EEG profiles of fenfluramine, amobarbital and dextroamphetamine in normal volunteers

The effects of dexamphetamine on the resting-state electroencephalogram and functional connectivity

The catecholamines-dopamine and noradrenaline-play important roles in directing and guiding behavior. Disorders of these systems, particularly within the dopamine system, are associated with several severe and chronically disabling psychiatric and neurological disorders. We used the recently published group independent components analysis (ICA) procedure outlined by Chen et al. (2013) to present the first pharmaco-EEG ICA analysis of the resting-state EEG in healthy participants administered 0.45 mg/kg dexamphetamine. Twenty-eight healthy participants between 18 and 41 were recruited. Bayesian nested-domain models that explicitly account for spatial and functional relationships were used to contrast placebo and dexamphetamine on component spectral power and several connectivity metrics. Dexamphetamine led to reductions across delta, theta, and alpha spectral power bands that were predominantly localized to Frontal and Central regions. Beta 1 and beta 2 power were reduced by dexamphetamine at Frontal ICs, while beta 2 and gamma power was enhanced by dexamphetamine in posterior regions, including the parietal, occipital-temporal, and occipital regions. Power-power coupling under dexamphetamine was similar for both states, resembling the eyes open condition under placebo. However, orthogonalized measures of power coupling and phase coupling did not show the same effect of dexamphetamine as power-power coupling. We discuss the alterations of low- and high-frequency EEG power in response to dexamphetamine within the context of disorders of dopamine regulation, in particular schizophrenia, as well as in the context of a recently hypothesized association between low-frequency power and aspects of anhedonia. Hum Brain Mapp 37:570-588, 2016. © 2015 Wiley Periodicals, Inc.

Localization of MDMA-induced brain activity in healthy volunteers using low resolution brain electromagnetic tomography (LORETA)

3,4-Methylenedioxymethamphetamine (MDMA; 'Ecstasy') is a psychostimulant drug producing heightened mood and facilitated social communication. In animal studies, MDMA effects are primarily mediated by serotonin (5-HT), but also by dopamine (DA) and possibly noradrenaline (NA). In humans, however, the neurochemical and neurophysiological basis of acute MDMA effects remains unknown. The distribution of active neuronal populations after administration of a single dose of MDMA (1.7 mg/kg) or placebo was studied in 16 healthy, MDMA-naïve volunteers. Thirty-one-channel scalp EEGs during resting with open and closed eyes was analyzed in the different EEG frequency bands. Scalp maps of power showed significant, global differences between MDMA and placebo in both eye conditions and all frequency bands. Low resolution brain electromagnetic tomography (LORETA) was used to compute 3D, functional images of electric neuronal activity from the scalp EEG data. MDMA produced a widespread decrease of slow and medium frequency activity and an increase of fast frequency activity in the anterior temporal and posterior orbital cortex, concomitant with a marked enhancement of mood, emotional arousal and increased extraversion. This activation of frontotemporal areas indicates that the observed enhancement of mood and possibly the increased extroversion rely on modulation of limbic orbitofrontal and anterotemporal structures known to be involved in emotional processes. Comparison of the MDMA-specific EEG pattern with that of various 5-HT, DA, and NA agonists indicates that serotonin, noradrenaline, and, to a lesser degree, dopamine, contribute to the effects of MDMA on EEG, and possibly also on mood and behavior.

The effect of acute tryptophan depletion and fenfluramine on quantitative EEG and mood in healthy male subjects

BACKGROUND

Efforts to model putative serotonergic deficits associated with affective disorders have frequently involved acute tryptophan depletion (ATD) as a manipulation strategy aimed at lowering brain serotonin synthesis. In an attempt to widen the scope of the measurement probes used in these investigations, the central actions of ATD and a subsequent dose of fenfluramine were examined via utilization of quantitative electroencephalography (EEG) and mood ratings.

METHODS

Electroencephalograms (EEG) and subjective mood ratings were assessed in 28 healthy men before and after double-blind ingestion of a tryptophan-depleting (T-) amino acid mixture, or a nutritionally balanced (B) amino acid mixture containing tryptophan, and again after a single-blind oral dose of D,L-fenfluramine hydrochloride (60 mg).

RESULTS

Compared to the B mixture, the T- mixture reduced total plasma tryptophan by more than 75% 5 hours after ingestion. Tryptophan depletion was associated with a modest lowering of mood and a slowing of EEG as indicated by increases in delta amplitude. Fenfluramine caused no change in mood but increased fast wave (beta) activity in anterior recordings when administered after the T-, but not after the B mixture.

CONCLUSIONS

Quantitative EEG measurements may be a promising method for studying the central mechanisms underlying serotonin-mediated changes in mood and behavior.

Methylphenidate effects on EEG, behavior, and performance in boys with ADHD

The psychophysiologic and behavioral effects of methylphenidate were assessed in boys with attention deficit hyperactivity disorder between the ages of 9 and 11 years. The effects of methylphenidate on the EEG during baseline and cognitive tasks were evaluated using spectral analysis. Both subjective (rating scales) and objective (continuous performance) measures were administered and analyzed in conjunction with the electrophysiologic data. Although methylphenidate induced regional changes in the EEG under certain task-specific conditions, it had no global effects. Behavioral and performance measures improved with methylphenidate.

A close look at fenfluramine and dexfenfluramine

In an effort to combat obesity, several medications have been developed. The nonamphetamine anorectics, such as phentermine, fenfluramine, and dexfenfluramine, have been recommended as first-line drug therapy for the treatment of obesity once diet and exercise alone have failed. Numerous studies have shown that these agents can promote weight loss when combined with diet restriction and exercise. Although fenfluramine and dexfenfluramine lack the abuse potential of amphetamine and its congeners, these agents are associated with drug interactions and adverse effects. Concomitant administration of fenfluramine or dexfenfluramine with medications that enhance serotonin levels (e.g., antidepressants, monoamine oxidase inhibitors, and migraine medications) can precipitate serotonin syndrome. Sudden discontinuation of fenfluramine or dexfenfluramine after prolonged administration can precipitate withdrawal depressive symptoms. Primary pulmonary hypertension, a potentially fatal disorder, has been reported to occur approximately 30 times more frequently in patients receiving anorectic agents for more than 3 months compared to the general population. More recently, the association of these popular anorectics with valvular heart disease has caused increased concerns about their use. The risks of primary pulmonary hypertension, valvular heart disease, and the occurrence of convulsions, coma, and death in overdose appear to be equally likely with dexfenfluramine and fenfluramine. In addition, many patients who lose weight while taking these anorectics rapidly regain it after the medication has been discontinued.

The pharmacologic approach to the treatment of obesity

Obesity is a major risk factor for morbidity and mortality, and a series of pharmacologic approaches are available for helping to manage the problem. Obesity is caused by an imbalance between caloric intake and energy expenditure, which is influenced by both environmental and genetic factors. Pharmacologic treatments include anorexigenic agents, which fall into two broad categories: those that act via brain catecholamine pathways and those that act via serotonin pathways. The most recent oral agents approved are dexfenfluramine, which is currently being marketed, and sibutramine. Both agents inhibit the control reuptake of serotonin but in addition may have effects on thermogenesis. Under investigation are agents that increase energy expenditure: the beta 3-adrenergic receptor agonists and drugs that prevent the intestinal absorption of free fatty acids and cholesterol. In development are innovative approaches to influence leptin and its receptors, various obesity genes, and biologic substances thought to influence satiety (neuropeptide Y, enterostatin, cholecystokinin, bombesin, and amylin). Obesity has now become a major target for drug development not only for affecting obesity per se but also for managing and preventing comorbid conditions such as diabetes and cardiovascular disease.

Comparison of methods for the assessment of central nervous system stimulant response after dextroamphetamine administration to healthy male volunteers

The objective of this investigation was to evaluate a series of potential pharmacodynamic measures of central nervous system stimulation, including quantitative electroencephalography (EEG) and neuroendocrine, mood, and psychomotor performance measures. The reproducibility and sensitivity of the measures were compared. The study was conducted in two parts. The first part investigated the interindividual and intraindividual variability associated with a series of potential pharmacologic response measures under baseline (i.e., drug-free) conditions. It was an open-label, three-period pilot study in which healthy male volunteers underwent a series of tests (EEG, a visual continuous performance task, a finger tapping task, and self-rated mood scales) repeatedly during each study period. The second part evaluated the sensitivity of a series of potential response measures to detect the effects of dextroamphetamine, and was a double-blind, placebo-controlled, four-period crossover study in nine healthy male volunteers. Subjects received 5 mg, 10 mg, or 20 mg of dextroamphetamine or placebo orally and underwent the same series of tests as in Part I in addition to blood collection for determination of serum prolactin and dextroamphetamine levels. Peripheral response to dextroamphetamine was assessed by heart rate and blood pressure measurement. The greatest variability among days, within days, and among participants was associated with the quantitative electroencephalographic parameters studied. First-session effects were apparent for several of the tests, including EEG. Consistent response on EEG (increased alpha power) to dextroamphetamine was observed only in the three subjects who had a baseline alpha activity greater than 35%. Serum prolactin levels were inversely associated with the amount of dextroamphetamine administered, with the largest decrease in serum prolactin levels observed after the 5-mg dose, and this finding was statistically significant. Mood scales showed that three of nine participants experienced dysphoria after at least one dose level of dextroamphetamine. The effect on mood was generally greater as the dose increased. Doses could not be distinguished based on the results of the performance tests. Serum prolactin concentration was the most sensitive measure of central nervous system stimulation on EEG produced by dextroamphetamine under these study conditions. Cardiovascular measures were more sensitive measures of dextroamphetamine effects than the central nervous system measures.

Effect of dexfenfluramine on sleep in healthy subjects

The acute effects of dexfenfluramine on nocturnal sleep were studied in ten healthy male subjects by means of sleep EEG recordings and ratings of subjective sleep quality. Four different dosages (3 mg, 7 mg, 15 mg, and 30 mg) were tested, administered over a period of 3 days each. Under 15 mg and 30 mg dexfenfluramine, only slight effects on sleep were observed: 15 mg led to decreased sleep efficiency in the first night of medication, and to reduced percentage of slow wave sleep in the first and third night. A significant lengthening of REM latency was present in the third night under 30 mg dexfenfluramine, without changes in other REM sleep parameters. Daily doses of 3 mg and 7 mg dexfenfluramine did not influence sleep, except for a significant REM latency reduction observed in the first night under 3 mg. Apart from a transient slight impairment under 30 mg, ratings of subjective sleep quality did not mirror any impact of dexfenfluramine. The data suggest that therapeutic dosages of dexfenfluramine only slightly influence nocturnal sleep, which contrasts with the known impact of other anti-obesity agents like the amphetamines. Unlike classical antidepressants, dexfenfluramine does not reduce REM sleep; in light of a hypothetical link between REM sleep reduction and antidepressant action of a drug, dexfenfluramine is not expected to have a pronounced antidepressant effect.

Fenfluramine stimulation of serum cortisol in patients with major affective disorders and healthy controls: further evidence for a central serotonergic action of lithium in man

In order to investigate the influence of lithium long-term medication on serotonergic neurotransmission, fenfluramine stimulation (FFS) was used for the assessment of hormonal effects under serotonergic control. The cortisol plasma concentration following FFS was examined between 8 a.m. and 1 p.m. in 11 manic-depressive subjects under lithium prophylaxis and in 8 untreated euthymic patients. In addition, 11 healthy subjects with FFS, and 12 other subjects without FFS were investigated. The basal cortisol concentrations show considerable variation. Those of the lithium patients were in general found lower than those of the control groups. In both, the controls and the manic-depressive patients without lithium medication, no gross deviation from the expected physiological decline of morning cortisol values was found. A subtle effect of FFS in healthy subjects could be observed. In the lithium patients, however, a significant inversion of the cortisol secretion pattern with a steep increase between 10 and 12 a.m. could be demonstrated. It is concluded that FFS and lithium long-term medication exert an agonistic influence onto central serotonergic neurotransmission. Pharmacological challenge with fenfluramine may prove to be a useful tool for the investigation of serotonergic mechanisms in biological psychiatry.

Fenfluramine: amphetamine congener that fails to maintain drug-taking behavior in the rhesus monkey

Fenfluramine, over a dose range from 0.003 to 3 milligrams per kilogram of body weight, failed to maintain self-injection behavior in rhesus monkeys that had initiated and maintained responding for cocaine or methohexital. This absence of a positive reinforcing effect could not be attributed to a slow onset of drug effect or to the use of behaviorally inactive doses. Fenfluramine, because of its distinctive properties, may produce fewer problems of human abuse than do amphetamine-type agents.