The effects of fenfluramine on sleep and prolactin in depressed inpatients: a comparison of potential indices of brain serotonergic responsivity

The Effects of Daytime Psilocybin Administration on Sleep: Implications for Antidepressant Action

Serotonergic agonist psilocybin is a psychedelic with antidepressant potential. Sleep may interact with psilocybin’s antidepressant properties like other antidepressant drugs via induction of neuroplasticity. The main aim of the study was to evaluate the effect of psilocybin on sleep architecture on the night after psilocybin administration. Regarding the potential antidepressant properties, we hypothesized that psilocybin, similar to other classical antidepressants, would reduce rapid eye movement (REM) sleep and prolong REM sleep latency. Moreover, we also hypothesized that psilocybin would promote slow-wave activity (SWA) expression in the first sleep cycle, a marker of sleep-related neuroplasticity. Twenty healthy volunteers (10 women, age 28–53) underwent two drug administration sessions, psilocybin or placebo, in a randomized, double-blinded design. Changes in sleep macrostructure, SWA during the first sleep cycle, whole night EEG spectral power across frequencies in non-rapid eye movement (NREM) and REM sleep, and changes in subjective sleep measures were analyzed. The results revealed prolonged REM sleep latency after psilocybin administration and a trend toward a decrease in overall REM sleep duration. No changes in NREM sleep were observed. Psilocybin did not affect EEG power spectra in NREM or REM sleep when examined across the whole night. However, psilocybin suppressed SWA in the first sleep cycle. No evidence was found for sleep-related neuroplasticity, however, a different dosage, timing, effect on homeostatic regulation of sleep, or other mechanisms related to antidepressant effects may play a role. Overall, this study suggests that potential antidepressant properties of psilocybin might be related to changes in sleep.

Acute effects of 3,4-methylenedioxymethamphetamine (MDMA) and R(-) MDMA on actigraphy-based daytime activity and sleep parameters in rhesus monkeys

3,4-Methylenedioxymethamphetamine (MDMA) affects monoaminergic pathways that play a critical role in sleep-wake cycles. Dopaminergic mechanisms are thought to mediate the sleep-disrupting effects of stimulant drugs. However, the mechanisms underlying the effects of MDMA on sleep-wake cycles and the effects of R(-) MDMA, a stereoisomer that lacks dopaminergic activity, on sleep remain unknown. The aim of the present study was to investigate the effects of racemic MDMA and R(-) MDMA on daytime activity and sleep-like parameters evaluated with actigraphy in adult rhesus macaques (Macaca mulatta, n = 6). Actiwatch monitors were attached to the monkeys' collars and actigraphy recording was conducted during baseline conditions and after the administration of acute intramuscular injections of saline (vehicle), racemic MDMA (0.3, 1.0, or 1.7 mg/kg), or R(-) MDMA (0.3, 1.0, or 1.7 mg/kg) at 9 or 16 h (3 h before "lights off"). Morning treatments had no effects on sleep-like parameters. Racemic MDMA decreased general daytime activity during the first hour after injection and increased daytime activity at 3 hr posttreatment. Although afternoon administration of racemic MDMA increased sleep latency, it improved other sleep parameters, decreasing wake time after sleep onset (WASO) and increasing sleep efficiency for subjects with low baseline sleep efficiency. Afternoon treatment with R(-) MDMA improved sleep measures, increasing sleep efficiency and decreasing sleep latency and WASO, while having no effects on daytime activity. The stimulant and sleep-disrupting effects of racemic MDMA are likely mediated by dopaminergic and noradrenergic mechanisms, while serotonergic pathways appear to be involved in the sleep-promoting effects of MDMA. (PsycINFO Database Record

Fenfluramine challenge test predicts outcome in pharmacological treatment of patients with functional gastrointestinal disorder

We investigated if response to the fenfluramine challenge test could predict outcome in 47 nonpsychiatric patients with chronic functional gastrointestinal disorder (FGD) treated with mianserin, a drug closely related to mirtazepine, or placebo. Sixty milligrams of fenfluramine was given orally in the morning on nonfasting basis. Serum cortisol (COR) and prolactin (PRL) were analyzed at baseline, and after 120, 180, and 240 minutes. Patients were then randomized into a 7-week double-blind treatment trial with mianserin or placebo. Response to treatment with mianserin (76% vs.18% for placebo) was closely linked to a high increase in PRL and COR following a fenfluramine challenge test (positive predictive power=72%). Adding length of illness history increased both positive and negative predictive power to 92%. Our results indicate that the fenfluramine challenge test may be a potentially useful tool to identify nonpsychiatric subjects with FGD, who will most likely respond to treatment with a combined alpha2 and 5HT-2 and -3 antagonist.

Differential response of rapid eye movement sleep to cholinergic blockade by scopolamine in currently depressed, remitted, and normal control subjects

The degree of cholinergic dysregulation of sleep in adult depression was evaluated using scopolamine. On separate sessions, placebo and scopolamine (4.5 micrograms/kg, IM) were administered to 14 patients with unipolar major depression, 16 recovered/remitted patients, and 18 normal controls. Scopolamine increased rapid eye movement (REM) latency (RL), reduced REM activity (RA), REM density (RD), and REM duration, and increased the percentage of stage 4 sleep in all groups. There was a differential effect of scopolamine on RL, RA, and REM duration for the first REM period, and on percentage of stage 4 sleep. Whereas a primary cholinergic hyperactivity could account for the RA and RD responses, the response profile for RL was more compatible with reduced aminergic tone as the proximal cause of the cholinergic hyperactivity. Whether the sleep abnormalities observed in remitted patients reflect an underlying vulnerability for development or recurrence of depression, and/or a scar, remains to be determined.

D,L-fenfluramine challenge test: experience in nonpatient sample

The plasma prolactin response to a single-dose fenfluramine challenge is increasingly utilized in psychiatric research as an indirect and noninvasive measure of central serotonergic activity. However, the influences of age, gender, and body weight on prolactin response and characterization of physical and psychological symptoms evoked by fenfluramine remain poorly studied. In the current study, 83 nonpatient male and female volunteers, 25-60 years old, were administered a standardized fenfluramine challenge test (60 mg). Serial blood samples for plasma drug concentration and plasma prolactin concentration were obtained and side effects reported by participants were recorded. Analyses revealed that both plasma drug concentration and prolactin response were correlated with weight-relative dose (r = 0.43 and r = 0.38, respectively; p < 0.001). No significant relationship was noted between prolactin response and either age or gender. Symptoms during fenfluramine challenge were reported by 90% of subjects, most commonly fatigue, headache, lightheadedness, and difficulty concentrating. Overall side effect severity was related to weight-relative dose (r = 0.26; p < 0.05) and prolactin response (r = 0.42; p < 0.001). We conclude that fenfluramine challenge results should be reported as change in plasma prolactin relative to dose, and that in nonpatient samples the test is associated with frequent side effects.