A single-day paradigm of self-regulated human cocaine administration.

UNLABELLED: Prior work by our group has shown the feasibility, safety, and validity of a multi-day, multi-dose paradigm of self-regulated cocaine administration in humans. The current work sought to consolidate these methods in a single-day design focused on reducing logistical complexity, decreasing research burden to human subjects, and increasing suitability for medication development designs. METHODS: Eleven experienced cocaine users participated in a 6-hour, single-day design, consisting of one safety/eligibility and three experimental cocaine periods (during which subjects were allowed to self-administer 8, 16, and 32 mg/70 kg cocaine doses under a fixed-ratio 1:5 minute timeout schedule). Changes in cocaine-induced cardiovascular response, self-administration behavior, and subjective effects were assessed. RESULTS: Procedures were well tolerated by participants, and no significant adverse events were noted. Significant (p < 0.05), changes in measures of cocaine self-administration (e.g., responses, infusions, interinfusion intervals, consumption, and plasma levels), cardiovascular response (HR), and subjective effects ("high") were observed. In contrast, cocaine-induced increases in other vital signs (e.g., SBP, DBP) and subjective effect measures (e.g., paranoia) did not differ between doses. CONCLUSIONS: These data support the safety, tolerability and validity of our single-day design. Depending on the application, such methods may afford advantages for assessing the self-regulation of cocaine administration behavior in humans (e.g., including medication development designs).

A multistudy analysis of the effects of early cocaine abstinence on sleep.

OBJECTIVE: To describe the sleep patterns of early cocaine abstinence in chronic users by polysomnographic and subjective measures. METHODS: 28 cocaine-dependent participants (ages 24-55) underwent polysomnographic sleep (PSG) recording on the 1st, 2nd and 3rd weeks of abstinence on a research dedicated inpatient facility. Objective measures of total sleep time, total REM time, slow wave sleep, sleep efficiency and a subjective measure (sleep quality) along with demographic data were collected from three different long term research studies over a five year period. Data were reanalysed to allow greater statistical power for comparisons. RESULTS: Progressive weeks of abstinence had main effects on all assessed PSG sleep measures showing decreased total sleep time, REM sleep, stages 1 and 2 sleep, and sleep efficiency; increases in sleep onset and REM latencies and a slight increase in slow-wave sleep time were also present. Total sleep time and slow wave sleep were negatively associated with years of cocaine use. Total sleep time was positively associated with the amount of current ethanol use. Sex differences were found with females having more total REM time and an increase at a near significance level in slow wave sleep. Subjective measures were reported as improving with increasing abstinence over the same time period. CONCLUSIONS: Chronic cocaine users show a general deterioration in objective sleep measures over a three-week period despite an increase in subjective overall sleep quality providing further evidence for "occult insomnia" during early cocaine abstinence.

Southeast Asian origins of five Hill Tribe populations and correlation of genetic to linguistic relationships inferred with genome-wide SNP data.

In Thailand, the term Hill Tribe is used to describe populations whose members traditionally practice slash and burn agriculture and reside in the mountains. These tribes are thought to have migrated throughout Asia for up to 5,000 years, including migrations through Southern China and/or Southeast Asia. There have been continuous migrations southward from China into Thailand for approximately the past thousand years and the present geographic range of any given tribe straddles multiple political borders. As none of these populations have autochthonous scripts, written histories have until recently, been externally produced. Northern Asian, Tibetan, and Siberian origins of Hill Tribes have been proposed. All purport endogamy and have nonmutually intelligible languages. To test hypotheses regarding the geographic origins of these populations, relatedness and migrations among them and neighboring populations, and whether their genetic relationships correspond with their linguistic relationships, we analyzed 2,445 genome-wide SNP markers in 118 individuals from five Thai Hill Tribe populations (Akha, Hmong, Karen, Lahu, and Lisu), 90 individuals from majority Thai populations, and 826 individuals from Asian and Oceanean HGDP and HapMap populations using a Bayesian clustering method. Considering these results within the context of results ofrecent large-scale studies of Asian geographic genetic variation allows us to infer a shared Southeast Asian origin of these five Hill Tribe populations as well ancestry components that distinguish among them seen in successive levels of clustering. In addition, the inferred level of shared ancestry among the Hill Tribes corresponds well to relationships among their languages.

A paradigm to investigate the regulation of cocaine self-administration in human cocaine users: a randomized trial.

RATIONALE: We recently conducted a pilot study supporting the feasibility, safety, and validity of a human laboratory model of ad libitum cocaine administration in which subjects self-selected the timing of infusions. The current study extends this work to include a randomized design with a test-retest component in a larger sample. OBJECTIVES: To investigate the regulation of cocaine intake by humans and its effects on subjective and cardiovascular responses. MATERIALS AND METHODS: Subjects were 14 non-treatment seeking volunteers (10 M, 4 F) with cocaine abuse/dependence. Subjects self-administered cocaine infusions (0, 8, 16, and 32 mg/70 kg) over a 2-h period under a fixed ratio 1, 5-min time-out schedule on 4 consecutive days. A fifth session was conducted at 16-mg dose to assess the paradigm's test-retest reliability. RESULTS: Subjects regulated their cocaine intake in a dose-dependent fashion. Self-reports of cocaine-related subjective effects (e.g., "high" and "stimulated") also varied in a dose-dependent way. Test-retest data and the randomized design support the conclusion that such effects are not due to tolerance or other experimental artifacts. CONCLUSION: The current study replicates prior work demonstrating the feasibility, safety, and validity of our human laboratory paradigm of cocaine administration in a larger sample using a randomized design. The current study also shows the test-retest reliability of these methods, establishing its utility for comparisons of experimental interventions (e.g., pharmacological treatments). Finally, the current study suggests that factors other than drug-induced euphoria (i.e., "high") contribute to the regulation of cocaine-taking behaviors in humans.

Elevated motor threshold in drug-free, cocaine-dependent patients assessed with transcranial magnetic stimulation.

BACKGROUND: Transcranial magnetic stimulation (TMS) provides a noninvasive method of examining cortical inhibitory and excitatory processes and cortical excitability in awake subjects. There is evidence from clinical and electroencephalographic (EEG) data that cortical excitability may be abnormal in some psychiatric populations. Chronic cocaine abuse influences a number of neurotransmitters that are involved in the excitatory/inhibitory balance of the cerebral cortex. This pilot study was conducted to ascertain the possible utility of TMS in examining cortical excitability in a population of chronic cocaine abusers. METHODS: The right and left motor thresholds of ten cocaine-dependent subjects, according to DSM-IV, and ten normal control subjects were examined using single pulse TMS. RESULTS: The resting motor thresholds resulting from stimulation of the right or the left motor cortical regions were significantly elevated in cocaine-dependent subjects compared with matched control subjects. CONCLUSIONS: These pilot data suggest that chronic cocaine use significantly alters cortical excitability in the direction of increased inhibition or decreased excitability. We hypothesize that this observation reflects adaptation to those effects of cocaine intoxication that promote cortical excitability and seizures.

A quantitative-trait analysis of human plasma-dopamine beta-hydroxylase activity: evidence for a major functional polymorphism at the DBH locus.

Dopamine-beta-hydroxylase (D beta H) catalyzes the conversion of dopamine to norepinephrine and is released from sympathetic neurons into the circulation. Plasma-D beta H activity varies widely between individuals, and a subgroup of the population has very low activity levels. Mounting evidence suggests that the DBH structural gene is itself the major quantitative-trait locus (QTL) for plasma-D beta H activity, and a single unidentified polymorphism may account for a majority of the variation in activity levels. Through use of both sequencing-based mutational analysis of extreme phenotypes and genotype/phenotype correlations in samples from African American, European American (EA), and Japanese populations, we have identified a novel polymorphism (--1021C-->T), in the 5' flanking region of the DBH gene, that accounts for 35%--52% of the variation in plasma-D beta H activity in these populations. In EAs, homozygosity at the T allele predicted the very low D beta H-activity trait, and activity values in heterozygotes formed an intermediate distribution, indicating codominant inheritance. Our findings demonstrate that --1021C-->T is a major genetic marker for plasma-D beta H activity and provide new tools for investigation of the role of both D beta H and the DBH gene in human disease.

Age-related decline in central serotonin transporter availability with [(123)I]beta-CIT SPECT.

Postmortem studies have provided limited and conflicting data regarding aging effects on the central serotonin transporter (SERT). The present study investigated the effect of age on SERT availability in the human brainstem and diencephalon with single photon emission computed tomography (SPECT) using the ligand [(123)I]2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane ([(123)I]beta-CIT). Healthy control subjects (n = 126) who ranged in age from 18 to 88 were injected with 6.0 +/- 0.8 (mean +/- SD) mCi [(123)I]beta-CIT and imaged 23.1 +/- 1.9 h later under equilibrium conditions. A ratio of specific to nondisplaceable brain uptake (i.e. , V(3)" = [brainstem-diencephalon -occipital]/occipital), a measure proportional to the binding potential (B(max)/K(D)), was derived. SERT availability (V(3)") showed a significant inverse correlation with age (r = -0.40, P < 0.0001). Linear regression analysis revealed that V(3)" declined by 29.5% over the age range 18 to 88, or approximately 4.2% per decade. These results demonstrate reductions in the availability of central SERT binding sites with age in living human subjects.

Genetic polymorphism at the CLOCK gene locus and major depression.

Genetic analysis in both mouse and Drosophila has indicated that the product of the CLOCK gene is an essential component of a circadian rhythm timing system. A single nucleotide polymorphism (SNP), T3111C, in the 3' flanking region of the human CLOCK gene has been identified. Homozygotes or heterozygotes for the 3111C allele have been reported to have higher mean scores on a measure of evening preference for activity (vs. morning preference) than subjects homozygous for the 3111T allele. Since major depression is hypothesized to be closely linked to circadian rhythms, we explored whether this polymorphism might be related to susceptibility to major depression. We also ascertained allele frequency in an African-American control population, to begin to evaluate population variation at this locus. CLOCK T3111C allele frequencies were determined in 280 European American (EA) subjects, 143 with a history of major depression and 137 screened controls, and in 58 African American (AA) screened control subjects, using a polymerase chain reaction (PCR) - restriction fragment length polymorphism (RFLP) method. There was no significant difference between EA depressed and control subjects in allele frequency. There was a significant difference in allele frequency between EA and AA subjects, demonstrating a potential for population stratification. In none of these groups were significant deviations from Hardy-Weinberg equilibrium found. The present data do not support an association between CLOCK gene alleles at the T3111C locus and major depression.

Elevated central serotonin transporter binding availability in acutely abstinent cocaine-dependent patients.

OBJECTIVE: Recent work has underscored the role of serotonergic neurotransmission in chronic neural adaptations to cocaine dependence. The authors tested for evidence of serotonergic dysfunction during acute abstinence from cocaine, a period of high risk for relapse in cocaine dependence. METHOD: Binding availability of dopamine transporters and serotonin transporters was measured in 15 cocaine-dependent subjects during acute abstinence and in 37 healthy comparison subjects by using [(123)I]beta-CIT and single photon emission computed tomography. RESULTS: Significant increases in diencephalic and brainstem serotonin transporter binding (16.7% and 31.6%, respectively) were observed in cocaine-dependent subjects. Brainstem serotonin transporter binding was significantly inversely correlated with age across diagnostic groups. CONCLUSIONS: These findings provide further evidence of serotonergic dysfunction during acute abstinence from chronic cocaine use. Age-related decline in brainstem serotonin transporter binding may underlie the poor response to selective serotonin reuptake inhibitor antidepressants seen in some elderly depressed patients.

A haplotype at the DBH locus, associated with low plasma dopamine beta-hydroxylase activity, also associates with cocaine-induced paranoia.

Low levels of dopamine beta-hydroxylase (DbetaH) protein in the plasma or cerebrospinal fluid (CSF) are associated with greater vulnerability to positive psychotic symptoms in several psychiatric disorders. DbetaH level is a stable, genetically controlled trait. DBH, the locus encoding DbetaH protein, is the major quantitative trait locus controlling plasma and CSF DbetaH levels. We therefore hypothesized that DBH variants or haplotypes, associated with low levels of DbetaH in the plasma, would also associate with greater vulnerability to cocaine-induced paranoia. To test this hypothesis, we first showed that a di-allelic variant, DBH*5'-ins/del, located approximately 3 kb 5' to the DBH transcriptional start site, significantly associates with plasma DbetaH activity in European-Americans (n = 66). Linkage disequilibrium analysis of that polymorphism and DBH*444g/a, another di-allelic variant associated with DbetaH levels, demonstrated that alleles of similar association to DbetaH levels are in positive disequilibrium. We then estimated DBH haplotype frequencies in cocaine-dependent European Americans rated for cocaine-induced paranoia (n = 45). As predicted, the low-DbetaH-associated haplotype, Del-a, was significantly more frequent (P = 0.0003) in subjects endorsing cocaine-induced paranoia (n = 29) than in those denying it (n = 16). Comparison to control haplotype frequencies (n = 145 healthy European-Americans) showed that the association predominantly reflected under-representation of Del-a haplotypes in those denying cocaine-induced paranoia. We conclude that: (a) the two DBH polymorphisms we studied are associated with plasma DBH levels; (b) those two polymorphisms are in significant linkage disequilibrium in European Americans, with alleles of similar association to DbetaH levels in positive disequilibrium; and (c) the haplotype associated with low DBH activity is also associated with cocaine-induced paranoia. Molecular Psychiatry (2000) 5, 56-63.

Limited efficacy of ketoconazole in treatment-refractory major depression.

The authors examined the efficacy of ketoconazole in 16 adults with treatment-refractory major depressive disorder. Subjects participated in a 6-week, double-blind, placebo-controlled trial. Assessments of mood were made using the Hamilton Rating Scale for Depression (HAM-D), the Beck Depression Inventory (BDI), and the Clinical Global Impression Scale (CGI). Results showed that none of eight patients randomly assigned to receive placebo and two of eight patients randomly assigned to receive ketoconazole met criteria for response. As a group, patients assigned to receive ketoconazole showed no significant reductions in HAM-D, BDI, or CGI scores during the 6-week trial compared with those receiving placebo. These findings suggest a limited efficacy for ketoconazole in patients with treatment-refractory major depression.

Reduced brain serotonin transporter availability in major depression as measured by [123I]-2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane and single photon emission computed tomography.

BACKGROUND: Prior research has suggested reductions in the density of serotonin transporter (SERT) binding sites in blood platelets and post-mortem brain tissue of depressed patients. We sought to determine whether patients with unipolar major depression have diminished SERT availability as assessed by both brainstem [123I] beta-CIT SPECT and platelet [3H]paroxetine binding. METHODS: Drug-free depressed and healthy subjects were injected with 211 +/- 22 MBq [123I] beta-CIT and imaged 24 +/- 2 h later under equilibrium conditions. A ratio of specific to nonspecific brain uptake (V3" = (brainstem-occipital)/occipital), a measure proportional to the binding potential (Bmax/Kd), was used for all comparisons. RESULTS: Results showed a statistically significant reduction in brainstem V3" values in depressed as compared to healthy subjects (3.1 +/- .9 vs. 3.8 +/- .8, p = .02). Platelet [3H]paroxetine binding was not altered (Bmax = 2389 +/- 484 vs. 2415 +/- 538 fmol/mg protein, p = .91) and was not significantly correlated with brainstem [123I] beta-CIT binding (r = -0.14, p = .48). CONCLUSIONS: These data are the first to suggest reductions in the density of brain SERT binding sites in living depressed patients. These findings provide further support for a preeminent role for alterations in serotonergic neurons in the pathophysiology of depression.

Lithium and desipramine versus desipramine alone in the treatment of severe major depression: a preliminary study.

Improvement following lithium augmentation is well-documented in depressed patients resistant to tricyclic antidepressants. However, response latency to lithium augmentation is extremely variable, suggesting other mechanisms may be involved. To evaluate whether long-term tricyclic treatment is necessary for lithium augmentation's effect, the rapidity and magnitude of response to lithium combined with desipramine from the start of treatment was compared to desipramine alone in severely depressed patients. Patients with DSM-III-R major depression were randomized to double-blind, placebo-controlled treatment with either lithium + desipramine or placebo + desipramine for 4 weeks. Response criteria were based on Hamilton Depression Rating Scale scores and global improvement. Analysis of covariance of Hamilton scores demonstrated that lithium + desipramine was superior to placebo + desipramine at week 1 (P < 0.009), week 2 (P < 0.028), and week 3 (P < 0.07), although not at week 4. There were more responders to the combination than to monotherapy (P < 0.042). These preliminary data suggest that lithium + desipramine may have some efficacy in severely depressed patients. Further studies with larger samples are needed to confirm these findings.

Imaging of the serotonergic system: interactions of neuroanatomical and functional abnormalities of depression.

For nearly three decades, evidence supporting a role for aberrant serotonergic function in the pathogenesis of depression has accumulated; however, only recently have methodologies and radiotracers suitable for in vivo clinical assessment of depression become available. To date, only a few neurochemical imaging studies have been performed in actively depressed subjects. A preliminary study using single photon emission computed tomography (SPECT) has demonstrated decreased levels of serotonin (5-HT) transporters in the midbrain regions of subjects with major depression. Analysis of the 5-HT2 receptor using positron emission tomography (PET) has suggested that this receptor may not be altered significantly in the depressed brain but may increase in response to antidepressant treatment. These findings are supported by studies in secondary "poststroke" depression that have shown that elevations in 5-HT2 receptor density correlated with the alleviation of symptoms of depressed mood. With the rapid development of novel PET and SPECT radiotracers, future studies of the serotonergic system that evaluate presynaptic (5-HT transporter) and postsynaptic (5-HT1A and 5-HT2A receptors) markers and the interaction of synaptic levels of 5-HT with these sites will make profound contributions to the understanding of the role of the serotonergic synapse in the pathophysiology of depression.

Dopamine beta-hydroxylase: two polymorphisms in linkage disequilibrium at the structural gene DBH associate with biochemical phenotypic variation.

Levels of the enzyme dopamine beta-hydroxylase (DbetaH) in the plasma and cerebrospinal fluid (CSF) are closely related biochemical phenotypes. Both are under strong genetic control. Linkage and association studies suggest the structural gene encoding DbetaH (locus name, DBH) is a major locus influencing plasma activity of DbetaH. This study examined relationships of DBH genotype determined at two polymorphic sites (a previously described GT repeat, referred to as the DBH STR and a single-base substitution at the 3' end of DBH exon 2, named DBH*444 g/a), to CSF levels of DbetaH protein in European-American schizophrenic patients, and to plasma DbetaH activity in European-American patients with mood or anxiety disorders. We also investigated linkage disequilibrium (LD) between the polymorphisms in the pooled samples from those European-American subjects (n=104). Alleles of DBH*444 g/a were associated with differences in mean values of CSF DbetaH levels. Alleles at both polymorphisms were associated with plasma DbetaH activity. Significant LD was observed between respective alleles with similar apparent influence on biochemical phenotype. Thus, allele A3 of the DBH STR was in positive LD with DBH*444a, and both alleles were associated with lower plasma DbetaH activity. DBH STR allele A4 was in positive LD with DBH*444 g, and both alleles were associated with higher plasma DbetaH activity. The results confirm that DBH is a major quantitative trait locus for plasma DbetaH activity, and provide the first direct evidence that DBH also influences CSF DbetaH levels. Both polymorphisms examined in this study appear to be in LD with one or more functional polymorphisms that mediate the influence of allelic variation at DBH on DbetaH biochemical phenotypic variation

[123I]beta-CIT SPECT imaging of dopamine transporter availability after mazindol administration in human cocaine addicts.

The in vivo potency of mazindol for binding to striatal dopamine transporters (DAT) was assessed by [123I]beta-CIT ([123I]2beta-carbomethoxy-3beta-(4-iodophenyl)tropane) single photon emission computed tomography (SPECT). Cocaine-dependent subjects (n = 12) underwent three SPECT scans; one before, between, and after subchronic (1 week) administration of 2 mg/day and 4 mg/day mazindol. For each scan, subjects were injected with [123I]beta-CIT and imaged 24 h later under equilibrium conditions. Results showed a statistically significant main effect of mazindol dose (df = 2, F = 10.30, P < 0.001, repeated measures ANOVA) in reducing the specific to non-displaceable equilibrium partition coefficient, V3'' (a measure proportional to DAT binding potential). Regression analysis of the logit transformed data enabled estimation of the 50% displacement dose of mazindol (ED50 = 30mg/day). These data suggest that low doses of mazindol (i.e., 2-4 mg) occupy a small percentage (i.e., < 25%) of DAT in human cocaine abusers and that much higher, potentially intolerable doses (i.e., > or = 30 mg/day) may be required to antagonize significantly cocaine binding in vivo.

Elevated striatal dopamine transporters during acute cocaine abstinence as measured by [123I] beta-CIT SPECT.

OBJECTIVE: The authors examined whether striatal dopamine transporters were altered in acutely (96 hours or less) abstinent cocaine-abusing subjects, as suggested by postmortem studies. METHOD: [123I] beta-CIT and single photon emission computed tomography were used to assess striatal dopamine transporter levels in 28 cocaine-abusing subjects and 24 comparison subjects matched as a group for age and gender. RESULTS: Results showed a significant (approximately 20%) elevation in striatal V3" values in acutely abstinent cocaine-abusing subjects relative to comparison subjects. An inverse correlation between dopamine transporter level and Hamilton Depression Rating Scale score was also observed. CONCLUSIONS: These findings indicate more modest elevations in striatal dopamine transporters in cocaine-abusing subjects than noted in previous postmortem reports and suggest a possible relationship between cocaine-related depression and dopamine transporter binding.

Plasma homovanillic acid and the dopamine transporter during cocaine withdrawal.

BACKGROUND: Plasma homovanillic acid (HVA) has been used as a measure of central dopaminergic activity but the validity of this method continues to be investigated. We used single photon emission tomography (SPECT) assessment of the dopamine (DA) transporter for comparison with plasma HVA in subjects at varying stages of abstinence from cocaine. METHODS: Nineteen subjects were studied in two separate treatment sites. Plasma HVA and methoxyhydroxyphenethyleneglycol (MHPG) were measured by gas chromatography-mass spectroscopy (GC-MS). The DA transporter was quantified using the SPECT ligand [123I]B-CIT. RESULTS: At 2 weeks of abstinence and beyond there was an increasing positive correlation between plasma HVA and the SPECT measurement of the DA transporter (V3"). CONCLUSIONS: Plasma HVA may be more likely to reflect DA transporter density in the striatum when there is not a major drug-related change in the DA system.

The neurobiology of tryptophan depletion in depression: effects of intravenous tryptophan infusion.

BACKGROUND: Previous work has suggested that acute depletion of the serotonin (5-HT) precursor tryptophan (TRP) causes transient compensatory changes in the 5-HT system that might be exploited for their antidepressant effects. In this study, neuroendocrine and mood responses to intravenous (i.v.) infusion of TRP were examined in order to evaluate central 5-HT function in depressed patients undergoing acute TRP depletion. METHODS: Thirty-eight drug-free patients with DSM-III-R major depression participated. Each patient underwent two randomized, double-blind TRP depletion tests, one sham and one active. At the estimated time of maximum TRP depletion, each patient received an i.v. infusion of TRP 100 mg/kg. Blood was obtained for serum cortisol, prolactin, and growth hormone. Mood was assessed using standardized rating scales. RESULTS: The cortisol response to i.v. TRP was significantly greater during TRP depletion than during sham depletion. Depressive symptoms showed a tendency to decrease after i.v. TRP following active, but not sham, TRP depletion. CONCLUSIONS: These findings are consistent with the present hypothesis and previous evidence that acute TRP depletion in drug-free depressed patients induces compensatory upregulation of postsynaptic 5-HT receptors. These changes are insufficient to serve as a means of effecting clinical improvement, but suggest that the antidepressant properties of rapid, marked manipulations of 5-HT function warrant further study.