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PubMed2004

Glucocorticoids and vulnerability to psychostimulant drugs: toward substrate and mechanism.

Glucocorticoid hormones can modulate the propensity of individuals to develop addictive behavior and, by doing so, contribute to the existence of individual differences in vulnerability to drugs. This article summarizes recent findings that increase our knowledge about drug-induced neuronal adaptations in the brain reward system and the role glucocorticoids may play in this process. Evidence exists that drugs and stress can induce similar changes in excitatory synaptic strength within the mesolimbic dopamine system, suggesting a coordinate mechanism for drugs of abuse and glucocorticoids. The glucocorticoid receptor (GR) plays an essential role in the stress-induced synaptic alterations, and studies using transgenic mice suggest that the GR is a key modulator of the motivation to take drugs and of the behavioral effects of repeated drug intake. The current state of research into the interplay between glucocorticoid hormones and addiction has reached a new phase in which detailed cellular and molecular analyses of the actual mechanisms will become possible. An important role is assigned to the GR, although many issues remain to be addressed, such as the actual site of glucocorticoid action in the brain, the molecular mechanisms and targets of GR-mediated glucocorticoid effects, and their interaction with genetic background.

Animals↗

PubMed2025

Multi-Locus Pro-Dopaminergic Restoration of Reward Brain Circuitry in Reward Deficiency Rescinds Mono-Pharmaceutical Targeting.

Dopaminergic dysfunction in reward circuitry is well-documented as a contributor to addictive behaviors. Evidence indicates that changes in synchronous neural activity between brain regions mediating reward and cognitive functions may significantly contribute to substance-related disorders. In this commentary we highlight findings showing that the pro-dopaminergic nutraceutical (KB220) enhances functional connectivity between reward and cognitive brain areas in both animal and human studies. Animal studies demonstrate that KB220 activates important brain reward-related regions, including the nucleus accumbens, anterior cingulate gyrus, anterior thalamic nuclei, hippocampus, and prelimbic and infralimbic loci. Kb220 induced significant functional connectivity, enhanced neuroplasticity, and improved dopaminergic functionality within the brain reward circuitry with effects localized to these regions rather than broader distributed across the brain. In abstinent heroin-dependent individuals, acute KB220 administration significantly induced BOLD activation in caudate-accumbens dopaminergic pathways relative to placebo. Furthermore, data from 36 clinical trials and preclinical studies encompassing over 1,000 subjects, demonstrate that KB220 supports "dopamine homeostasis" across various reward deficiency behaviors. Clinical outcomes and quantitative electroencephalogy (qEEG) results underscore KB220's potential anti-craving/anti-relapse effects in addiction and other psychiatric disorders through direct or indirect dopaminergic modulation. Based on a review of the existing knowledge and further intensive investigation, we propose that instead of relying on mono-pharmaceutical approaches, the scientific community should endorse multi-loci dopaminergic restoration of reward brain circuitry as a fundamental paradigm for addressing mental illness.

Alcohol Use Disorder (AUD)↗

PubMed2004

Partial deletion of the cAMP response element-binding protein gene promotes alcohol-drinking behaviors.

The cAMP response element-binding protein (CREB) gene transcription factor has been shown to play a role in the synaptic plasticity associated with drug addictive behaviors; however, the causal role of the CREB gene in alcohol-drinking behaviors is unknown. The present investigation evaluated alcohol-drinking behaviors in mice that are haplodeficient in CREB as a result of targeted CREB (alpha and Delta) gene disruption. It was found that CREB-haplodeficient (+/-) mice have higher preference for ethanol but not for sucrose solution than wild-type (+/+) littermates. The functional aspects of the CREB gene transcription factor were also investigated by measuring the protein levels of phosphorylated CREB (p-CREB) and the expression of cAMP-inducible genes such as neuropeptide Y (NPY) and brain-derived neurotrophic factor (BDNF). Deletion of the CREB (alpha and Delta) gene significantly decreases total CREB, p-CREB levels and the expression of NPY and BDNF in the brain structures of CREB-deficient (+/-) mice. It was also found that CREB-deficient (+/-) mice displayed more anxiety-like behaviors and that acute ethanol exposure produced anxiolytic effects and significantly increased protein levels of p-CREB and NPY in the central and medial but not in the basolateral amygdala of wild-type mice, but these effects are attenuated in CREB-deficient mice compared with wild-type mice. These results provide the first direct evidence that a haplodeficiency of the CREB gene is associated with increased alcohol-drinking behaviors. Furthermore, alcohol drinking and anxiety-like behaviors in CREB-haplodeficient mice may possibly be related to decreased expression of NPY and BDNF in the brains of these mice.

Alcohol Drinking↗

PubMed2001

Repeated intermittent administration of psychomotor stimulant drugs alters the acquisition of Pavlovian approach behavior in rats: differential effects of cocaine, d-amphetamine and 3,4- methylenedioxymethamphetamine ("Ecstasy").

BACKGROUND: Psychomotor stimulant drugs can produce long-lasting changes in neurochemistry and behavior after multiple doses. In particular, neuroadaptations within corticolimbic brain structures that mediate incentive learning and motivated behavior have been demonstrated after chronic exposure to cocaine, d-amphetamine, and 3,4-methylenedioxymethamphetamine (MDMA). As stimulus-reward learning is likely relevant to addictive behavior (i.e., augmented conditioned reward and stimulus control of behavior), we have investigated whether prior repeated administration of psychomotor stimulant drugs (of abuse, including cocaine, d-amphetamine, or MDMA, would affect the acquisition of Pavlovian approach behavior. METHODS: Water-deprived rats were tested for the acquisition of Pavlovian approach behavior after 5 days treatment with cocaine (15-20 mg/kg once or twice daily), d-amphetamine (2.5 mg/kg once or twice daily), or MDMA (2.5 mg/kg twice daily) followed by a 7-day, drug-free period. RESULTS: Prior repeated treatment with cocaine or d-amphetamine produced a significant enhancement of acquisition of Pavlovian approach behavior, indicating accelerated stimulus-reward learning, whereas MDMA administration produced increased inappropriate responding, indicating impulsivity. Abnormal drug-induced approach behavior was found to persist throughout the testing period. CONCLUSIONS: These studies demonstrate that psychomotor stimulant-induced sensitization can produce long-term alterations in stimulus-reward learning and impulse control that may contribute to the compulsive drug taking that typifies addiction.

Animals↗

PubMed2002

Second-order schedules of drug self-administration in animals.

On a second-order schedule, a subject responds according to one schedule (the unit schedule) for a brief presentation of a stimulus such as a light. Responding by the subject on this unit schedule is then reinforced according to another schedule of reinforcement. Second-order schedules of drug injection allow the study of more complex behavioral sequences than do simple schedules and may more accurately reflect the human drug-abuse situation. Much of the early work in this area used primates as subjects and focused on the behavioral variables controlling responding. It was shown that long sequences of behavior could be maintained on second-order schedules with relatively infrequent injections of drug and that the second-order, brief-stimulus presentations were critical to the acquisition and maintenance of responding. Also, the continued presentation of the brief stimulus in extinction often led to prolonged extinction behavior. These studies clearly showed that environmental stimuli greatly influence drug self-administration behavior under second-order schedules. The focus of much of the more recent work with second-order schedules has been on the evaluation of pharmacological treatments for drug addiction, both as antagonist and substitution therapies. Both types of potential therapies have shown promise in these preclinical models of addictive behavior. The recent extension of second-order self-administration studies to rats as subjects has facilitated the investigation of neural mechanisms involved in this behavior. While this use of second-order schedules is a relatively recent phenomenon, significant contributions have already been made in identifying neural mechanisms critical to second-order schedule drug self-administration. This active area of research holds great promise for delineating specific brain regions critical to different aspects of drug addiction.

Animals↗

PubMed2006

Behavioral and molecular effects of dopamine D1 receptor stimulation during naloxone-precipitated morphine withdrawal.

Morphine dependence is characterized by somatic and motivational signs of withdrawal that likely contribute to the maintenance of addictive behavior. The nucleus accumbens (NAc) receives extensive dopaminergic input and is an important substrate for mediating these aversive states. In the NAc, the function of the transcription factor cAMP response element binding protein (CREB) and AMPA glutamate receptor subunit, type 1 (GluR1) can be regulated by dopamine (DA) D1 receptor-mediated phosphorylation (P-CREB, P-GluR1). However, the roles of D1 receptors, CREB, and GluR1 in morphine dependence are not well understood. Here, we show that somatic signs of naloxone-precipitated withdrawal were associated with increased P-CREB, but not P-GluR1, in the NAc of morphine-dependent rats. The D1 receptor agonist chloro-APB hydrobromide (SKF 82958) was rewarding in morphine-dependent rats and blocked naloxone-induced place aversions and somatic signs of withdrawal. Surprisingly, SKF 82958 increased P-GluR1, but not P-CREB, in the NAc, and naloxone reduced SKF 82958-mediated P-GluR1 induction specifically in morphine-dependent rats. Together, these results confirm that aversive treatments can increase CREB function in the NAc. Furthermore, they suggest a dependence-associated shift in the molecular mechanisms that regulate the consequences of D1 receptor stimulation, favoring activation of GluR1 rather than CREB. These data raise the possibility that the rewarding effects of SKF 82958 in morphine-dependent rats involve increased P-GluR1 in the NAc, although the involvement of other brain regions cannot be ruled out. Regardless, these findings suggest for the first time that D1 agonists might be useful for the treatment of withdrawal symptoms that contribute to the maintenance of opiate addiction in humans.

Animals↗

PubMed1990

Addiction, helplessness, and narcissistic rage.

In many cases addictive behavior serves to ward off a sense of helplessness or powerlessness via controlling and regulating one's affective state. Addicts have a vulnerability to feelings of powerlessness, which reflects a specific narcissistic impairment. The drive in addiction to re-establish a sense of power is, correspondingly, impelled by narcissistic rage. This rage gives to addiction some of its distinctive clinical properties. The narcissistic vulnerability in addicts is discussed. Several brief clinical cases are provided, and the view proposed is correlated with other psychoanalytic perspectives.

Adult↗

PubMed1998

Is craving the source of compulsive drug use?

Compulsive drug use, which is typically portrayed as a defining quality of addictive behavior, has been described as a pattern of drug consumption that is stimulus bound, stereotyped, difficult to regulate and identified by a loss of control over intake. It is widely assumed that compulsive drug use is caused by drug craving. This assumption is supported by numerous findings of a general correspondence between measures of craving and drug-use behavior. A more focussed analysis of the available data, however, reveals that craving and drug use are not coupled to the degree required by the hypothesis that craving is the source of all drug use in the addict. As an alternative to this craving-based view, compulsive drug use could be characterized as a form of automatized behavior. Automatic performance is assumed to develop over the course of repeated practice of motor and cognitive skills. Automatized behavior, like compulsive drug use, tends to be stimulus bound, stereotyped, effortless, difficult to control and regulated largely outside of awareness. The formulation of drug compulsion as a manifestation of automaticity rather than craving allows addiction researchers to apply methods and measures derived from cognitive sciences to investigate the fundamental organization of compulsive drug-use behavior.

Cognition↗

PubMed2001

Cocaine-predictive stimulus induces drug-seeking behavior and neural activation in limbic brain regions after multiple months of abstinence: reversal by D(1) antagonists.

The conditioning of cocaine's subjective actions with environmental stimuli may be a critical factor in long-lasting relapse risk associated with cocaine addiction. To study the significance of learning factors in persistent addictive behavior as well as the neurobiological basis of this phenomenon, rats were trained to associate discriminative stimuli (S(D)) with the availability of i.v. cocaine vs. nonrewarding saline solution, and then placed on extinction conditions during which the i.v. solutions and S(D)s were withheld. The effects of reexposure to the S(D) on the recovery of responding at the previously cocaine-paired lever and on Fos protein expression then were determined in two groups. One group was tested immediately after extinction, whereas rats in the second group were confined to their home cages for an additional 4 months before testing. In both groups, the cocaine S(D), but not the non-reward S(D), elicited strong recovery of responding and increased Fos immunoreactivity in the basolateral amygdala and medial prefrontal cortex (areas Cg1/Cg3). The response reinstatement and Fos expression induced by the cocaine S(D) were both reversed by selective dopamine D(1) receptor antagonists. The undiminished efficacy of the cocaine S(D) to elicit drug-seeking behavior after 4 months of abstinence parallels the long-lasting nature of conditioned cue reactivity and cue-induced cocaine craving in humans, and confirms a significant role of learning factors in the long-lasting addictive potential of cocaine. Moreover, the results implicate D(1)-dependent neural mechanisms within the medial prefrontal cortex and basolateral amygdala as substrates for cocaine-seeking behavior elicited by cocaine-predictive environmental stimuli.

Animals↗

PubMed2004

Familial hypothalamic digoxin deficiency syndrome.

The case report of a family with coexistence of hypotension, recurrent respiratory infection, motor tics, obsessive-compulsive disorder (OCD), major depressive disorder, early onset osteoporosis, low body mass index, bulimia nervosa, and healthy aging with longevity is described. The family members had hyposexual behavior and less tendency toward spirituality. They did not have insomnia, but they did display tendency toward increased somnolence. No addictive behavior was observed. The family demonstrated a high level of bonding and affectionate behavior, and they were less creative, with an average intelligence quotient (IQ). There was a total absence of vascular thrombosis, systemic neoplasms and neuronal degeneration in the indexed family. All members of the indexed family were left hemispheric dominant. The levels of serum digoxin, HMG-CoA reductase activity, and dolichol were found to be decreased in the members of the indexed family, with a corresponding increase in red blood cell (RBC) Na(+)-K+ ATPase activity, serum ubiquinone and magnesium levels. There was increase in tyrosine catabolites and a reduction in tryptophan catabolites in the serum. The total and individual glycosaminoglycan fractions, carbohydrate residues of glycoproteins, activity of glycosaminoglycans (GAG) degrading enzymes, and glycohydrolases were decreased in the serum. The concentration of RBC membrane total GAG and carbohydrate residues of glycoproteins increased, while the cholesterol: phospholipid ratio of the membrane decreased. The activity of free radical scavenging enzymes were increased, while the concentration of free radicals decreased significantly. The same biochemical patterns were observed in left hemispheric dominance as opposed to right hemispheric dominance. The significance of these findings in the pathogenesis of these disorders is discussed.

Body Mass Index↗

PubMed1999

[Drug-induced headache--pathomechanisms of addiction].

The pathogenesis of drug abuse in patients suffering from drug-induced headache is not known in detail. It is unclear whether drug abuse in chronic daily headache should be classified as a form of drug dependence. Current findings concerning the neurobiological correlates of addictive behavior and affective disorders point to the importance of monoaminergic dysregulation, especially a dysfunction of central serotonergic neurotransmission. We reviewed the literature on drug-induced headache and examined hypothetical pathomechanisms of addiction. Drugs causing drug-induced headache such as paracetamol, coffein and ergotamine interfere with behavior patterns or neurotransmitter systems that are also affected by drugs of abuse. Several drugs that ameliorate acute headache interact with central serotonergic neurotransmission and may affect anxiety and depression in patients with chronic daily headache. Non human primate and human studies revealed mechanisms of serotonergic dysfunction in drug dependence, which may also be relevant for drug-abuse in medication-induced headache. Medication-induced dysfunction of monoaminergic, especially serotonergic neurotransmission, may affect drug dependence by exacerbating mood disorders. Further studies are necessary to assess serotonergic neurotransmission in patients with drug-induced headache and abuse of medication.

English Abstract↗

PubMed2003

Altered cocaine-induced behavioral sensitization in adult mice exposed to cocaine in utero.

Behavioral sensitization induced by psychostimulants is characterized by increased locomotion and stereotypy and may reflect aspects of neuronal adaptations underlying drug addiction in humans. To study the developmental contributions to addictive behaviors, we measured behavioral responses in adult offspring to a cocaine sensitization paradigm following prenatal cocaine exposure. Pregnant Swiss-Webster (SW) mice were injected twice daily from embryonic days 8 to 17 (E8-E17, inclusive) with cocaine (20 or 40 mg/kg/day; COC20 and COC40, respectively), or saline vehicle (SAL and SPF40) subcutaneously (s.c.). A nutritional control group of dams were 'pair-fed' with COC40 dams (SPF40). P120 male offspring from each prenatal treatment group were assigned to a behavioral sensitization group and injected with cocaine (15 mg/kg) or saline intraperitoneally (i.p.) every other day for seven doses. Locomotor activity and stereotypy were measured during habituation, cocaine initiation, and following a cocaine challenge 21 days after the last initiation injection. As expected, animals demonstrated significantly more locomotion and stereotypic behavior following acute and recurrent injection of cocaine compared to saline-injected animals. However, for each prenatal treatment group, cocaine-sensitized animals showed unique temporal profiles for the increase in locomotor sensitization and stereotypy over the course of the sensitization protocol. Two features that distinguished the altered behavioral progression of prenatally cocaine-exposed animals (COC40) from control (SAL) animals included blunted augmentation of locomotion and enhanced patterns of stereotypic behavior. These findings provide evidence that the behavioral activating effects of cocaine in adult animals are altered following exposure to cocaine in utero.

Animals↗

PubMed2002

Health behaviors and health status of older women with schizophrenia.

The authors interviewed 43 women with schizophrenia who were 40 to 70 years of age about their health status, preventive health care, addictive behaviors, and comorbid medical conditions. Data were compared with those for age-matched samples from the general population. Thirty women in the study sample (71 percent) were overweight or obese, compared with 38 percent in the general population. Twenty-seven (63 percent) smoked cigarettes. Twenty-six women (62 percent) had received a mammogram in the past two years, compared with 86 percent in the general population. Rates of routine physical examinations and Pap tests did not differ markedly between the study sample and the general population. These results highlight the health impairments of older women who have schizophrenia.

Adult↗

PubMed2001

The neurobiology of pathological gambling.

Despite relatively high prevalence rates and significant morbidity and mortality associated with pathological gambling (PG), our understanding of the neurobiological basis of PG lags in comparison to that for other psychiatric illnesses of comparable magnitude. An improved understanding of the neurobiology of PG would facilitate targeted investigations into more effective treatments. Emerging data suggest shared neurobiological features determine in part pathological gambling and substance use disorders. These findings both challenge current conceptualizations of addictions and provide a substantial basis of knowledge on which to design investigations into the understanding and treatment of pathological gambling. The findings that substance use disorders and the behavioral "addiction" of PG share common causative features raise the question as to what extent other compulsive disorders (eg, compulsive shopping, compulsive sexual behaviors, compulsive computer use) might be biologically related.

Animals↗

PubMedDate not supplied

Policy and medical-legal issues in the prescribing of controlled substances.

The physician who prescribes controlled substances is faced with an array of laws, regulatory policies, and professional attitudes about their use. Prescriptions for these scheduled drugs are furthermore monitored by the pharmacists who dispense them. Certain drugs, such as the opioids and the benzodiazepines, are considered so potentially abusive that special programs have been recommended to track the behavior of physician prescribers. Multiple copy programs have been implemented in some states. More recent proposals recommend electronic data transfer (EDT) of pharmacy information to centralized processing points so that misprescribing physicians and doctor-shopping patients can be identified. Regulators concerned about physician behavior and confronted by demands of nonphysicians to prescribe controlled substances may find EDT a good solution. Physicians should be concerned about being censured for misprescribing, because such actions may lead to inclusion in the National Practitioner Data Bank. With all of the regulatory concerns about controlled substances, those physicians who would employ long-term opioid therapy for their chronic pain patients must follow certain basic guidelines to be able to defend themselves against allegations of deviant professional behavior. Such procedures as conducting a history and physical examination, maintaining a written treatment plan, consulting with knowledgeable colleagues, and assessing for addictive behavior can provide the practitioner with safeguards.

Drug Prescriptions↗

PubMedDate not supplied

[Analgesic abuse and psychiatric comorbidity in headache patients].

Headache patients frequently overuse analgesic medications: 20% of the patients from headache centers is concerned by this problem, which has been estimated to occur in four percent of the community migrainers. Frequent use of various types of headache medication may paradoxically cause an increase in headache attack frequency as well as their chronicisation due to potentially complex mechanisms of sensitization. Patients will enter into a self- perpetuating cycle of daily headaches and use of symptomatic medications which can lead to addiction and to social and occupational impairement. Indeed, many patients will experience pharmacological tolerance and dependence but also by some kind of craving. International Headache Society qualify these patients as abusers referring mostly to the amount of substance ingested. Hence patients are labelled analgesic abusers . However, as many of these analgesic medications contained psychotropic substances (i.e. caffeine, codeine.), these patients may fulfill DSM IV criteria of dependance. Nevertheless, the dependance criteria should be adapted to chronic pain patients. Indeed, if pharmacological dependence and tolerance criteria are easy to apply in such patients, it is not the case for the criteria a great deal of time spent to obtain substances, to use substances or to recover from substances effects . As analgesic medications are legally obtained from medical practitioners, drug seeking behaviours are mostly: obtaining medications from multiple providers, repeating episodes of prescription loss and multiplying requests for early refills. Moreover the detrimental effects of analgesic abuse on psychosocial functioning is likely to be related to pain rather than to medication overuse. Finally the best indicator of addictive behaviors in such patients, is the loss of control over the use of analgesic medication despite the adverse consequences over pain. Comorbidity with addiction to other substances has never been specifically scrutinized in this population, but it is well documented that chronic pain patients have high rates of addiction with various types of substances. Moreover, it is well documented that these patients are at higher risk for anxious (panic disorders and phobic disorders) and depressive disorders than non abusing headache patients. Anxiety and depressive scores are related to both the chronicity of headaches, and the amount of analgesic intake. Therefore, this comorbidity is possibly related to psychoactive substance use but there is no prospective study concerning chronological link between the anxious and depressive disorders and analgesic abuse. The presence of personality disorders in these patients is poorly documented, with the exception of neuroticism, which probably reflects the anxious and depressive comorbidity. Clinical findings show that a subgroup of patients needs an hospitalisation to succeed in withdrawal. They appears likely to be dependant on several types of drugs, to present with fear of pain itself, and to present with cluster B personality disorders, whereas another subgroup is specifically dependant on one type of drug, present with fear of pain induced impairement, and present with cluster C personality disorders. Those patients, when becoming aware of dependance, succeed in withdrawal at home, without the need of an hospitalization. The analgesic medication overuse and dependance can also be considered as a maladjusted strategy to manage pain (with prevalent passive and avoidant coping strategies). More research is required focusing on psychopathological aspects of analgesic overuse and dependance, to improve withdrawal modalities and to reduce the rate of relapses.

Analgesics↗

PubMed2004

Behavioral and neurochemical vulnerability during adolescence in mice: studies with nicotine.

People are very likely to start psychoactive drug use during adolescence, an earlier onset being associated with a higher risk of developing addiction later in life. In experiment I, Pre- (postnatal day (pnd) 23-35), Mid- (pnd 36-48), or Post- (pnd 49-61) adolescent mice underwent a restricted-drinking period (2 h/day for 12 days), one bottle containing water and the other containing nicotine (10 mg/l) or water. After this period, Mid-adolescents showed prominent exploration and reduced anxiety in the plus-maze. This ontogenetic profile was dampened by nicotine consumption. After 2 months, these mice were tested in a novel environment (30 min/day for 3 days). Locomotor-habituation profiles were specifically disrupted by nicotine consumption during Mid-adolescence, suggesting this age as a critical period. In experiment II, Mid-adolescent (pnd 35-44) and adult (pnd > 70) mice were pretreated with nicotine (0, 0.03, 0.10, 0.30 mg/kg/day for 10 days). Acute nicotine administration had opposite effects on anxiety in adolescents and adults. At 2 months after pretreatment, we measured levels of AMPA GluR2/3 subunits, thought to be involved in the control of addictive behaviors. Nicotine exposure during Mid-adolescence dose-dependently downregulated these subunits in the striatum and hippocampus, but comparable exposure during adulthood had either opposite or no effects. NMDA NR2A/B subunits were affected by nicotine, but without age-related differences. The present data identified a nicotine-vulnerable age window, characterized by long-term disruption of locomotor habituation and downregulation of AMPA receptors. These findings support neurobiological vulnerability to drugs in adolescent humans.

Aging↗

PubMed1992

Oxidation chemistry and biochemistry of the central mammalian alkaloid 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline.

The electrochemical oxidation of the central mammalian alkaloid 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline (1) has been studied in neutral aqueous solution at a pyrolytic graphite electrode (PGE). Voltammograms of 1 show two closely spaced oxidation peaks, Ia and IIa. At potentials less positive than the peak potential (Ep) for peak Ia, 1 is oxidized to a radical intermediate which dimerizes to give two diastereomers of 5,5'-bi(1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline) (5 and 6). At potentials more positive than Ep for peak Ia the putative radical intermediate is further electrooxidized to a C(5)-centered carbocation which reacts with 1 in an ion-substrate reaction to give 5 and 6 or with water to give, ultimately, 1-methyl-1,2,3,4-tetrahydro-beta-carboline-5,6-dione (12). Dimers 5 and 6 give two reversible oxidation peaks at the PGE, the second of which corresponds to peak IIa observed in voltammograms of 1. Because 5 and 6 are easily oxidizable compounds they are only observed as products in the initial stages of the controlled potential electrooxidation of 1. Tyrosinase/O2, human ceruloplasmin/O2, and peroxidase/H2O2 also oxidize 1 to 5, 6, and 12 as the initial products. In the presence of glutathione the electrochemically driven and enzyme-mediated oxidations of 1 result in the formation of 5-S-glutathionyl-1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline as a major product. Central administration of diastereomer 5 or 6 to mice evoked behavioral responses similar to those caused by the opioid analgesics. These behavioral effects, which include spatial disorientation and a characteristic ducklike walk, became most pronounced approximately 3 h after drug administration and continued for about 3 days. Neurotransmitter and related metabolite analyses of whole brain reveal that 5 and 6 cause a general increase in dopaminergic and serotonergic activity and a small but significant decrease in cholinergic activity. These transmitter/metabolite disturbances appear to parallel the time course of the observed behavioral effects. The possible roles of in vivo oxidations of 1, an alkaloid which is elevated in mammalian brain following ethanol consumption, in the addictive, behavioral, and neurodegenerative consequences of chronic alcoholism are discussed.

Alkaloids↗