Altering cortisol level does not change the pleasurable effects of methamphetamine in humans

Exploring peripheral biomarkers in psychostimulant use: A systematic review on neurotrophins, stress-related hormones, oxidative stress molecules and genetic factors

BACKGROUND

This systematic review aims to comprehensively explore the impact of psychostimulant substances on neurotrophic and inflammatory pathways, including brain-derived neurotrophic factor (BDNF), pro-BDNF, cortisol, dehydroepiandrosterone sulfate (DHEAS), thiobarbituric acid reactive substances (TBARS), interleukins, and the role of genetic factors. The study seeks to address existing gaps in the literature by providing a thorough evaluation of neurotrophic and inflammatory system alterations associated with different stages of psychostimulant dependence for a more nuanced understanding of substance use disorder (SUD) neurobiology.

METHODS

A systematic review was conducted in PubMed, Scopus, and Web of Science databases following the PRISMA guidelines. The research encompasses 50 studies with a participant pool totaling 6792 individuals using psychostimulant substances.

RESULTS

Key findings include diverse impacts of cocaine on BDNF levels, mainly consisting of their significant increase during withdrawal. In contrast, NGF showed an opposite behavior, reducing during withdrawal. Cortisol and DHEAS levels exhibited relevant increases after psychostimulant use, while TBARS showed conflicting results. Genetic investigations predominantly focused on the Val66Met polymorphism of the BDNF gene, revealing associations with susceptibility to stimulant addiction.

CONCLUSIONS

Neurotrophins and inflammatory molecules play a significant role in the pathophysiological mechanisms following psychostimulant use. A better understanding of their complex interplay could aid clinicians in identifying biomarkers of different disease stages. Moreover, clinical interventions designed to interfere with neurotrophic and inflammatory pathways could possibly lead to craving-modulatory strategies and reduce pathological neuronal and systemic consequences of psychostimulant use.

The association of FKBP5 polymorphisms with the severity of depressive disorder in patients with methamphetamine use disorders

Background

Co-occurring depressive disorder (DD) in patients of methamphetamine use disorder (MAUD) impacts the diagnosis, treatment, and prognosis of the disease. Although FKBP5 has been associated with a variety of psychiatric disorders, whether FKBP5 influences depression susceptibility in MAUD is unknown so far.

Methods

Here, we sequenced six FKBP5 single-nucleotide polymorphism (SNP) sites (rs4713916, rs6926133, rs9470080, rs737054, rs4713902, and rs9470079) in 282 methamphetamine users. MAUD and DD were evaluated by clinical questionnaires. SPSS was used to analyze the relationship between FKBP5 SNPs and DD in individuals with MAUD.

Results

Of the 282 methamphetamine users, 161 individuals met the MAUD criteria, and among them, 50 patients (31.1%) had DD co-occurring. Importantly, the incidence of DD in individuals with MAUD was 3.314 times greater than that of the methamphetamine users who did not meet the MAUD criteria (p < 0.001). Although none of the six SNPs of FKBP5 were correlated with the co-occurrence of DD in the population with MAUD, two FKBP5 alleles (rs4713916A and rs6926133A) were substantially associated with the higher DD scores in patients with MAUD (p < 0.05). Moreover, those with the two risk alleles do not have much higher scores than those with a single risk allele, and the strong linkage disequilibrium of the two SNPs may be the underlying cause of this result. Despite having weak linkage disequilibrium with either rs4713916 or rs6926133, FKBP5 rs9470079 became risky when paired with either.

Conclusion

The results of this study revealed that the FKBP5 risk alleles (rs4713916A and rs6926133A) were associated with a greater probability of severe DD in patients with MAUD. These findings here would help with the development of biological early warning markers and the creation of personalized treatment strategies for MAUD.

Striatal miR-183-5p inhibits methamphetamine-induced locomotion by regulating glucocorticoid receptor signaling

MicroRNA (miRNA)-mediated striatal gene regulation may play an important role in methamphetamine (METH) addiction. This study aimed to identify changes in novel miRNAs and their target genes during METH self-administration and investigate their roles in METH-induced locomotion. RNA sequencing analysis revealed that mir-183-5p was upregulated in the striatum of METH self-administered rats, and target gene prediction revealed that the glucocorticoid receptor (GR) gene, Nr3c1, was a potential target gene for mir-183-5p. We confirmed that single and repeated METH administrations increased METH-induced locomotion and plasma corticosterone levels in rats. Additionally, increased miR-185-5p expression and decreased GR gene expression were observed only in the repeated-METH-injection group but not in the single-injection group. We then investigated the effects of miR-183-5p on METH-induced locomotion using a miR-183-5p mimic and inhibitor. Injection of a mir-183-5p mimic in the striatum of rats attenuated METH-induced locomotion, whereas injection of a miR-183-5p inhibitor enhanced the locomotor activity in METH-administered rats. Furthermore, the miR-183-5p mimic reduced the phosphorylation of tyrosine hydroxylase (TH) whereas the inhibitor increased it. Taken together, these results indicate that repeated METH injections increase striatal miR-183-5p expression and regulate METH-induced locomotion by regulating GR expression in rats, thereby suggesting a potential role of miR-183-5p as a novel regulator of METH-induced locomotion.

Methamphetamine, amphetamine, and aggression in humans: A systematic review of drug administration studies

The relationship between amphetamine use and aggressive or violent behaviour is unclear. This review examined laboratory data collected in humans, who were administered an acute dose of amphetamine or methamphetamine, in order to investigate the link between amphetamines and aggression. It is registered with PROSPERO (CRD42019127711). Included in the analysis are data from twenty-eight studies. Behavioural and/or subjective measures of aggression were assessed in one thousand and sixty-nine research participants, with limited amphetamine-use histories, following a single amphetamine dose (0-35mg). The available published evidence indicates that neither amphetamine nor methamphetamine acutely increased aggression as assessed by traditional laboratory measures. Future research should assess supratherapeutic amphetamine doses as well as include a broader range of multiple aggression measures, facilitating simultaneous assessment of the various components that comprise this complex, multifaceted construct.

Drug-Induced Craving for Methamphetamine Is Associated With Neural Methamphetamine Cue Reactivity

OBJECTIVE

Drug craving serves as the major motivator to propagate drug use and is thought to elicit relapse in abstinent individuals. Although craving for methamphetamine has been investigated using both laboratory and neuroimaging methodologies, the relationship between drug-induced craving and neural responses to methamphetamine cues has yet to be explored. Therefore, the present study investigated whether methamphetamine-induced craving responses in the laboratory were associated with neural response to methamphetamine cues.

METHOD

Non-treatment-seeking individuals with methamphetamine use disorder (n = 15) completed two sessions, one in the laboratory where they underwent a methamphetamine infusion, and one in the magnetic resonance imaging scanner where they viewed methamphetamine cues. Participants reported their craving for methamphetamine over the course of the laboratory session. Analyses examined the association between peak ratings of methamphetamine-induced craving and neural activation to methamphetamine cues.

RESULTS

In individuals with a methamphetamine use disorder, methamphetamine-induced craving was positively associated with neural methamphetamine cue reactivity in the precuneus, putamen, and ventromedial prefrontal cortex (Z > 2.3, p < .05).

CONCLUSIONS

There is a shared neurobiology underlying cue- and drug-induced craving in individuals with methamphetamine use disorder. Treatments that disrupt this circuitry may decrease craving and help prevent relapse.

Effects of lisdexamfetamine on plasma steroid concentrations compared with d-amphetamine in healthy subjects: A randomized, double-blind, placebo-controlled study

The novel d-amphetamine prodrug lisdexamfetamine is applied to treat attention-deficit/hyperactivity disorder (ADHD). d-Amphetamine releases dopamine and norepinephrine and stimulates the hypothalamic-pituitary-adrenal (HPA) axis, which may contribute to its reinforcing effects and risk of abuse. However, no data is currently available on the effects of lisdexamfetamine on circulating steroids. This randomized, double-blind, placebo-controlled, cross-over study evaluated the effects of equimolar doses of d-amphetamine (40 mg) and lisdexamfetamine (100 mg) and placebo on circulating steroids in 24 healthy subjects. Plasma steroid and d-amphetamine levels were determined up to 24 h. Delayed increase and peak levels of plasma d-amphetamine concentrations were observed following lisdexamfetamine treatment compared with d-amphetamine administration, however the maximal concentrations and total exposure (area under the curve [AUC]) were similar. Lisdexamfetamine and d-amphetamine significantly enhanced plasma levels of adrenocorticotropic hormone, glucocorticoids (cortisol, cortisone, corticosterone, 11-dehydrocorticosterone, and 11-deoxycortisol), androgens (dehydroepiandrosterone, dehydroepiandrosterone sulfate, and Δ4-androstene-3,17-dione [androstenedione]), and progesterone (only in men) compared with placebo. Steroid concentration-time curves were shifted to later time points due to a non-significantly later onset following lisdexamfetamine administration than after d-amphetamine, however maximal plasma steroid concentrations and AUCs did not differ between the active treatments. None of the active treatments altered plasma levels of the mineralocorticoids aldosterone and 11-deoxycorticosterone or the androgen testosterone compared with placebo. The effects of the amphetamines on glucocorticoid production were similar to those that were previously reported for methylphenidate (60 mg) but weaker than those for the serotonin releaser 3,4-methylenedioxymethamphetamine (MDMA; 125 mg) or direct serotonin receptor agonist lysergic acid diethylamide (LSD; 0.2 mg). Lisdexamfetamine produced comparable HPA axis activation and had similar pharmacokinetics than d-amphetamine, except for a delayed time of onset. Thus, serotonin (MDMA, LSD) may more effectively stimulate the HPA axis than dopamine and norepinephrine (D-amphetamine).

Drug-induced stress responses and addiction risk and relapse

A number of studies have assessed the effects of psychoactive drugs on stress biology, the neuroadaptations resulting from chronic drug use on stress biology, and their effects on addiction risk and relapse. This review mainly covers human research on the acute effects of different drugs of abuse (i.e., nicotine, cannabis, psychostimulants, alcohol, and opioids) on the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) responses. We review the literature on acute peripheral stress responses in naïve or light recreational users and binge/heavy or chronic drug users. We also discuss evidence of alterations in tonic levels, or tolerance, in the latter relative to the former and associated changes in the phasic stress responses. We discuss the impact of the stress system tolerance in heavy users on their response to drug- and stress-related cue responses and craving as compared to control subjects. A summary is provided of the effects of glucocorticoid responses and their adaptations on brain striatal and prefrontal cortices involved in the regulation of drug seeking and relapse risk. Finally, we summarize important considerations, including individual difference factors such as gender, co-occurring drug use, early trauma and adversity and drug use history and variation in methodologies, that may further influence the effects of these drugs on stress biology.

The sigma-1 receptor as a regulator of dopamine neurotransmission: A potential therapeutic target for methamphetamine addiction

Methamphetamine (METH) abuse is a major public health issue around the world, yet there are currently no effective pharmacotherapies for the treatment of METH addiction. METH is a potent psychostimulant that increases extracellular dopamine levels by targeting the dopamine transporter (DAT) and alters neuronal activity in the reward centers of the brain. One promising therapeutic target for the treatment of METH addiction is the sigma-1 receptor (σ1R). The σ1R is an endoplasmic reticulum-localized chaperone protein that is activated by cellular stress, and, unique to this chaperone, its function can also be induced or inhibited by different ligands. Upon activation of this unique "chaperone receptor", the σ1R regulates a variety of cellular functions and possesses neuroprotective activity in the brain. Interestingly, a variety of σ1R ligands modulate dopamine neurotransmission and reduce the behavioral effects of METH in animal models of addictive behavior, suggesting that the σ1R may be a viable therapeutic target for the treatment of METH addiction. In this review, we provide background on METH and the σ1R as well as a literature review regarding the role of σ1Rs in modulating both dopamine neurotransmission and the effects of METH. We aim to highlight the complexities of σ1R pharmacology and function as well as the therapeutic potential of the σ1R as a target for the treatment of METH addiction.

Short circuit: Disaggregation of adrenocorticotropic hormone and cortisol levels in HIV-positive, methamphetamine-using men who have sex with men

OBJECTIVE

This study examined if methamphetamine use alone (METH + HIV-) and methamphetamine use in combination with HIV (METH + HIV+) were associated with hypothalamic-pituitary-adrenal (HPA) axis dysregulation as well as insulin resistance relative to a nonmethamphetamine-using, HIV-negative comparison group (METH-HIV-).

METHODS

Using an intact groups design, serum levels of HPA axis hormones in 46 METH + HIV- and 127 METH + HIV+ men who have sex with men (MSM) were compared to 136 METH-HIV- men.

RESULTS

There were no group differences in prevailing adrenocorticotropic hormone (ACTH) or cortisol levels, but the association between ACTH and cortisol was moderated by METH + HIV+ group (β = -0.19, p < .05). Compared to METH-HIV- men, METH + HIV+ MSM displayed 10% higher log₁₀ cortisol levels per standard deviation lower ACTH. Both groups of methamphetamine-using MSM had lower insulin resistance and greater syndemic burden (i.e., sleep disturbance, severe depression, childhood trauma, and polysubstance use disorder) compared to METH-HIV- men. However, the disaggregated functional relationship between ACTH and cortisol in METH + HIV+ MSM was independent of these factors.

CONCLUSIONS

Further research is needed to characterize the bio-behavioral pathways that explain dysregulated HPA axis functioning in HIV-positive, methamphetamine-using MSM.

Acute Effects of Lysergic Acid Diethylamide on Circulating Steroid Levels in Healthy Subjects

Lysergic acid diethylamide (LSD) is a serotonin 5-hydroxytryptamine-2A (5-HT2A ) receptor agonist that is used recreationally worldwide. Interest in LSD research in humans waned after the 1970s, although the use of LSD in psychiatric research and practice has recently gained increasing attention. LSD produces pronounced acute psychedelic effects, although its influence on plasma steroid levels over time has not yet been characterised in humans. The effects of LSD (200 μg) or placebo on plasma steroid levels were investigated in 16 healthy subjects using a randomised, double-blind, placebo-controlled, cross-over study design. Plasma concentration-time profiles were determined for 15 steroids using liquid-chromatography tandem mass-spectrometry. LSD increased plasma concentrations of the glucocorticoids cortisol, cortisone, corticosterone and 11-dehydrocorticosterone compared to placebo. The mean maximum concentration of LSD was reached at 1.7 h. Mean peak psychedelic effects were reached at 2.4 h, with significant alterations in mental state from 0.5 h to > 10 h. Mean maximal concentrations of cortisol and corticosterone were reached at 2.5 h and 1.9 h, and significant elevations were observed 1.5-6 h and 1-3 h after drug administration, respectively. LSD also significantly increased plasma concentrations of the androgen dehydroepiandrosterone but not other androgens, progestogens or mineralocorticoids compared to placebo. A close relationship was found between plasma LSD concentrations and changes in plasma cortisol and corticosterone and the psychotropic response to LSD, and no clockwise hysteresis was observed. In conclusion, LSD produces significant acute effects on circulating steroids, especially glucocorticoids. LSD-induced changes in circulating glucocorticoids were associated with plasma LSD concentrations over time and showed no acute pharmacological tolerance.

Methamphetamine and the hypothalamic-pituitary-adrenal axis

Psychostimulants such as methamphetamine (MA) induce significant alterations in the function of the hypothalamic-pituitary-adrenal (HPA) axis. These changes in HPA axis function are associated with altered stress-related behaviors and might contribute to addictive processes such as relapse. In this mini-review we discuss acute and chronic effects of MA (adult and developmental exposure) on the HPA axis, including effects on HPA axis associated genes/proteins, brain regions, and behaviors such as anxiety and depression. A better understanding of the mechanisms through which MA affects the HPA axis may lead to more effective treatment strategies for MA addiction.

Effects of acute methamphetamine on emotional memory formation in humans: encoding vs consolidation

Understanding how stimulant drugs affect memory is important for understanding their addictive potential. Here we examined the effects of acute d-methamphetamine (METH), administered either before (encoding phase) or immediately after (consolidation phase) study on memory for emotional and neutral images in healthy humans. Young adult volunteers (N = 60) were randomly assigned to either an encoding group (N = 29) or a consolidation group (N = 31). Across three experimental sessions, they received placebo and two doses of METH (10, 20 mg) either 45 min before (encoding) or immediately after (consolidation) viewing pictures of emotionally positive, neutral, and negative scenes. Memory for the pictures was tested two days later, under drug-free conditions. Half of the sample reported sleep disturbances following the high dose of METH, which affected their memory performance. Therefore, participants were classified as poor sleepers (less than 6 hours; n = 29) or adequate sleepers (6 or more hours; n = 31) prior to analyses. For adequate sleepers, METH (20 mg) administered before encoding significantly improved memory accuracy relative to placebo, especially for emotional (positive and negative), compared to neutral, stimuli. For poor sleepers in the encoding group, METH impaired memory. METH did not affect memory in the consolidation group regardless of sleep quality. These results extend previous findings showing that METH can enhance memory for salient emotional stimuli but only if it is present at the time of study, where it can affect both encoding and consolidation. METH does not appear to facilitate consolidation if administered after encoding. The study also demonstrates the important role of sleep in memory studies.

Acute effects of 3,4-methylenedioxymethamphetamine and methylphenidate on circulating steroid levels in healthy subjects

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') and methylphenidate are widely used psychoactive substances. MDMA primarily enhances serotonergic neurotransmission, and methylphenidate increases dopamine but has no serotonergic effects. Both drugs also increase norepinephrine, resulting in sympathomimetic properties. Here we studied the effects of MDMA and methylphenidate on 24-hour plasma steroid profiles. 16 healthy subjects (8 men, 8 women) were treated with single doses of MDMA (125 mg), methylphenidate (60 mg), MDMA + methylphenidate, and placebo on 4 separate days using a cross-over study design. Cortisol, cortisone, corticosterone, 11-dehydrocorticosterone, aldosterone, 11-deoxycorticosterone, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), androstenedione, and testosterone were repeatedly measured up to 24 h using liquid chromatography-tandem mass spectroscopy. MDMA significantly increased the plasma concentrations of cortisol, corticosterone, 11-dehydrocorticosterone, and 11-deoxycorticosterone and also tended to moderately increase aldosterone levels compared with placebo. MDMA also increased the sum of cortisol + cortisone and the cortisol/cortisone ratio, consistent with an increase in glucocorticoid production. MDMA did not alter the levels of cortisone, DHEA, DHEAS, androstenedione, or testosterone. Methylphenidate did not affect any of the steroid concentrations, and it did not change the effects of MDMA on circulating steroids. In summary, the serotonin releaser MDMA has acute effects on circulating steroids. These effects are not observed after stimulation of the dopamine and norepinephrine systems with methylphenidate. The present findings support the view that serotonin rather than dopamine and norepinephrine mediates the acute pharmacologically induced stimulation of the hypothalamic-pituitary-adrenal axis in the absence of other stressors.

Inhibition of MDMA-induced increase in cortisol does not prevent acute impairment of verbal memory

Background

Ecstasy use is commonly linked with memory deficits in abstinent ecstasy users. Similar impairments are being found during ecstasy intoxication after single doses of ± 3,4 metylenedioxymethamphetamine (MDMA). The concordance of memory impairments during intoxication and abstinence suggests a similar neuropharmacological mechanism underlying acute and chronic memory impairments. The mechanism underlying this impairment is to date not known. We hypothesized that cortisol might play an important role in this mechanism as cortisol, implicated in the regulation of memory performance, can be brought out of balance by stressors like MDMA.

Methods

In the present study, we aimed to block the MDMA-induced acute memory defect by giving participants a cortisol synthesis inhibitor (metyrapone) together with a single dose of MDMA. Seventeen polydrug MDMA users entered this placebo-controlled within subject study with four treatment conditions. The treatments consisted of MDMA (75 mg) and metyrapone (750 mg), alone and in combination, and double placebo. Pre-treatment with metyrapone or Placebo occurred 1 h prior to MDMA or Placebo administration. Memory performance was tested at peak drug concentrations by means of several memory tests. Cortisol levels were determined in blood and oral fluid; this served as a control measure to see whether manipulations were effective.

Results

Main findings indicated that whereas treatment with metyrapone blocked the expected MDMA-induced increase in cortisol levels in blood, it did not prevent the MDMA-induced memory deficit from happening.

Conclusion

We therefore conclude that MDMA-induced increments in cortisol concentrations are not related to MDMA-induced memory impairments.

Methamphetamine use: a comprehensive review of molecular, preclinical and clinical findings

Methamphetamine (MA) is a highly addictive psychostimulant drug that principally affects the monoamine neurotransmitter systems of the brain and results in feelings of alertness, increased energy and euphoria. The drug is particularly popular with young adults, due to its wide availability, relatively low cost, and long duration of psychoactive effects. Extended use of MA is associated with many health problems that are not limited to the central nervous system, and contribute to increased morbidity and mortality in drug users. Numerous studies, using complementary techniques, have provided evidence that chronic MA use is associated with substantial neurotoxicity and cognitive impairment. These pathological effects of the drug, combined with the addictive properties of MA, contribute to a spectrum of psychosocial issues that include medical and legal problems, at-risk behaviors and high societal costs, such as public health consequences, loss of family support and housing instability. Treatment options include pharmacological, psychological or combination therapies. The present review summarizes the key findings in the literature spanning from molecular through to clinical effects.

Effects of the combination of metyrapone and oxazepam on cocaine craving and cocaine taking: a double-blind, randomized, placebo-controlled pilot study

Although cocaine dependence affects an estimated 1.6 million people in the USA, there are currently no medications approved for the treatment of this disorder. Experiments performed in animal models have demonstrated that inhibitors of the stress response effectively reduce intravenous cocaine self-administration. This exploratory, double-blind, placebo-controlled study was designed to assess the safety and efficacy of combinations of the cortisol synthesis inhibitor metyrapone, and the benzodiazepine oxazepam, in 45 cocaine-dependent individuals. The subjects were randomized to a total daily dose of 500 mg metyrapone/20 mg oxazepam (low dose), a total daily dose of 1500 mg metyrapone/20 mg oxazepam (high dose), or placebo for 6 weeks of treatment. The outcome measures were a reduction in cocaine craving and associated cocaine use as determined by quantitative measurements of the cocaine metabolite benzoylecgonine (BE) in urine at all visits. Of the randomized subjects, 49% completed the study. The combination of metyrapone and oxazepam was well tolerated and tended to reduce cocaine craving and cocaine use, with significant reductions at several time points when controlling for baseline scores. These data suggest that further assessments of the ability of the metyrapone and oxazepam combination to support cocaine abstinence in cocaine-dependent subjects are warranted.

Developing biomarkers for methamphetamine addiction

There are an estimated 11.7 million methamphetamine (MA) abusers in the United States and epidemics of MA addiction are occurring worldwide. In our human laboratory and outpatient clinical trials we use innovative methods to quantify the severity of MA addiction and test biomarkers that may predict response to therapy or risk of relapse. One potential biomarker of addiction is the quantity of abused drug intake. Qualitative urinalysis is used in clinical trials and during treatment but provides only a binary outcome measure of abuse. Using non-pharmacologic doses of deuterium labeled l-MA we have developed a continuous quantitative measure to estimate the bioavailable amount of MA addicts ingest. Brain Derived Neurotrophic Factor is a neurotrophin that encourages growth and differentiation of new neurons and synapses. Low BDNF levels are seen in many addictive disorders and BDNF is elevated in recovering MA addicts, suggesting BDNF may be a marker of MA addiction. We are investigating the effects of controlled doses of MA on BDNF levels and gene regulation and measuring BDNF in our clinical trials. We believe both patients and clinical researches will benefit from the addition of new, objective and quantifiable outcome measures that reflect disease severity and recovery from addiction.

The clinical pharmacology of intranasal l-methamphetamine

Background

We studied the pharmacology of l-methamphetamine, the less abused isomer, when used as a nasal decongestant.

Methods

12 subjects self-administered l-methamphetamine from a nonprescription inhaler at the recommended dose (16 inhalations over 6 hours) then at 2 and 4 (32 and 64 inhalations) times this dose. In a separate session intravenous phenylephrine (200 μg) and l-methamphetamine (5 mg) were given to define alpha agonist pharmacology and bioavailability. Physiological, cardiovascular, pharmacokinetic, and subjective effects were measured.

Results

Plasma l-methamphetamine levels were often below the level of quantification so bioavailability was estimated by comparing urinary excretion of the intravenous and inhaled doses, yielding delivered dose estimates of 74.0 ± 56.1, 124.7 ± 106.6, and 268.1 ± 220.5 μg for ascending exposures (mean 4.2 ± 3.3 μg/inhalation). Physiological changes were minimal and not dose-dependent. Small decreases in stroke volume and cardiac output suggesting mild cardiodepression were seen.

Conclusion

Inhaled l-methamphetamine delivered from a non-prescription product produced minimal effects but may be a cardiodepressant.

CP-154,526, a CRF type-1 receptor antagonist, attenuates the cue-and methamphetamine-induced reinstatement of extinguished methamphetamine-seeking behavior in rats

RATIONALE

Previous studies from our laboratory and others have indicated a role for the hypothalamo-pituitary-adrenal (HPA) axis in the extinction/reinstatement animal model of cocaine relapse

OBJECTIVE

This present study was designed to investigate the potential role for the HPA axis in the cue- and methamphetamine-induced reinstatement of extinguished methamphetamine-seeking behavior by determining the effects of ketoconazole and the corticotropin-releasing hormone (CRF) type 1 receptor antagonist, CP-154,526, on these behaviors.

MATERIALS AND METHODS

Male Wistar rats were trained to self-administer methamphetamine (0.03 mg/kg/infusion). The delivery of methamphetamine was paired with the presentation of a tone and the illumination of a house light. Once stable responding was reached, the rats were placed into extinction. The effects of pretreatment with ketoconazole (25, 50, or 100 mg/kg, i.p.) or CP-154,526 (20 or 40 mg/kg, i.p.; 3 micro g, i.c.v) on cue-induced reinstatement were then evaluated.

RESULTS

Cue-induced reinstatement was not significantly attenuated by pretreatment with peripherally administered CP-154,526 or by pretreatment with ketoconazole. However, centrally administered CP-154,526 (3 micro g, i.c.v.) significantly attenuated cue-induced reinstatement. In a separate group of rats, CP-154,526 (20 mg/kg, i.p.) attenuated methamphetamine-induced reinstatement (0.12 mg/kg priming infusion); whereas a higher dose (40 mg/kg) was necessary to attenuate reinstatement induced by a priming infusion of 0.24 mg/kg/infusion. Ketoconazole (50 mg/kg) did not affect reinstatement induced by a 0.12 mg/kg priming infusion and, therefore, was not tested at the higher methamphetamine priming dose.

CONCLUSIONS

These data suggest an important role for CRF in the cue- and methamphetamine-induced reinstatement of extinguished methamphetamine-seeking behavior.

Human methamphetamine pharmacokinetics simulated in the rat: single daily intravenous administration reveals elements of sensitization and tolerance

We developed a computer-controlled intravenous methamphetamine (METH) administration procedure (dynamic infusion), which enables us to compensate for an important pharmacokinetic difference between rats and humans by imposing a 12-h half-life for the drug in rats. Dynamic infusion of 0.5 mg/kg METH produced a pharmacokinetic profile that closely simulates the METH exposure pattern in humans, including an apparent half-life of 11.6+/-1.3 h, and an area under the concentration vs time curve of 9.4 microM h, about 20-fold larger than results obtained with typical rat pharmacokinetics. Using this procedure, METH produced a prolonged behavioral stimulation and elevation in caudate extracellular dopamine (DA). Both the behavioral and the DA effects exhibited tolerance to the sustained plasma METH exposure. Single daily dynamic infusion of 0.5 mg/kg METH for 15 days resulted in a progressive enhancement of the behavioral response until about Day 10. On subsequent days, in addition to continued evidence of sensitization, tolerance in the form of a marked decrease in the duration of the behavioral activation became a prominent feature of the response. Qualitative changes in the behavior also emerged. Resumption of METH treatment following 4 days of withdrawal revealed that sensitization was apparent during the first dynamic infusion, and that tolerance re-emerged within two additional days of drug administration. These results showed that a human-like METH exposure pattern produced behavioral and striatal DA response profiles that are both quantitatively and qualitatively different from the effects typically observed with single daily METH injections in rats. Thus, simulation of human METH exposure patterns may be a critical prerequisite to identifying mechanisms relevant to the chronic use of this drug in humans.

Repeated psychological stress testing in stimulant-dependent patients

Decreasing response to stress has been one goal of interventions aimed at reducing relapse to substances of abuse. A laboratory stress test that can be repeated would be helpful in testing the efficacy of interventions in decreasing the response to stress before more extensive trials are begun. The effects of two types of psychological stress tests, the Trier Social Stress Test (TSST) and a stress imagery test, on psychological, physiological, and hormonal responses (salivary cortisol and DHEA) were examined when each test was given twice to cocaine- or methamphetamine-dependent human subjects, 24 of whom completed at least one session. The stress imagery test produced significant changes in several of the subjective response measures in both first and second sessions, including several measures of negative affect and a craving measure. The TSST produced significant changes only in the second session. The stress imagery protocol showed better replicability across two sessions. Cocaine users and methamphetamine users did not respond similarly in their craving responses. Reported craving for methamphetamine after stress testing showed decreases or much smaller increases compared to that for cocaine. Neither stress test significantly increased salivary cortisol or DHEA, and changes in hormone concentrations were not related to subjective responses. These results suggest that stress imagery testing procedures may be useful as provocative tests of stress-induced affect and stimulant drug craving. Although less convincing because of the heterogeneity of the subjects, they also suggest that HPA axis responsivity is not clearly linked to acute stress-induced stimulant craving or affective response.

Relationships among ventral striatal dopamine release, cortisol secretion, and subjective responses to amphetamine

There is evidence that stress and glucocorticoids alter drug self-administration and mesolimbic dopamine (DA) activity in preclinical models. The primary purpose of this study was to test the hypothesis that glucocorticoids are associated with psychostimulant reinforcement and DA release in humans. In total, 16 healthy adults, ages 18-27 years, underwent two consecutive 90-min PET studies with high specific activity [11C]raclopride. The first scan was preceded by intravenous saline, and the second by intravenous amphetamine (AMPH 0.3 mg/kg). DA release was defined as the percent change in raclopride binding between the placebo and AMPH scans. Measures of subjective drug effects, plasma cortisol, and growth hormone (GH) were obtained. Findings showed that cortisol levels were positively associated with AMPH-induced DA release in the left ventral striatum (LVS) and the dorsal putamen. Subjects with higher cortisol responses to AMPH also reported more positive subjective drug effects than subjects with lower cortisol responses; no association was observed between cortisol levels and negative drug effects. Higher ratings of positive drug effects were also associated with greater DA release in the LVS, dorsal putamen, and dorsal caudate. A general lack of relationship was observed between GH responses to AMPH and DA release or subjective drug responses. Our findings provide evidence of interrelationships between glucocorticoid levels, subjective responses to IV AMPH, and brain DA release in humans. The results are consistent with those of preclinical studies, suggesting that individual differences in HPA axis function may influence vulnerability to alcohol and drug dependence in humans.