Neuroendocrinological investigations during sleep deprivation in depression. II. Longitudinal measurement of thyrotropin, TH, cortisol, prolactin, GH, and LH during sleep and sleep deprivation

Treatment-resistant depression: Neurobiological correlates and the effect of sleep deprivation with sleep phase advance for the augmentation of pharmacotherapy

OBJECTIVES

To assess the neurobiology of treatment-resistant depression (TRD), and factors connected with improvement after total sleep deprivation (TSD) with sleep phase advance (SPA), for the augmentation of pharmacotherapy.

METHODS

The study comprised 43 patients with TRD, (15 male, 28 female), aged 48 ± 13 years, with the illness duration 12 ± 9 years, and the depressive episode 8 ± 7 months. TRD was defined as a lack of significant improvement despite at least two antidepressant treatments and the augmentation with mood-stabilisers. Clinical improvement (response) was a reduction of ≥50% of points in the Hamilton Depression Rating Scale (HDRS), and the remission criterion was ≤7 points in HDRS, lasting until the 14th day after TSD + SPA.

RESULTS

TRD severity was associated with greater activity of the hypothalamic-pituitary-adrenal axis, the pro-inflammatory status of the immune system and lower reactivity of the hypothalamic-pituitary-thyroid axis. The response was achieved by 18 of 42 subjects, and connected with the later onset and shorter duration of the disease. In responders, there was a decrease in cortisol and interferon-gamma. In all subjects, a decrease in thyroid hormones was observed.

CONCLUSIONS

TRD can improve after augmentation of pharmacotherapy by TSD + SPA and some biological changes may be compatible with a decrease in allostatic load.

Acute sleep deprivation leads to growth hormone (GH) resistance in rats

Sleep is an essential physiological process that is required by all higher animals. Sleep has many important physiological functions. Previous studies have focused on the relationship between sleep and growth hormone secretion patterns. However, to date, whether sleep affects the biological activities of GH remains unclear. Here, we investigated this issue by evaluating the growth hormone receptor (GHR)-mediated intracellular signalling pathway in a sleep-deprived rat model. The results showed that GH's signalling ability is decreased in an acute sleep deprivation rat model. JAK2-STAT signalling was decreased significantly compared to that in control rats. We further analysed the possible molecular mechanism of GH signal inhibition in sleep-deprived rats. The results showed that the protein expression levels of SOCS3 (suppressors of cytokine signalling 3, which functions as the negative regulatory molecule of GH's signalling) increased; however, other negative regulatory proteins, such as protein phosphatase (PTP1B), did not change. In addition, acute sleep deprivation results in a significant increase in serum FFA (free fatty acid) level, which is also one of the factors contributing to GH inhibition. These findings suggest that GH signal resistance may be caused by a combination of factors. This study could serve as an important reference for related studies on the effect of sleep deprivation on endocrine systems.

Perspectives in affective disorders: Clocks and sleep

Mood disorders are often characterised by alterations in circadian rhythms, sleep disturbances and seasonal exacerbation. Conversely, chronobiological treatments utilise zeitgebers for circadian rhythms such as light to improve mood and stabilise sleep, and manipulations of sleep timing and duration as rapid antidepressant modalities. Although sleep deprivation ("wake therapy") can act within hours, and its mood-elevating effects be maintained by regular morning light administration/medication/earlier sleep, it has not entered the regular guidelines for treating affective disorders as a first-line treatment. The hindrances to using chronotherapeutics may lie in their lack of patentability, few sponsors to carry out large multi-centre trials, non-reimbursement by medical insurance and their perceived difficulty or exotic "alternative" nature. Future use can be promoted by new technology (single-sample phase measurements, phone apps, movement and sleep trackers) that provides ambulatory documentation over long periods and feedback to therapist and patient. Light combinations with cognitive behavioural therapy and sleep hygiene practice may speed up and also maintain response. The urgent need for new antidepressants should hopefully lead to reconsideration and implementation of these non-pharmacological methods, as well as further clinical trials. We review the putative neurochemical mechanisms underlying the antidepressant effect of sleep deprivation and light therapy, and current knowledge linking clocks and sleep with affective disorders: neurotransmitter switching, stress and cortico-limbic reactivity, clock genes, cortical neuroplasticity, connectomics and neuroinflammation. Despite the complexity of multi-system mechanisms, more insight will lead to fine tuning and better application of circadian and sleep-related treatments of depression.

Determinants of prolactin in postmenopausal Chinese women in Singapore

PURPOSE

Mechanistic and observational data together support a role for prolactin in breast cancer development. Determinants of prolactin in Asian populations have not been meaningfully explored, despite the lower risk of breast cancer in Asian populations.

METHODS

Determinants of plasma prolactin were evaluated in 442 postmenopausal women enrolled in the Singapore Chinese Health Study, a population-based prospective cohort study. At baseline all cohort members completed an in-person interview that elicited information on diet, menstrual and reproductive history, and lifestyle factors. One year after cohort initiation we began collecting blood samples. Quantified were plasma concentrations of prolactin, estrone, estradiol, testosterone, androstenedione, and sex hormone-binding globulin (SHBG). Analysis of covariance method was used for statistical analyses with age at blood draw, time since last meal, and time at blood draw as covariates.

RESULTS

Mean prolactin levels were 25.1% lower with older age at menarche (p value = 0.001), and 27.6% higher with greater years between menarche and menopause (p value = 0.009). Prolactin levels were also positively associated with increased sleep duration (p value = 0.005). The independent determinants of prolactin were years from menarche to menopause, hours of sleep, and the plasma hormones estrone and SHBG (all p values < 0.01).

CONCLUSION

The role of prolactin in breast cancer development may involve reproductive and lifestyle factors, such as a longer duration of menstrual cycling and sleep patterns.

Sleep deprivation therapy for depression

Sleep deprivation (SD) is the most widely documented rapid-onset antidepressant therapy, targeting the broadly defined depressive syndrome. Although SD responses are transient, its effects can be sustained by concomitant medications (e.g., selective serotonin reuptake inhibitors and lithium) and circadian-related interventions (e.g., bright light and sleep phase advance). Thus, considering its safety, this technique can now be considered among the first-line antidepressant treatment strategies for patients affected by mood disorders. SD is a complex intervention and it should be considered multi-target in nature. Thus, the mechanisms explaining its antidepressant effect can be looked for on many levels, involving not only monoaminergic mechanisms but also sleep homeostatic and circadian mechanisms, glutamatergic mechanisms and synaptic plasticity.

Mood and metabolic consequences of sleep deprivation as a potential endophenotype' in bipolar disorder

It has been commonly recognized that circadian rhythm and sleep/wake cycle are causally involved in bipolar disorder. There has been a paucity of systematic research considering the relations between sleep and mood states in bipolar disorder. The current study examines the possible influences of sleep deprivation on mood states and endocrine functions among first-degree relatives of patients with bipolar disorder and healthy controls. Blood samples were taken at two time points in the consecutive mornings at predeprivation and postdeprivation periods. Participants simultaneously completed the Profiles of Mood States at two time points after giving blood samples. Plasma T3 and TSH levels increased after total sleep deprivation in both groups. Sleep deprivation induced TSH levels were reversely associated with depression-dejection among healthy controls. A paradoxical effect was detected for only the first-degree relatives of the patients that changes in plasma cortisol levels negatively linked to depression-dejection and anger-hostility scores after total sleep deprivation. Plasma DHEA levels became correlated with vigor-activity scores after sleep deprivation among first-degree relatives of bipolar patients. On the contrary, significant associations of depression-dejection, anger-hostility, and confusion-bewilderment with the baseline plasma DHEA levels became statistically trivial in the postdeprivation period. Findings suggested that first-degree relatives of patients with bipolar disorder had completely distinct characteristics with respect to sleep deprivation induced responses in terms of associations between endocrine functions and mood states as compared to individuals whose relatives had no psychiatric problems. Considering the relationships between endocrine functions and mood states among relatives of the patients, it appears like sleep deprivation changes the receptor sensitivity which probably plays a pivotal role on mood outcomes among the first-degree relatives of patients with bipolar disorder.

Antidepressant chronotherapeutics for bipolar depression

Chronotherapeutics refers to treatments based on the principles of circadian rhythm organization and sleep physiology, which control the exposure to environmental stimuli that act on biological rhythms, in order to achieve therapeutic effects in the treatment of psychiatric conditions. It includes manipulations of the sleep-wake cycle such as sleep deprivation and sleep phase advance, and controlled exposure to light and dark. The antidepressant effects of chronotherapeutics are evident in difficult-to-treat conditions such as bipolar depression, which has been associated with extremely low success rates of antidepressant drugs in naturalistic settings and with stable antidepressant response to chronotherapeutics in more than half of the patients. Recent advances in the study of the effects of chronotherapeutics on neurotransmitter systems, and on the biological clock machinery, allow us to pinpoint its mechanism of action and to transform it from a neglected or “orphan” treatment to a powerful clinical instrument in everyday psychiatric practice.

Post-exposure sleep deprivation facilitates correctly timed interactions between glucocorticoid and adrenergic systems, which attenuate traumatic stress responses

Reliable evidence supports the role of sleep in learning and memory processes. In rodents, sleep deprivation (SD) negatively affects consolidation of hippocampus-dependent memories. As memory is integral to post-traumatic stress symptoms, the effects of post-exposure SD on various aspect of the response to stress in a controlled, prospective animal model of post-traumatic stress disorder (PTSD) were evaluated. Rats were deprived of sleep for 6 h throughout the first resting phase after predator scent stress exposure. Behaviors in the elevated plus-maze and acoustic startle response tests were assessed 7 days later, and served for classification into behavioral response groups. Freezing response to a trauma reminder was assessed on day 8. Urine samples were collected daily for corticosterone levels, and heart rate (HR) was also measured. Finally, the impact of manipulating the hypothalamus-pituitary-adrenal axis and adrenergic activity before SD was assessed. Mifepristone (MIFE) and epinephrine (EPI) were administered systemically 10-min post-stress exposure and behavioral responses and response to trauma reminder were measured on days 7-8. Hippocampal expression of glucocorticoid receptors (GRs) and morphological assessment of arborization and dendritic spines were subsequently evaluated. Post-exposure SD effectively ameliorated long-term, stress-induced, PTSD-like behavioral disruptions, reduced trauma reminder freezing responses, and decreased hippocampal expression of GR compared with exposed-untreated controls. Although urine corticosterone levels were significantly elevated 1 h after SD and the HR was attenuated, antagonizing GRs with MIFE or stimulation of adrenergic activity with EPI effectively abolished the effect of SD. MIFE- and EPI-treated animals clearly demonstrated significantly lower total dendritic length, fewer branches and lower spine density along dentate gyrus dendrites with increased levels of GR expression 8 days after exposure, as compared with exposed-SD animals. Intentional prevention of sleep in the early aftermath of stress exposure may well be beneficial in attenuating traumatic stress-related sequelae. Post-exposure SD may disrupt the consolidation of aversive or fearful memories by facilitating correctly timed interactions between glucocorticoid and adrenergic systems.

Age-dependent and -independent associations between depression, anxiety, DHEAS, and cortisol: from the MIPH Industrial Cohort Studies (MICS)

There is a well-established link between dysphoric mood and endocrine dysregulation, but the strength of this association may vary with age. In order to investigate this possibility we assessed anxiety and depression with overnight urinary cortisol and plasma dehydroepiandrosterone-sulphate (DHEAS) in 608 factory employees ranging between 21 and 62 years. As expected, DHEAS declined with age (r=-0.54, P<0.001) while there was a modest age-related increase in nocturnal cortisol (r=0.17, P<0.001). Depressive symptoms were associated with higher nocturnal cortisol (β=0.19, P<0.001), independent of age. While the association between anxiety and cortisol (age by anxiety interaction: β=0.11, P<0.05) became stronger with age, there was a similar decline in the DHEAS/cortisol ratio in high-anxious middle-aged adults (β=-0.10, P=0.018). The current findings suggest that dysphoric mood, and in particular anxiety, may exacerbate the effects of aging on cortisol release. Prospective studies are needed to determine the causal relations between dysphoric mood, cortisol and DHEAS across the lifespan.

Influence of paradoxical sleep deprivation and sleep recovery on testosterone level in rats of different ages

This study was performed to assess serum testosterone alterations induced by paradoxical sleep deprivation (PSD) and to verify their attenuation during sleep recovery (SR) based on different durations and ages. Wistar male rats aged 12 weeks for the younger group and 20 weeks for the elder group were randomly distributed into one of the following groups: a control group (cage and platform), 3-day SD, 5-day SD, 7-day SD, 1-day SR, 3-day SR and 5-day SR groups. For PSD, the modified multiple platform method was used to specifically limit rapid eye movement (REM) sleep. Differences in the testosterone and luteinizing hormone levels between the younger group and the elder group according to duration of PSD and SR recovery were analysed. Testosterone continued to fall during the sleep deprivation period in a time-dependent manner in both the younger (P=0.001, correlation coefficient r=-0.651) and elder groups (P=0.001, correlation coefficient r=-0.840). The elder group showed a significantly lower level of testosterone compared with the younger group after PSD. Upon SR after 3 days of PSD, the testosterone level continued to rise for 5 days after sleep recovery in the younger group (P=0.013), whereas testosterone concentrations failed to recover until day 5 in the elder group. PSD caused a more detrimental effect on serum testosterone in the elder group compared to the younger group with respect to decreases in luteinizing hormone (LH) levels. The replenishment of serum testosterone level was prohibited in the elder group suggesting that the effects of SD/SR may be age-dependent. The mechanism by which SD affects serum testosterone and how age may modify the process are still unclear.

Parkinson's disease as a neuroendocrine disorder of circadian function: dopamine-melatonin imbalance and the visual system in the genesis and progression of the degenerative process

For more than 50 years, Parkinson's disease (PD) has been conceptualized as a product of nigro-striatal dopamine (NSD) system degeneration. In spite of a growing body of evidence depicting the mammalian brain as an interrelated complexity of circuitous systems, dopamine (DA) deficiency of the NSD is still regarded as the main problem, with DA replacement being the purpose of therapeutic intervention. For at least 191 years circadian involvement in various aspects of PD, including depression and insomnia, has been recognized as an integral part of the symptom matrix of PD and yet attempts to elucidate the involvement of this system is uncharted territory. The present review attempts a major reorganization of mammalian brain into a coordinated complex involving the NSD and the retinal hypothalamic tract (RHT) as the primary systems involved in the retino-diencephalic/mesencephalic-pineal (RDMP) axis. Secondary systems including the lateral hypothalamus (LH), the area postraema (AP) and the subthalamic nucleus (STN) also form an integral part of this system as they have been shown to be either intimately related to the primary systems of the RDMP axis or have been shown to be significantly involved in the expression and treatment of PD. A large volume of evidence suggests that the RDMP axis is activated during the course of PD and during therapeutic intervention. Four types of neurotoxicity associated with melatonin are identified and the susceptibility of various parts of the RDMP axis to undergo neuropathological change, the tendency for melatonin to induce PD-like behavioural toxicity, and the relationship of this to PD symptomotology are described. This includes adverse effects of melatonin on motor function, hypotension, the adjuvant use of benzodiazepines, depression, insomnia, body weight regulation and various biochemical effects of melatonin administration: all problems currently facing the proposal to introduce melatonin as an adjuvant. It is suggested further that traditional DA replacement may well work by exerting its effect upon the circadian system, rather than simply replacing deficient DA. Activation of the circadian function by antagonizing melatonin with bright light not only has therapeutic value in treating the primary symptoms of PD but it shares a common mechanism with L-dopa in reducing the occurrence of seborrheic dermatitis. Concepts at the centre of understanding pineal function in PD, including pineal calcification, melatonin deficiency, symptomatic versus protective features of melatonin and antioxidative effects, are explained in a counterintuitive context. Intriguing propositions including the role of the retina in the aetiology of PD and that the nigra functions as a retina in this disorder are presented with the intention to provide a new understanding of the underlying compromised function in PD and to provide new treatment strategies. For the first time, abundant evidence is presented describing PD as an endocrine disorder of melatonin hyperplasia. The role of circadian interventive therapies and internal desynchrony in the aetiology and progression of PD provides a new direction for understanding the underlying physiology of a disease which is currently in a state of impasse and provides new hope for those who suffer from its debilitating effects.

Chronotherapeutics in a psychiatric ward

Psychiatric chronotherapeutics is the controlled exposure to environmental stimuli that act on biological rhythms in order to achieve therapeutic effects in the treatment of psychiatric conditions. In recent years some techniques (mainly light therapy and sleep deprivation) have passed the experimental developmental phase and reached the status of powerful and affordable clinical interventions for everyday clinical treatment of depressed patients. These techniques target the same brain neurotransmitter systems and the same brain areas as do antidepressant drugs, and should be administered under careful medical supervision. Their effects are rapid and transient, but can be stabilised by combining techniques among themselves or together with common drug treatments. Antidepressant chronotherapeutics target the broadly defined depressive syndrome, with response and relapse rates similar to those obtained with antidepressant drugs, and good results are obtained even in difficult-to-treat conditions such as bipolar depression. Chronotherapeutics offer a benign alternative to more radical treatments of depression for the treatment of severe depression in psychiatric wards, but with the advantage of rapidity of onset.

Distinctions between bipolar and unipolar depression

This is a review of the studies comparing unipolar and bipolar depression, with focus on the course, symptomatology, neurobiology, and psychosocial literatures. These are reviewed with one question in mind: does the evidence support diagnosing bipolar and unipolar depressions as the same disorder or different? The current nomenclature of bipolar and unipolar disorders has resulted in research that compares these disorders as a whole, without considering depression separately from mania within bipolar disorder. Future research should investigate two broad categories of depression and mania as separate disease processes that are highly comorbid.

Daily variations in type II iodothyronine deiodinase activity in the rat brain as controlled by the biological clock

Type II deiodinase (D2) plays a key role in regulating thyroid hormone-dependent processes in, among others, the central nervous system (CNS) by accelerating the intracellular conversion of T4 into active T3. Just like the well-known daily rhythm of the hormones of the hypothalamo-pituitary-thyroid axis, D2 activity also appears to show daily variations. However, the mechanisms involved in generating these daily variations, especially in the CNS, are not known. Therefore, we decided to investigate the role the master biological clock, located in the hypothalamus, plays with respect to D2 activity in the rat CNS as well as the role of one of its main hormonal outputs, i.e. plasma corticosterone. D2 activity showed a significant daily rhythm in the pineal and pituitary gland as well as hypothalamic and cortical brain tissue, albeit with a different timing of its acrophase in the different tissues. Ablation of the biological clock abolished the daily variations of D2 activity in all four tissues studied. The main effect of the knockout of the suprachiasmatic nuclei (SCN) was a reduction of nocturnal peak levels in D2 activity. Moreover, contrary to previous observations in SCN-intact animals, in SCN-lesioned animals, the decreased levels of D2 activity are accompanied by decreased plasma levels of the thyroid hormones, suggesting that the SCN separately stimulates D2 activity as well as the hypothalamo-pituitary-thyroid axis.

Dopamine receptor D2 and D3 gene variants are not associated with the antidepressant effect of total sleep deprivation in bipolar depression

Total sleep deprivation (TSD) is an effective treatment for mood disorders that is thought to act through an enhancement in several neurotransmitter pathways including dopaminergic transmission. Genetic factors are likely to play a major role in determining individual differences in TSD response. The aim of this study is to investigate the influence of dopamine receptor D3 (DRD3) and dopamine receptor D2 (DRD2) variants on TSD antidepressant efficacy in bipolar disorder. One hundred twenty-four depressed inpatients affected by bipolar disorder (DSM-IV) were treated with TSD and were genotyped for DRD3 first exon Gly/Ser variants and DRD2 codon 311 Ser/Cys variants using polymerase chain reaction techniques. DRD3 and DRD2 variants were not associated with TSD outcome. Consideration of possible stratification effects such as gender, age at onset and duration of illness did not reveal any association either. The tested gene variants are not a main factor influencing TSD outcome in bipolar disorder.

Blunted prolactin response to fentanyl in depression. Normalizing effect of partial sleep deprivation

There is some evidence that sleep deprivation (SD) might exert its antidepressant properties by involving endogenous opioid mechanisms. The authors investigated the effects of mu-receptor agonist administration on prolactin release in depressed patients before and after partial SD. Medication-free female depressed inpatients (N=18) were participating in two fentanyl challenge tests after partial SD and undisturbed sleep, 3 days apart in random order. Healthy volunteer women (N=10) were enrolled after full night sleep as comparison subjects. Five of them had placebo trials. Participants were given an intravenous injection of 0.1 mg/70 kg fentanyl at 9:00 AM. The prolactin secretory response to the opiate agonist was investigated for 1 h with serial blood sampling. After a night of undisturbed sleep, fentanyl administration prompted increases in plasma prolactin concentrations with blunted responses found in the depressed group. Following partial SD, the stimulated prolactin secretion of depressed patients increased significantly and was comparable to the response of comparison subjects. These findings suggest that SD acts via an opioid/dopamine-related mechanism. An alternative explanation, based on serotonin involvement is addressed in the discussion.

Potential mechanisms of the sleep therapies for depression

Sleep deprivation for one night has been investigated as a treatment for depression since the first publications describing its antidepressant properties almost 30 years ago [Pflug and Tolle, 1971: Int Pharmacopsychiatry 6:187-196]. It remains a field of active research. It is the only intervention consistently demonstrated to produce next-day antidepressant results. This makes sleep deprivation an exciting and unique tool to study the pathophysiology of depressive disorders and to formulate targets for novel antidepressant agents. Importantly, it is also an effective, but underused, clinical treatment for unipolar and bipolar depression.

Dopaminergic augmentation of sleep deprivation effects in bipolar depression

Total sleep deprivation (TSD) has been used in association with lithium salts and with serotonergic and noradrenergic antidepressants, leading to sustained improvements in patients affected by major depression. Current theories on the neurobiological mechanism of action of TSD propose a major role for enhanced dopamine activity. To test the clinical relevance of dopaminergic enhancement in TSD, we treated a homogeneous sample of 28 bipolar depressed patients with three cycles of TSD combined with placebo or with the dopaminergic antidepressant amineptine. Changes in mood over time were rated with self-administered visual analogue scales and with the Montgomery-Asberg Depression Rating Scale. Patients showed improved mean daily-mood scores after TSD, an effect that was highest at the first cycle and decreased with treatment repetition. Amineptine enhanced the effects of TSD on perceived mood during the first two TSD cycles, but patients in the placebo and amineptine groups showed comparable results at the end of the treatment. Despite its theoretical importance, the clinical usefulness of combining TSD with a dopaminergic agent must be questioned.

Antidepressive response to sleep deprivation in unipolar depression is not associated with dopamine D3 receptor genotype

The psychostimulant theory of antidepressive sleep deprivation (SD) proposes a contribution of dopamine D3 receptors (DRD3) in the limbic system to the antidepressant effects of SD. Neuroendocrinological studies suggest a positive correlation of clinical response to SD and cortisol secretion. We hypothesized that the clinical response to SD and amount of cortisol secretion upon SD is associated with the 1-1 genotype of the Bal1 polymorphism of DRD3 on exon 1. In this study, aiming at evaluating the feasibility of screening large patient samples, 52 inpatients (19 males/33 females) with unipolar depression and a score of 18 or more on the 21-item Hamilton Depression Rating Scale were treated with 1 night of total SD. We found that 31% of our patients responded to SD. There was no association between response to SD and the genotype of the DRD3 Bal1 polymorphism (p < 0.879). There was also no association between increase in cortisol secretion after SD and DRD3 genotypes (p < 1.000) in a subgroup of patients. Statistical power analysis ruled out a major effect of the DRD3 Bal1 polymorphism on clinical response to SD. These results suggest that the DRD3 Bal1 polymorphism is not a promising lead to be followed up in larger patient samples.

Sleep deprivation and hypothalamic-pituitary-adrenal (HPA) axis activity in depressed patients

In the present study we investigated HPA axis activity in depressed patients treated with partial sleep deprivation (PSD) in order to identify endocrinological characteristics related to PSD responsiveness. Thirty-three drug-free patients (14 men, 19 women) suffering from major depression according to DSM-IV criteria were treated with PSD. Response to PSD was defined as a reduction of at least 30% according to the 6-item version of the Hamilton Depression Scale (6-HAMD). Subsequently, the combined dexamethasone-suppression/CRH-stimulation test (DEX/CRH test) was performed. Patients were pretreated with 1.5 mg dexamethasone (DEX) at 23:00 h and challenged with 100 microg corticotropin-releasing hormone (CRH) the following day. Postdexamethasone cortisol concentrations (before CRH administration) served as parameters for the DST status (dexamethasone suppression test). The cortisol stimulation after CRH was used as measurement for the DEX/CRH test status. Of the depressive patients, 54.5% (18 out of 33) responded to PSD. DST suppressors (postdexamethasone cortisol levels < 15 ng/ml) showed a significantly greater reduction in 6-HAMD scores after PSD than DST nonsuppressors. Furthermore, a significant negative correlation between postdexamethasone cortisol levels and reduction in 6-HAMD scores after PSD could be established. However, there was no relationship between the cortisol stimulation following CRH challenge and response to PSD. Although the combined DEX/CRH challenge test is a more sensitive marker for HPA axis dysregulation in depression than the standard DST, the negative feedback of the HPA system reflected by the DST status is apparently more closely associated with response to partial sleep deprivation in major depressive disorder.

Hypothalamo-pituitary-adrenal axis activity is related to the level of central arousal: effect of sleep deprivation on the association of high-frequency waking electroencephalogram with cortisol release

The temporal and quantitative interrelationships between the hypothalamo-pituitary-adrenal (HPA) axis activity and the level of central arousal were studied in 10 healthy young men during daytime wakefulness. Two experimental sessions were conducted randomly between 09.00 and 18.00 h, once after nocturnal sleep and once after a night of total sleep deprivation. Spectral analysis of serial waking electroencephalography (EEG) from a short target fixation task repeated every 10 min was undertaken, along with an estimation of cortisol secretory profiles by deconvolution of plasma radioimmunoassay measures obtained from continuous blood withdrawal with regular sampling at a 10-min interval. Following nocturnal sleep, a temporal association between the HPA axis activity and the waking EEG activity was found, cortisol secretory rate following changes in frontal gamma (20-45 Hz) band power by 10 min (average R = 0.458, p < 0.001). Although it remained significant (average R = 0.276, p < 0.05), the association strength decreased significantly following total sleep deprivation (p < 0.05, Wilcoxon test). Cortisol plasma level, secretory rate and pulse amplitude were increased as well as waking EEG power in the delta (0.5-5.5 Hz), theta (5.5-8.5 Hz) and gamma frequency bands (all p values <0.05, Student t tests). The sleep deprivation-related increases in cortisol secretory rate and waking EEG gamma activity were quantitatively associated (R = 0.504, p < 0.05). These results support the existence of a common ultradian regulatory mechanism, co-ordinating HPA axis activity to the level of central arousal in man, which seems involved in the sleep deprivation-induced hyper-arousal.

Myocardial infarction during sleep deprivation in a patient with dextrocardia--a case report

A patient with dextrocardia who suffered his first myocardial infarction after approximately 26 hours of a diagnostic sleep deprivation protocol is described. The infarction started about 3 hours after a significant improvement in mood, which persisted during and after infarction. Total sleep deprivation may be an acute risk factor for myocardial infarction.

Cortisol circadian rhythms during the menstrual cycle and with sleep deprivation in premenstrual dysphoric disorder and normal control subjects

BACKGROUND

In this study we extended previous work by examining whether disturbances in the circadian rhythms of cortisol during the menstrual cycle distinguish patients with premenstrual dysphoric disorder (PMDD) from normal control (NC) subjects. In addition, we tested the differential response to the effects of early and late partial sleep deprivation on cortisol rhythms.

METHODS

In 15 PMDD and 15 NC subjects we measured cortisol levels every 30 min from 6:00 PM to 9:00 AM during midfollicular (MF) and late luteal (LL) menstrual cycle phases and also during a randomized crossover trial of early (sleep 3:00 AM-7:00 AM) versus late (sleep 9:00 PM-1:00 AM) partial sleep deprivation administered in two subsequent and separate luteal phases.

RESULTS

In follicular versus luteal menstrual cycle phases we observed altered timing but not quantitative measures of cortisol secretion in PMDD subjects, compared with NC subjects: in the LL versus MF phase the cortisol acrophase was a mean of 1 hour earlier in NC subjects, but not in PMDD subjects. The effect of sleep deprivation on cortisol timing measures also differed for PMDD versus NC subjects: during late partial sleep deprivation (when subjects' sleep was earlier), the cortisol acrophase was almost 2 hours earlier in PMDD subjects.

CONCLUSIONS

Timing rather than quantitative measures of cortisol secretion differentiated PMDD subjects from NC subjects both during the menstrual cycle and in response to early versus late sleep deprivation interventions.

Thyroid function and response to 48-hour sleep deprivation in treatment-resistant depressed patients

BACKGROUND

Clinical depression is associated with abnormalities of the hypothalamic-pituitary-thyroid axis. Changes in thyroid function during sleep deprivation may be related to its antidepressant effects.

METHODS

Levels of thyroid-stimulating hormone, tri-iodothyronine, tri-iodothyronine uptake, thyroxine, and free thyroxine were measured before, during, and after a 48-hour sleep deprivation in nine treatment-resistant depressed patients. Clinical state was assessed every 4 hours. A retrospective study of 26 similar patients was added for cross-validation.

RESULTS

Significant increases in thyroid-stimulating hormone and tri-iodothyronine during sleep deprivation were not correlated with clinical improvement. Sleep deprivation responders had lower tri-iodothyronine uptake levels than nonresponders in both the prospective (p <.02) and the retrospective (p <.03) samples.

CONCLUSIONS

The lower tri-iodothyronine uptake values in responders may identify a subgroup of depressed patients who respond to sleep deprivation by virtue of some abnormality of the hypothalamic-pituitary-thyroid axis that is temporarily corrected by sleep deprivation.

Dopamine receptor D4 is not associated with antidepressant activity of sleep deprivation

Total sleep deprivation (TSD) is an effective treatment for mood disorders which is thought to act through an enhancement in several neurotransmitter pathways including dopaminergic transmission. However, not all patients respond to TSD and genetic factors are likely to play a major role in determining TSD response. The aim of this study is to investigate the influence of dopamine receptor D4 exon 3 (DRD4) variants on TSD antidepressant efficacy in bipolar disorder. One hundred and twenty-four depressed inpatients affected by bipolar disorder (DSM-IV) were treated with repeated cycles of TSD and were typed for DRD4 variants at the third exon using polymerase chain reaction (PCR) techniques. DRD4 variants were not associated with TSD outcome. Consideration of possible stratification effects such as gender, age at onset and duration of illness did not reveal any association either. DRD4 exon 3 variants are not a main factor influencing TSD outcome in bipolar disorder.

Sleep deprivation therapy in depressive illness and Parkinson's disease

1. Sleep deprivation is commonly associated with feelings of fatigue and cognitive impairment. 2. Patients with depressive illness, however, often experience mood improvements under these same conditions. 3. Other studies now show that tremor and rigidity, in patients with Parkinson's disease, are also improved by sleep depression therapy. 4. The neural substrates which underlie these effects are unclear. Some recent evidence, however, suggests that sleep deprivation may activate mechanisms which are otherwise typical of conditions of metabolic stress. 5. A common feature of these mechanisms is the suppression of cholinergic activity which is thought to be excessive, in relation to monoamine transmission, in both depression and Parkinson's disease.

Reversal of diurnal cortisol rhythm and suppression of plasma testosterone in obstetric residents on call

OBJECTIVE

The study was undertaken to quantify the psychologic and physiologic responses to the stresses of an obstetrics/gynecology residency program.

METHODS

Six male residents were studied on four occasions: one day during the first 2 weeks of their residency, one day immediately following a vacation period, one day after a night on call in obstetrics, and one day while in the gynecology clinic. Stress was evaluated by validated psychologic instruments and by levels of plasma testosterone, luteinizing hormone (LH), cortisol, and prolactin in morning and afternoon blood samples.

RESULTS

Self-reported stress was significantly elevated during the first 2 weeks of the residency after a night on call. Anxiety scores were significantly elevated after a night on call as were depression subscores for some residents. Plasma testosterone was highly significantly suppressed after the obstetrics night on call and during the first 2 weeks of the residency in comparison with the vacation period. Luteinizing hormone levels were also significantly lower after the obstetrics on-call experience. Plasma cortisol levels after a night on call were suppressed in the morning and normal or elevated in the afternoon. In comparison, the gynecology rotation was associated with normal levels of testosterone and lower levels of cortisol.

CONCLUSION

In this small sample of residents, we observed an inverse relationship between self-reported stress levels and the concentrations of plasma testosterone and LH. The high levels of stress and anxiety expressed after a night on call also disrupted the normal pattern of plasma cortisol levels.

The unipolar-bipolar dichotomy and the response to sleep deprivation

Fifty-one inpatients affected by a major depressive episode were divided into four groups according to mood disorder diagnosis and previous clinical history (bipolar disorder type I; bipolar disorder type II; major depressive disorder with at least three previous depressive episodes; and single depressive episode patients) and administered three consecutive total sleep deprivation (TSD) cycles. Mood changes were rated with a reduced version of the Hamilton Depression Rating Scale and with self-administered visual analogue scales. TSD caused better clinical effects in bipolar and single-episode patients; in particular, unipolar patients lacked effects in perceived mood after the first TSD and showed worse Hamilton ratings in respect to the other groups after the three TSD treatments. Discriminant function analysis could correctly classify 80% of bipolar patients, post hoc, based on TSD response. Further researches on the clinical efficacy of TSD must take into account the heterogeneity of depression and of its biological substrate.

Relationships between thyroid hormone and antidepressant responses to total sleep deprivation in mood disorder patients

BACKGROUND

Acute transient antidepressant effects of sleep deprivation are consistently observed in 50% of depressed patients, but the mechanisms of these, at times, dramatic improvements in mood have not been adequately elucidated. Some, but not all, studies suggest a relationship to increased thyroid-stimulating hormone (TSH) secretion.

METHODS

TSH and other thyroid indices were measured at 8:00 AM after a baseline night's sleep and at 8:00 AM following a night of total sleep deprivation (S.D.) in 34 medication-free, affective disorder patients assessed with Hamilton, Beck, and Bunney-Hamburg depression ratings as well as two hourly self-ratings on a visual analog scale.

RESULTS

Compared with baseline, S.D. induced highly significant increases in TSH, levothyroxine, free levothyroxine, and triiodothyronine. The 12 S.D. responders tended to have greater TSH increases than the 15 nonresponders (p < .10). The change in Beck depression ratings significantly correlated with the change in TSH (r = -.40, p = .0496, n = 24).

CONCLUSIONS

These data are consistent with several other reports of a significant relationship between degree of antidepressant response to S.D. and increases in TSH measured at 8:00 AM near their usual nadir. Acute removal of the sleep-related break on the hypothalamic-pituitary-thyroid axis remains a promising candidate for the mechanism of sleep deprivation-induced improvement in mood in depressed patients.

Sleep deprivation hastens the antidepressant action of fluoxetine

Among ten bipolar depressed patients admitted to our psychiatric ward, five patients were treated with fluoxetine alone and five subjects were treated with fluoxetine in association with total sleep deprivation (TSD) in order to evaluate the effect of the interaction between the administration of the serotonergic antidepressant compound fluoxetine and repeated cycles of TSD. Patients treated with fluoxetine plus repeated TSD showed a faster amelioration of depressive symptomatology compared with the other group. We discuss our findings hypothesizing an enhancement in dopaminergic and possibly in serotonergic transmission due to repeated TSD adding to the increase in serotonergic transmission due to fluoxetine medication.

Dopamine agonist amineptine prevents the antidepressant effect of sleep deprivation

In a double-blind study, the effects of the interaction between the administration of amineptine versus placebo and repeated cycles of total sleep deprivation (TSD), which is thought to act through an enhancement in dopaminergic transmission, were analyzed. Twenty-two consecutively admitted patients with bipolar depression formed the study group. Repeated administrations of TSD significantly enhanced perceived mood levels in placebo-treated patients, while amineptine administration blocked the antidepressant action of TSD. Hypothesized changes in brain dopaminergic transmission attributable to amineptine pretreatment are discussed.

Serum prolactin, growth hormone, total corticoids, thyroid hormones and thyrotropine during serial therapeutic sleep deprivation

In 13 patients fulfilling DSM-III-R criteria for a major depressive episode, hormone serum levels were measured at 8 AM on the day before and on the first and second days after partial sleep deprivation (PSD) late in the night during a 4-week course of therapy with amitriptyline in combination with 6 PSDs. Prolactin, human growth hormone (HGH) and total corticoids were not influenced by PSD. In contrast, T3 and thyrotropine (TSH) were elevated significantly on the 1st day after PSD throughout the series, but T4 less regularly. Although TSH reverted regularly to baseline values on the 2nd day after PSD, i.e. after a full night's sleep, T3 remained elevated. The hormones under discussion do not predict the therapeutic PSD effect. Nor can any correlation be determined between endocrine and clinical changes on the 1st or 2nd day after PSD. In connection with findings from sleep deprivation research in animals and in healthy subjects, the results suggest that thyroid changes under PSD may be nonspecific and unrelated to antidepressive PSD effects.

The hypothalamic-pituitary-thyroid axis in patients maintained on lithium prophylaxis for years: high triiodothyronine serum concentrations are correlated to the prophylactic efficacy

Serum concentrations of thyrotropine (TSH), thyroxine (T4), free T4 (fT4), triiodothyronine (T3) and reverse T3 (rT3) were measured 4 x during a 12-month period in 28 patients with major depressive disorder maintained on lithium prophylaxis for 4-23 years (mean = 11.8). The course of illness was carefully monitored and documented for all patients throughout a 3.5-year period. All hormones were also measured in 41 healthy controls matched for age and gender. Patients on lithium had normal serum concentrations of TSH, T4, fT4 and T3 only the levels of rT3 were elevated. The efficacy of the lithium prophylaxis was significantly correlated to the serum concentrations of T3, i.e., the higher the patients' serum levels of T3, the shorter was the overall duration of recurrences of depression within the 3.5-year period. We conclude that: (1) thyrotropine and the thyroid hormones, which are often abnormal during the first weeks or months of lithium treatment, returned to normal when lithium prophylaxis was maintained for years; (2) a possible explanation for the higher T3-serum concentrations in responders might be that lithium interacts with thyroid hormone metabolism in the CNS, leading to enhanced T3 concentrations in the tissue and to a secondary increase in the serum concentrations of T3.

The effect of sleep deprivation on motor impairment and retinal adaptation in Parkinson's disease

1. Sleep deprivation has previously been reported to result in a temporary improvement of motor deficits in Parkinson's disease patients. 2. The mechanism of this action is unclear but may involve an activation of dopamine pathways. 3. Other studies suggest that light adaptive changes in the retinal pigment epithelium may serve as a model of dopamine sensitivity. 4. The present study examined the effects of one night of total sleep deprivation on RPE potentials and motor abnormalities in Parkinson's patients. 5. Sleep deprivation significantly improved motor deficits and these changes were strongly correlated with increases in light adaptive RPE potentials.

Influence of thyroid hormones on morning and evening TSH response to TRH in major depression

The serum levels of thyroid hormones and thyrotropin (TSH) were evaluated before and after 8 PM and 11 PM thyrotropin-releasing hormone (TRH) challenges, on the same day, in 41 drug-free DSM-III-R euthyroid major depressed inpatients and 16 hospitalized controls. Depressed patients exhibited elevated circulating concentrations of thyroid hormones, which were associated with and may have contributed to the blunted TSH response to TRH. This was confirmed by: (a) higher basal levels (albeit not always statistically significant) of free triiodothyronine (FT3B) and free thyroxine (FT4B) at 8 AM and 11 PM in the depressed patient population compared with the controls; (b) lower basal levels of TSH in the depressed subjects (even though this was only statistically significant at the 11 PM sampling) compared with the controls; (c) blunted TSH response to TRH (delta TSH) in the depressed group (although this was only statistically significant at 11 PM) and blunted delta delta TSH values (differences between 11 PM-delta TSH and 8 AM-delta TSH).

The influence of sleep deprivation on thyroid hormone metabolism in rat frontal cortex

The effects of 24 h sleep deprivation (SD) on central thyroid hormone metabolism were investigated in rat frontal cortex. SD induced a significant rise in the activity of iodothyronine type II 5'-deiodinase (5'D-II), which catalyzes the conversion of thyroxine (T4) to triiodothyronine (T3) in the rat central nervous system (CNS). Tissue concentrations of T4 remained unchanged, whereas levels of T3 increased to more than 150% of the corresponding levels measured in control rats. Serum concentrations of T4 and T3 were also significantly enhanced by SD--an effect that has previously been described in depressed patients having undergone the same procedure. These results suggest that SD can dramatically increase T3 concentrations (and possibly function) in rat CNS. Whether or not these findings are of relevance in regard to the well-known antidepressant effect of SD in psychiatric patients with major depressive disorders remains to be established.

Influence of partial sleep deprivation on the secretion of thyrotropin, thyroid hormones, growth hormone, prolactin, luteinizing hormone, follicle stimulating hormone, and estradiol in healthy young women

The influence of partial sleep deprivation during the second half of the night on the secretion of thyroid stimulating hormone (TSH), thyroxin (T4), free T4 (fT4), triiodothyronine (T3), prolactin (PRL), growth hormone (GH), luteinizing hormone (LH), follicle stimulating hormone (FSH), and estradiol (E2) was investigated in 10 healthy young women. Blood samples were drawn at hourly intervals over a 64-hour period (i.e., 3 consecutive days and nights). During night 2, all subjects were awakened at 1:30 a.m. During partial sleep deprivation, TSH concentrations increased significantly and remained elevated throughout the following day. Levels of T4, fT4, and T3 were enhanced during the partial sleep deprivation hours only, and changes in these hormones seemed to be independent of TSH. PRL levels decreased, LH and E2 concentrations increased, and GH and FSH secretion remained unchanged during partial sleep deprivation. This pattern of change of different endocrine axes during partial sleep deprivation resembles those seen after total sleep deprivation, suggesting that similar neurochemical changes are induced by both forms of antidepressant therapy. The late evening GH peak occurred almost exclusively before the onset of sleep. Partial sleep deprivation did not influence the chronobiological profiles of any of the hormones investigated. The chemical changes underlying these alterations are speculated to involve enhancement of central norepinephrine and dopamine activity with a concomitant increase in the activity of the sympathetic nervous system.

The influence of total sleep deprivation on urinary excretion of catecholamine metabolites in major depression

To elucidate the influence of total sleep deprivation (TSD) on catecholaminergic neurotransmission, which is assumed to be disturbed in depression, 9 depressive patients collected consecutive 24-h urine samples prior to (baseline), during (TSD) and following total sleep deprivation (post-TSD). Urine samples were analysed for total MHPG (3-methoxy-4-hydroxyphenylglycol), conjugates of MHPG (glucuronide and sulfate), excretion of HVA (homovanillic acid) and VMA (3-methoxy-4-hydroxymandelic acid). TSD increased the urinary excretion of MHPG-sulfate as a marker of the central norepinephrine metabolism and the excretion rates of VMA and HVA as indices of the peripheral catecholamine metabolism. Patients with higher VMA values prior to TSD reacted worse, and the VMA increase due to TSD was positively correlated with the response. The results demonstrate that TSD, besides acting as a stimulus on the peripheral sympathetic nervous system, influences central nervous noradrenergic neurotransmission, as reflected by the increase of MHPG-sulfate.

Sleep deprivation in depressed adolescents and psychiatric controls

Up to 70% of depressed adults have an antidepressant response to sleep deprivation. To study the effects of sleep deprivation on depression severity and level of arousal in psychiatrically disturbed adolescents, we deprived 17 patients of sleep for 36 hours. Severity of depression and subjective arousal were assessed at baseline, during sleep deprivation, and after 1 night's recovery sleep. We found that severely depressed adolescents showed a significant decrease in depression severity, whereas depressed patients in remission and psychiatric controls worsened after sleep deprivation. Patients with depression in remission showed a significant decrease in subjective arousal after sleep deprivation. In contrast to findings in depressed adults, the effects of sleep deprivation persisted after 1 night of recovery sleep, and diurnal variation of mood did not predict response to sleep deprivation. These findings are consistent with those reported in the adult literature, and suggest a common psychophysiology between adult and adolescent depression.

Nocturnal prolactin pulses in relation to luteinizing hormone and thyrotropin

The two hypothalamic releasing factors, luteinizing hormone releasing hormone (LHRH) and thyrotropin releasing hormone (TRH), have been shown to stimulate pituitary prolactin (PRL) release as well as their respective pituitary hormones, luteinizing hormone (LH) and thyrotropin (TSH). In this study the influence of LH and TSH regulatory mechanisms on nocturnal PRL secretion was investigated by evaluating whether the coincidence of PRL with LH and TSH pulses occurred more frequently than would be expected if the hormone generators were not coupled. Thirty night studies were conducted in twelve healthy male subjects. Six subjects underwent 3 studies and 6 subjects 2 studies. Blood was collected into aliquots at 10 min intervals throughout the night and plasma concentrations of PRL, TSH, and LH were determined. From the plasma profiles, hormone secretory rates were calculated using a method of deconvolution. Significant plasma and secretory hormone pulses were identified by a peak detection computer program. For statistical analysis the night studies of each subject were concatenated. Concomitance between the plasma pulses of both TSH and LH with PRL was insufficient to reject the null hypothesis of random coincidence. An increase in the number of subjects demonstrating significant coincidence between the hormone pulses was obtained when secretory pulses were analysed. Seven of the 12 and 10 of the 12 subjects showed significant concomitance between PRL and respectively TSH and LH. This proportion was sufficient to confirm copulsatility between PRL and LH. These results suggest that LH regulatory mechanisms are involved in the generation of the nocturnal pulsatile PRL profile, TRH may also play a role in the secretion of PRL at a central level, but was not reflected in the plasma or secretory profiles because of other overriding regulatory factors.

Nocturnal plasma thyrotropin variations are related to slow-wave sleep

The thyrotropin (TSH) nycthemeral pattern is known to be strongly influenced by sleep, but previous studies have failed to demonstrate any link between sleep structure and TSH variations. Using 10-min blood sampling, nocturnal TSH profiles were analysed in 24 young healthy subjects during normal sleep. Six of the subjects then underwent a partial sleep deprivation experiment, sleep was permitted from 03.00 hours to 07.00 hours. Descending slopes of TSH values were observed for the first 20 minutes of SWS episodes, whereas no significant trend was found for other sleep stages. During the period of sleep deprivation, nocturnal TSH levels increased and then declined immediately after sleep onset; however, the association between SWS and descending TSH slopes persisted. This temporal concordance suggests that some particular mechanisms associated with SWS may modulate TSH release, or conversely that increasing TSH levels prevent the occurrence of SWS.

Sleep deprivation therapy

This review reports, with as much detail as possible, on the literature relating to therapeutic sleep deprivation (or induced-wakefulness therapy) since it was first described in 1971. The antidepressive effect of sleep deprivation has been substantiated by numerous studies. A series of clinical predictors of response to sleep deprivation are also described. Partial sleep deprivation late in the night is equivalent to total sleep deprivation in terms of therapeutic value and--because of its simpler application--can be regarded today as the sleep deprivation method of choice. The status of sleep deprivation in the overall treatment schedule for depressive disorders is discussed in detail. Numerous findings, some of them contradictory, have been published on the effect of sleep deprivation on biological variables. To date, no unequivocal explanation has been found for the mechanism of action of sleep deprivation.

The influence of physical activity and posture on the antidepressant effect of sleep deprivation in depressed patients

A possible role of the factors 'physical activity' and 'posture' in the antidepressant effect of a total night's sleep deprivation (TSD) was investigated in 30 patients with major depressive disorder. Fifteen patients underwent TSD under 'conventional' conditions, while the other 15 were kept in bed during TSD but were not permitted to sleep. There was no significant difference between the antidepressant effects of TSD in the two groups. This result suggests that it is wakefulness itself rather than changes in physical activity or posture that is involved in the mechanism of the antidepressant action of TSD.

Thyrotropin (TSH) and thyroid hormone concentrations during partial sleep deprivation in patients with major depressive disorder

Thyrotropin (TSH), thyroxine (T4), free T4, triiodothyronine (T3), and free T3 (fT3) concentrations were measured in 25 patients with major depressive disorder at 8 a.m. both before and after partial sleep deprivation (PSD) during the second half of the night. Significant increases in TSH and T3 levels and a corresponding trend in fT3 levels were seen. No convincing correlations occurred between changes in the secretion of any of the hormones and the antidepressant effect of PSD. However, this does not rule out the possibility that the two phenomena, which occur in depression at different anatomical levels with presumably different degrees of disturbance in the respective receptor systems, have common underlying neurochemical mechanisms. Comparison of the effect of the PSD on changes in hormone secretion and mood with the corresponding effects in a sample of depressed patients who underwent total sleep deprivation showed no significant differences between the effects of these two forms of sleep deprivation on either variable.

Thyrotropin and prolactin responses to protirelin (TRH) prior to and during chronic imipramine treatment in patients with panic disorder

The effects of protirelin [thyrotropin-releasing hormone (TRH)] administration on the release of thyrotropin (TSH) and prolactin (PRL) were examined in 14 patients with panic disorder prior to and during chronic treatment with imipramine. During imipramine treatment, the patients exhibited an increase in their TSH response to TRH (delta delta max TSH = 3.65 +/- 6.02 mu IU/ml, p less than 0.05) and in their PRL response to TRH (delta AUCPRL = 734 +/- 965 ng/ml/45 min, p less than 0.005). Several behavioral measures correlated with the neuroendocrine measures during imipramine therapy. These preliminary findings might suggest a role for changes in dopaminergic function in the clinical effects of imipramine in patients with panic disorder.