolizer genotype (CYP2C19*1\*17, CYP2C19*17\*17) was found in 80% and its prevalence was significantly higher as compared to a reference group (P = 0.02). In conclusion, quantification of voriconazole-N-oxide allowed for detection of suspected nonadherence in one of four patients with very low voriconazole concentrations. In the remaining patients, ultrarapid metabolism resulting from the CYP2C19*17 polymorphism appears to play a major role. Thus, in the case of voriconazole therapy failure, both nonadherence and genetic factors have to be considered.

Transition to Addiction Is Associated with a Persistent Impairment in Synaptic Plasticity

Chronic exposure to drugs of abuse induces countless modifications in brain physiology. However, the neurobiological adaptations specifically associated with the transition to addiction are unknown. Cocaine self-administration rapidly suppresses long-term depression (LTD), an important form of synaptic plasticity in the nucleus accumbens. Using a rat model of addiction, we found that animals that progressively develop the behavioral hallmarks of addiction have permanently impaired LTD, whereas LTD is progressively recovered in nonaddicted rats maintaining a controlled drug intake. By making drug seeking consistently resistant to modulation by environmental contingencies and consequently more and more inflexible, a persistently impaired LTD could mediate the transition to addiction.

Cocaine self-administration in rats with histories of cocaine exposure and discrimination

Interrelationships between the discriminative stimulus and reinforcing properties of psychoactive drugs and the way in which they may interact to control drug intake are unclear. Studies have shown that drug history can influence the expression of drug-produced behavioral effects. The present study examined the acquisition and maintenance of intravenous cocaine self-administration in rats with a history of drug discrimination. Two groups of male hooded rats (n=12 each) were successfully trained in a single-lever food-reinforced procedure to discriminate cocaine (10 mg/kg) from saline. Control groups (n=12 each) received drug injections and/or saline injections only and lever-pressed for food reinforcers with no discrimination training. Subsequently, all subjects were implanted with chronic jugular catheters and allowed to nose-poke for infusions of cocaine (0.2 mg/kg per infusion). Initial rates of responding were similar for all groups. Acquisition of self-administration on a FR-10 schedule of drug delivery was significantly faster for cocaine-exposed rats in comparison to all other groups (P<0.02). There were no differences between groups in the breaking points of cocaine and saline on a progressive ratio schedule of self-administration. Dose-response functions were obtained by two methods and were similar for all groups. These results are consistent with earlier studies demonstrating weakly sensitized primary reinforcing properties of cocaine in preexposed rats. Previous learning to discriminate cocaine impaired this sensitization.

Addiction and its brain science

To illustrate how modern neurobiological approaches will help to identify the neurocircuits and genes involved in addictive behavior. The current disorder concept of addiction includes neurobiological foundations and neurobiological research assuming irreversible molecular and structural changes within the brain dopamine reinforcement system, constituting the 'molecular and structural switch' from controlled drug intake to compulsive drug abuse. However, those irreversible changes have not so far been identified and it is suggested that in addition to the mesolimbic dopamine system, other brain systems including the mesocortical and nigrostriatal pathways as well as their non-dopaminergic feedback-loops might be involved in addictive behavior. NEUROBIOLOGICAL APPROACH: A three-step neurobiological approach is described that allows in a first step via novel animal models and imaging techniques to identify the neuroanatomical sites mediating voluntary drug intake, reinstatement of drug-seeking behavior, relapse, loss of control and drug intake despite negative consequences. In a subsequent step, forward genetic approaches including quantitative trait loci (QTL)-analysis and gene expression profiling are helpful in identifying so-called candidate genes. In a final step, conditional animal mutants and selective pharmacological tools are used to functionally validate candidate genes. Following this validation process, the transfer to the human situation has to be made and candidate genes have to be verified further in well-phenotyped cohorts of addicted patients. This three-step neurobiological approach, that must involve an interdisciplinary team including experimental psychologists, geneticists, molecular biologists and finally clinical addiction researchers, will allow us to understand where and how the addicted brain goes awry.

Access conditions are crucial: comment on Lynch and Carroll (2001).

W. J. Lynch and M. E. Carroll (2001) sought to identify factors that control drug intake, that is, factors that decrease the avidity of drug seeking and drug taking while drug is obviously available. The review provides updated information about factors that regulate drug intake and a heuristic framework for future studies of regulatory processes throughout the natural history of a substance abuse disorder. In particular, the review suggests a productive framework for studies of transitions from early drug use to later abusive use. Forceful identification of factors that control the avidity of drug seeking and drug taking under the controlled conditions of the laboratory may encourage development of therapeutic interventions that capitalize on these factors for successful treatment of human drug abuse. Extending the analysis of regulation of intake to include factors that can be manipulated to reorganize behavior may improve the design of interventions to treat drug abuse.

From controlled drug intake to loss of control: the irreversible development of drug addiction in the rat

The development of drug taking from controlled intake to drug addiction was studied by means of an animal model. Outbred rats had continous free access to water and drinking fluids containing different concentrations of a drug for 7–9 months. After an abstinence period of 4–9 months, the drug was offered again (retest). Previous ethological classification of each rat and changes of housing conditions were used to study the modifiability of drug taking. With ethanol and the μ-agonistic opiate etonitazene, two stages followed each other. Controlled drug intake was adjusted to situational and individual variables. Social isolation of the rats raised the intake of ethanol and opiate. Dominant rats took less drugs than subordinate ones, but, in contrast to the latter, increased drug consumption after social disturbances. The adjustment of drug taking to social variables, was accompanied by changes in the dopaminergic and GABA A-ergic neurotransmission and by altered responses to acute drug administrations. Further, place preference, associated with reinforcing stimuli was modulated by subchronic sensitization/desensitization of dopaminergic transmission. Controlled drug intake lasted for 6–8 months, after which a spontaneous increase of drug consumption was found which latently continued during abstinence periods of 1 month. In the retest after abstinence, drug intake of these rats was strongly increased compared with both their previous consumption and that of drug-naive controls. Since drug taking could no longer be modulated by gustatory, environmental or individual factors (loss of control), it was considered as addictive. Addiction appeared to be specific to the kind of the drug. It persisted for the rest of the rat's life. After long periods of abstinence, ethanol-addicted rats revealed a completely altered pattern of response to self-administered alcohol compared with controlled drinkers. Their dopaminergic D 1-transmission was irreversibly altered. Drug addiction only developed when the rat had free choice between water and drug-containing solutions. Long-term forced administration of ethanol or opiate, only led to physical dependence bot not to addiction. Some applications of the animal model are discussed, concerning the assessment of risk factors, the intake of drug combinations, residual neurochemical changes and concepts of treatment.