The association between sleep and cognitive abnormalities in bipolar disorder.

BACKGROUND: Bipolar disorder (BD) is associated with attentional and processing abnormalities. Such abnormalities are also seen in healthy subjects with sleep disruption. We hypothesised cognitive abnormalities in BD patients would be worse in those with objectively verified sleep abnormalities. METHODS: Forty-six BD patients and 42 controls had comprehensive sleep/circadian rhythm assessment over 21 days alongside mood questionnaires. Cognitive function was assessed with a range of tasks including Psychomotor Vigilance Test (PVT), Attention Network Task (ANT) and Digit Symbol Substitution Test (DSST). BD participants with normal and abnormal sleep were compared with age- and sex-matched controls. RESULTS: BD patients had longer response times and made more lapses (responses >500 ms) than controls on the PVT (both p < 0.001). However, patients with normal sleep patterns did not differ from controls while those with sleep abnormalities did (p < 0.001). An identical pattern of effects were seen with the ANT response times, with the abnormality in bipolar abnormal sleepers related to the executive attentional network. Similarly, patients made fewer correct responses on the DSST compared with the controls (p < 0.001). Bipolar normal sleepers did not differ while those with abnormal sleep did (p < 0.001). All these differences were seen in bipolar abnormal sleepers who were euthymic (p < 0.01) and across the main abnormal sleep phenotypes. CONCLUSIONS: We confirm impairment in attention and processing speed in BD. Rather than sleep abnormalities exacerbating such dysfunction, the impairments were confined to bipolar abnormal sleepers, consistent with sleep disturbance being the main driver of cognitive dysfunction.

Multiple-therapy-resistant major depressive disorder: a clinically important concept.

Many novel therapeutic options for depression exist that are either not mentioned in clinical guidelines or recommended only for use in highly specialist services. The challenge faced by clinicians is when it might be appropriate to consider such 'non-standard' interventions. This analysis proposes a framework to aid this decision.Declaration of interestIn the past 3 years R.H.M.W. has received support for research, expenses to attend conferences and fees for lecturing and consultancy work (including attending advisory boards) from various pharmaceutical companies including Astra Zeneca, Cyberonics, Eli Lilly, Janssen, LivaNova, Lundbeck, MyTomorrows, Otsuka, Pfizer, Roche, Servier, SPIMACO and Sunovion. D.M.B.C. has received fees from LivaNova for attending an advisory board. In the past 3 years A.J.C. has received fees for lecturing from Astra Zeneca and Lundbeck; fees for consulting from LivaNova, Janssen and Allergan; and research grant support from Lundbeck.In the past 3 years A.C. has received fees for lecturing from pharmaceutical companies namely Lundbeck and Sunovion. In the past 3 years A.L.M. has received support for attending seminars and fees for consultancy work (including advisory board) from Medtronic Inc and LivaNova. R.M. holds joint research grants with a number of digital companies that investigate devices for depression including Alpha-stim, Big White Wall, P1vital, Intel, Johnson and Johnson and Lundbeck through his mindTech and CLAHRC EM roles. M.S. is an associate at Blueriver Consulting providing intelligence to NHS organisations, pharmaceutical and devices companies. He has received honoraria for presentations and advisory boards with Lundbeck, Eli Lilly, URGO, AstraZeneca, Phillips and Sanofi and holds shares in Johnson and Johnson. In the past 3 years P.R.A.S. has received support for research, expenses to attend conferences and fees for lecturing and consultancy work (including attending an advisory board) from life sciences companies including Corcept Therapeutics, Indivior and LivaNova. In the past 3 years P.S.T. has received consultancy fees as an advisory board member from the following companies: Galen Limited, Sunovion Pharmaceuticals Europe Ltd, myTomorrows and LivaNova. A.H.Y. has undertaken paid lectures and advisory boards for all major pharmaceutical companies with drugs used in affective and related disorders and LivaNova. He has received funding for investigator initiated studies from AstraZeneca, Eli Lilly, Lundbeck and Wyeth.

Study protocol for a randomised pragmatic trial comparing the clinical and cost effectiveness of lithium and quetiapine augmentation in treatment resistant depression (the LQD study).

BACKGROUND: Approximately 30-50% of patients with major depressive disorder can be classed as treatment resistant, widely defined as a failure to respond to two or more adequate trials of antidepressants in the current episode. Treatment resistant depression is associated with a poorer prognosis and higher mortality rates. One treatment option is to augment an existing antidepressant with a second agent. Lithium and the atypical antipsychotic quetiapine are two such add-on therapies and are currently recommended as first line options for treatment resistant depression. However, whilst neither treatment has been established as superior to the other in short-term studies, they have yet to be compared head-to-head in longer term studies, or with a superiority design in this patient group. METHODS: The Lithium versus Quetiapine in Depression (LQD) study is a parallel group, multi-centre, pragmatic, open-label, patient randomised clinical trial designed to address this gap in knowledge. The study will compare the clinical and cost effectiveness of the decision to prescribe lithium or quetiapine add-on therapy to antidepressant medication for patients with treatment resistant depression. Patients will be randomised 1:1 and followed up over 12 months, with the hypothesis being that quetiapine will be superior to lithium. The primary outcomes will be: (1) time to all-cause treatment discontinuation over one year, and (2) self-rated depression symptoms rated weekly for one year via the Quick Inventory of Depressive Symptomatology. Other outcomes will include between group differences in response and remission rates, quality of life, social functioning, cost-effectiveness and the frequency of serious adverse events and side effects. DISCUSSION: The trial aims to help shape the treatment pathway for patients with treatment resistant depression, by determining whether the decision to prescribe quetiapine is superior to lithium. Strengths of the study include its pragmatic superiority design, broad inclusion criteria (external validity) and longer follow up than previous studies. TRIAL REGISTRATION: ISRCTN registry: ISRCTN16387615 , registered 28 February 2016. ClinicalTrials.gov: NCT03004521 , registered 17 November 2016.

Altered hippocampal function in major depression despite intact structure and resting perfusion.

BACKGROUND: Hippocampal volume reductions in major depression have been frequently reported. However, evidence for functional abnormalities in the same region in depression has been less clear. We investigated hippocampal function in depression using functional magnetic resonance imaging (fMRI) and neuropsychological tasks tapping spatial memory function, with complementing measures of hippocampal volume and resting blood flow to aid interpretation. METHOD: A total of 20 patients with major depressive disorder (MDD) and a matched group of 20 healthy individuals participated. Participants underwent multimodal magnetic resonance imaging (MRI): fMRI during a spatial memory task, and structural MRI and resting blood flow measurements of the hippocampal region using arterial spin labelling. An offline battery of neuropsychological tests, including several measures of spatial memory, was also completed. RESULTS: The fMRI analysis showed significant group differences in bilateral anterior regions of the hippocampus. While control participants showed task-dependent differences in blood oxygen level-dependent (BOLD) signal, depressed patients did not. No group differences were detected with regard to hippocampal volume or resting blood flow. Patients showed reduced performance in several offline neuropsychological measures. All group differences were independent of differences in hippocampal volume and hippocampal blood flow. CONCLUSIONS: Functional abnormalities of the hippocampus can be observed in patients with MDD even when the volume and resting perfusion in the same region appear normal. This suggests that changes in hippocampal function can be observed independently of structural abnormalities of the hippocampus in depression.

The interrelationship between attentional and executive deficits in major depressive disorder.

OBJECTIVE: Cognitive dysfunction is an established feature of major depressive disorder (MDD). However, it remains unclear whether deficits in different cognitive domains are relatively independent or originate from a circumscribed 'primary deficit'. This study tested the hypothesis that a deficit in attention represents a primary deficit in depression. METHOD: Neuropsychological function was assessed in 30 depressed patients with MDD and 34 control participants. Cognitive composites were derived from a minimum of three tests and included attention, executive function, visuospatial memory and verbal memory. A multivariate analysis of variance was used to assess group differences in overall cognitive performance, and multiple regression models were used to evaluate the role of attention in deficits in other domains. RESULTS: The cognitive deficit in the depressed sample was found to be characterized by poorer performance in attention and executive function. When evaluating the interrelationship between the two deficits, the attentional deficit was found to persist when variability in executive function was statistically accounted for, whilst the executive deficit was eliminated when attention was accounted for. CONCLUSION: The results demonstrated that the attentional deficit could not be explained by deficits in executive function, which provides support for a primary attention deficit in depression.

Early life trauma, depression and the glucocorticoid receptor gene--an epigenetic perspective.

BACKGROUND: Hopes to identify genetic susceptibility loci accounting for the heritability seen in unipolar depression have not been fully realized. Family history remains the 'gold standard' for both risk stratification and prognosis in complex phenotypes such as depression. Meanwhile, the physiological mechanisms underlying life-event triggers for depression remain opaque. Epigenetics, comprising heritable changes in gene expression other than alterations of the nucleotide sequence, may offer a way to deepen our understanding of the aetiology and pathophysiology of unipolar depression and optimize treatments. A heuristic target for exploring the relevance of epigenetic changes in unipolar depression is the hypothalamic-pituitary-adrenal (HPA) axis. The glucocorticoid receptor (GR) gene (NR3C1) has been found to be susceptible to epigenetic modification, specifically DNA methylation, in the context of environmental stress such as early life trauma, which is an established risk for depression later in life. METHOD: In this paper we discuss the progress that has been made by studies that have investigated the relationship between depression, early trauma, the HPA axis and the NR3C1 gene. Difficulties with the design of these studies are also explored. RESULTS: Future efforts will need to comprehensively address epigenetic natural histories at the population, tissue, cell and gene levels. The complex interactions between the epigenome, genome and environment, as well as ongoing nosological difficulties, also pose significant challenges. CONCLUSIONS: The work that has been done so far is nevertheless encouraging and suggests potential mechanistic and biomarker roles for differential DNA methylation patterns in NR3C1 as well as novel therapeutic targets.

Neurocognitive intra-individual variability in mood disorders: effects on attentional response time distributions.

BACKGROUND: Attentional impairment is a core cognitive feature of major depressive disorder (MDD) and bipolar disorder (BD). However, little is known of the characteristics of response time (RT) distributions from attentional tasks. This is crucial to furthering our understanding of the profile and extent of cognitive intra-individual variability (IIV) in mood disorders. METHOD: A computerized sustained attention task was administered to 138 healthy controls and 158 patients with a mood disorder: 86 euthymic BD, 33 depressed BD and 39 medication-free MDD patients. Measures of IIV, including individual standard deviation (iSD) and coefficient of variation (CoV), were derived for each participant. Ex-Gaussian (and Vincentile) analyses were used to characterize the RT distributions into three components: mu and sigma (mean and standard deviation of the Gaussian portion of the distribution) and tau (the 'slow tail' of the distribution). RESULTS: Compared with healthy controls, iSD was increased significantly in all patient samples. Due to minimal changes in average RT, CoV was only increased significantly in BD depressed patients. Ex-Gaussian modelling indicated a significant increase in tau in euthymic BD [Cohen's d = 0.39, 95% confidence interval (CI) 0.09-0.69, p = 0.011], and both sigma (d = 0.57, 95% CI 0.07-1.05, p = 0.025) and tau (d = 1.14, 95% CI 0.60-1.64, p < 0.0001) in depressed BD. The mu parameter did not differ from controls. CONCLUSIONS: Increased cognitive variability may be a core feature of mood disorders. This is the first demonstration of differences in attentional RT distribution parameters between MDD and BD, and BD depression and euthymia. These data highlight the utility of applying measures of IIV to characterize neurocognitive variability and the great potential for future application.

Somatodendritic 5-hydroxytryptamine1A (5-HT1A) autoreceptor function in major depression as assessed using the shift in electroencephalographic frequency spectrum with buspirone.

BACKGROUND: Positron emission tomography and post-mortem studies of the number of somatodendritic 5-hydroxytryptamine(1A) (5-HT(1A)) autoreceptors in raphé nuclei have found both increases and decreases in depression. However, recent genetic studies suggest they may be increased in number and/or function. The current study examined the effect of buspirone on the electroencephalographic (EEG) centroid frequency, a putative index of somatodendritic 5-HT(1A) receptor functional status, in a cohort of medication-free depressed patients and controls. METHOD: A total of 15 depressed patients (nine male) and intelligence quotient (IQ)-, gender- and age-matched healthy controls had resting EEG recorded from 29 scalp electrodes prior to and 30, 60 and 90 min after oral buspirone (30 mg) administration. The effect of buspirone on somatodendritic 5-HT(1A) receptors was assessed by calculating the EEG centroid frequency between 6 and 10.5 Hz. The effect of buspirone on postsynaptic 5-HT(1A) receptors was assessed by measuring plasma growth hormone, prolactin and cortisol concentrations. RESULTS: Analysis of variance revealed a significantly greater effect of buspirone on the EEG centroid frequency in patients compared with controls (F1,28 = 6.55, p = 0.016). There was no significant difference in the neuroendocrine responses between the two groups. CONCLUSIONS: These findings are consistent with an increase in the functional status of somatodendritic, but not postsynaptic, 5-HT1A autoreceptors, in medication-free depressed patients in line with hypotheses based on genetic data. This increase in functional status would be hypothesized to lead to an increase in serotonergic negative feedback, and hence decreased release of 5-HT at raphé projection sites, in depressed patients.

Trajectories of improvement with repetitive transcranial magnetic stimulation for treatment-resistant major depression in the BRIGhTMIND trial.

Repetitive transcranial magnetic stimulation (rTMS) is an established non-invasive brain stimulation treatment for major depressive disorder, but there is marked inter-individual variability in response. Using latent class growth analysis with session-by-session patient global impression ratings from the recently completed BRIGhTMIND trial, we identified five distinct classes of improvement trajectory during a 20-session treatment course. This included a substantial class of patients noticing delayed onset of improvement. Contrary to prior expectations, members of a class characterised by early and continued improvement showed greatest inter-session variability in stimulated location. By relating target locations and inter-session variability to a well-studied atlas, we estimated an average of 3.0 brain networks were stimulated across the treatment course in this group, compared to 1.1 in a group that reported symptom worsening (p < 0.001, d = 0.893). If confirmed, this would suggest that deliberate targeting of multiple brain networks could be beneficial to rTMS outcomes.

A naturalistic evaluation and audit database of agomelatine: clinical outcome at 12 weeks.

OBJECTIVE: To determine the effectiveness of agomelatine in routine clinical practice and explore factors associated with response and continuation. METHOD: Consecutive patients prescribed agomelatine in participating psychiatric services were included. Patient demographic and outcome data were collected at treatment initiation and then at weeks 4, 8 and 12. Outcomes were analysed with respect to clinical and demographic factors. RESULTS: A total of 110 patients from nine NHS trusts were followed through 12 weeks of treatment. Agomelatine was largely used in difficult-to-treat or refractory patients: 83 (75%) had failed to respond to, or relapsed on, prior antidepressants. There were high rates of physical (54.5%) and psychiatric (50.0%) comorbidity. At 12 weeks of treatment, 68 (62%) continued agomelatine treatment. Overall, 69 subjects (62.7%) improved by at least one point of the Clinical Global Impression (severity) scale. Of 42 who discontinued, 23 (56%) discontinued because of lack of efficacy and 10 (24%) due to an adverse event. Of all variables examined, only a history of more than five episodes of depression significantly predicted discontinuation of treatment (OR continuation - 0.36, 95% CI 0.14, 0.95). CONCLUSION: Agomelatine was effective and generally well tolerated in a cohort of difficult-to-treat patients in clinical practice.

The use of antidepressants in clinical practice: focus on agomelatine.

OBJECTIVE: Agomelatine (Valdoxan) is licensed by the European Medicines Agency for the treatment of major depressive episodes in adults. The objective of this review was to consider how the drug should be used in clinical practice in particular starting, stopping and switching to and from the drug. METHODS: The existing clinical evidence was reviewed. RESULTS: Data suggest that when switching to agomelatine from other antidepressants consideration should be given to tapering the previous antidepressant in order to minimize the risk of the original drug causing discontinuation/withdrawal symptoms. The risk of pharmacological interactions between most antidepressants and agomelatine is low and so tapering the previous antidepressant can usually be done after agomelatine has been started. An exception is fluvoxamine which should not be concurrently prescribed with agomelatine. As agomelatine appears to cause no significant discontinuation symptoms, it can probably be stopped abruptly when treatment is completed or when switching to another antidepressant. CONCLUSIONS: While this guidance may change as clinical evidence and experience grows, currently agomelatine appears to have a good tolerability profile and is relatively easy to use, though prescribers should note the requirement to conduct liver function tests (LFTs) in accordance with the Summary of Product Characteristics (SPC).

The identification, assessment and management of difficult-to-treat depression: An international consensus statement.

BACKGROUND: Many depressed patients are not able to achieve or sustain symptom remission despite serial treatment trials - often termed "treatment resistant depression". A broader, perhaps more empathic concept of "difficult-to-treat depression" (DTD) was considered. METHODS: A consensus group discussed the definition, clinical recognition, assessment and management implications of the DTD heuristic. RESULTS: The group proposed that DTD be defined as "depression that continues to cause significant burden despite usual treatment efforts". All depression management should include a thorough initial assessment. When DTD is recognized, a regular reassessment that employs a multi-dimensional framework to identify addressable barriers to successful treatment (including patient-, illness- and treatment-related factors) is advised, along with specific recommendations for addressing these factors. The emphasis of treatment, in the first instance, shifts from a goal of remission to optimal symptom control, daily psychosocial functional and quality of life, based on a patient-centred approach with shared decision-making to enhance the timely consideration of all treatment options (including pharmacotherapy, psychotherapy, neurostimulation, etc.) to optimize outcomes when sustained remission is elusive. LIMITATIONS: The recommended definition and management of DTD is based largely on expert consensus. While DTD would seem to have clinical utility, its specificity and objectivity may be insufficient to define clinical populations for regulatory trial purposes, though DTD could define populations for service provision or phase 4 trials. CONCLUSIONS: DTD provides a clinically useful conceptualization that implies a search for and remediation of specific patient-, illness- and treatment obstacles to optimizing outcomes of relevance to patients.

Evidence-based guidelines for treating depressive disorders with antidepressants: a revision of the 2000 British Association for Psychopharmacology guidelines.

A revision of the 2000 British Association for Psychopharmacology evidence-based guidelines for treating depressive disorders with antidepressants was undertaken to incorporate new evidence and to update the recommendations where appropriate. A consensus meeting involving experts in depressive disorders and their management was held in May 2006. Key areas in treating depression were reviewed, and the strength of evidence and clinical implications were considered. The guidelines were drawn up after extensive feedback from participants and interested parties. A literature review is provided, which identifies the quality of evidence to inform the recommendations, the strength of which are based on the level of evidence. These guidelines cover the nature and detection of depressive disorders, acute treatment with antidepressant drugs, choice of drug versus alternative treatment, practical issues in prescribing and management, next-step treatment, relapse prevention, treatment of relapse, and stopping treatment.

Evidence-based guidelines for treating depressive disorders with antidepressants: A revision of the 2008 British Association for Psychopharmacology guidelines.

A revision of the 2008 British Association for Psychopharmacology evidence-based guidelines for treating depressive disorders with antidepressants was undertaken in order to incorporate new evidence and to update the recommendations where appropriate. A consensus meeting involving experts in depressive disorders and their management was held in September 2012. Key areas in treating depression were reviewed and the strength of evidence and clinical implications were considered. The guidelines were then revised after extensive feedback from participants and interested parties. A literature review is provided which identifies the quality of evidence upon which the recommendations are made. These guidelines cover the nature and detection of depressive disorders, acute treatment with antidepressant drugs, choice of drug versus alternative treatment, practical issues in prescribing and management, next-step treatment, relapse prevention, treatment of relapse and stopping treatment. Significant changes since the last guidelines were published in 2008 include the availability of new antidepressant treatment options, improved evidence supporting certain augmentation strategies (drug and non-drug), management of potential long-term side effects, updated guidance for prescribing in elderly and adolescent populations and updated guidance for optimal prescribing. Suggestions for future research priorities are also made.

The temperature dependence of high-threshold calcium channel currents recorded from adult rat dorsal raphe neurones.

The temperature dependence of HVA calcium channel currents, using barium as the charge carrier, was studied in acutely isolated adult rat dorsal raphe neurones. Current amplitude was found to be highly sensitive with a Q10 of between 1.7 and 2.5. The most sensitive component of current is that that is activated from hyperpolarized holding potentials, and inactivates during a 200 msec test pulse. The least sensitive is the more sustained current elicited from depolarized potentials. Increases in temperature were also found to cause an irreversible shift in the current-voltage relationship in the hyperpolarizing direction. By far the most temperature-sensitive property was the activation time constant with an extraordinary Q10 of between 10 and 12. This was not significantly affected by holding potential, though the time constant itself is dependent on the test potential. Increases in temperature to 25 degrees C or above revealed a fast inactivating component, not seen at lower temperatures. These findings suggest that there are at least three components of HVA current in dorsal raphe neurones. In addition, the remarkably high Q10 for activation kinetics suggests that the processes underlying calcium channel current activation are multifaceted and complex. The following paper puts forward a new hypothesis which attempts to explain the way in which neurotransmitters modulate the activation kinetics of HVA calcium channel currents.

The modulation of calcium channel currents recorded from adult rat dorsal raphe neurones by 5-HT1A receptor or direct G-protein activation.

The effect 5-HT1A receptor activation on the temperature dependence of HVA calcium channel currents has been studied in acutely isolated DR neurones, using barium as the charge carrier. 8-OH-DPAT caused a reduction in the temperature dependence of the peak current amplitude. However the most dramatic effect of 8-OH-DPAT was a large reduction in Q10 for the current activation rate. This also occurred with direct G-protein activation using GTP gamma S. In the presence of GTP gamma S, current activation became bi-exponential, rather than mono-exponential as in the control situation. The time constants of both components were significantly slower than the controls, and the Q10 for both components was significantly lower. GDP beta S had no effect on the temperature dependence or kinetics of activation of HVA current. Depolarizing prepulses applied prior to test pulses were able to reverse the action of 8-OH-DPAT on the Q10 of the activation rate. When prepulses were applied to cells containing GTP gamma S, the activation rate Q10 was similar to control values. We postulate that the highly significant reduction in activation rate Q10, seen with both 8-OH-DPAT and GTP gamma S, is as a result of a change in the mechanism underlying activation of HVA channels on depolarization. Contrary to previous models of calcium current modulation our results show that the mechanisms responsible for slowed activation by transmitters and facilitation of the residual current by depolarizing prepulses have little in common. We present a new model of transmitter modulation of HVA current, consistent with a mechanistic approach to channel subunit structure.

Effects of repeated cortisol administration on brain potential correlates of episodic memory retrieval.

RATIONALE: Neuropsychological impairments in depressive illness may be secondary to hypercortisolaemia. Cortisol administration to healthy subjects impairs episodic memory, though how this is mediated is unknown. OBJECTIVES: To examine the effects of 1 week's administration of cortisol on the neural correlates of episodic memory in healthy subjects. METHODS: Fourteen healthy men were treated with oral cortisol (hydrocortisone 20 mg) or placebo twice daily for 1 week, in a double blind, crossover fashion. Event related potentials (ERPs) were recorded during a well-validated source memory task. Subjects listened to words spoken in a male or female voice. At test, old and new words were presented visually; subjects judged whether words were old or new, and if old, the gender of the voice at study. RESULTS: Response times were significantly speeded by cortisol. A significant reduction in recognition accuracy with cortisol was found for the second study occasion. ERP recordings with placebo showed greater positivity over left parietal and right frontal scalp areas for ERPs to items given correct source judgements versus correctly rejected new items. In comparison, cortisol increased ERP voltage between 500 and 1400 ms post-stimulus and this effect interacted with item type and electrode site, being diffusely distributed for correct rejections but of a lesser magnitude frontally for old items accorded a correct source judgement. CONCLUSIONS: Repeated cortisol administration leads to a qualitative change in the neural correlates of episodic memory retrieval in healthy subjects. This change may contribute to cognitive impairments seen in illnesses characterised by hypercortisolaemia.

EEG effects of buspirone and pindolol: a method of examining 5-HT1A receptor function in humans.

RATIONALE: An involvement of 5-HT(1A) receptors is postulated in the pathophysiology of affective disorders and mechanism of action of antidepressants. Methods for studying their functional integrity in humans are, however, limited. Preliminary data suggests that activation of somatodendritic 5-HT(1A) receptors cause a negative shift in the EEG frequency spectrum. Animal research suggests that pindolol is an agonist at these receptors but an antagonist at postsynaptic 5-HT(1A) receptors. OBJECTIVE: We postulated that while pindolol would antagonise known postsynaptic mediated neuroendocrine responses to the 5-HT(1A) agonist buspirone, both drugs would have a similar effect on the EEG frequency spectrum. METHODS: Fourteen healthy men were administered placebo or pindolol (20 mg orally) 90 min before placebo or buspirone (30 mg orally) in a double blind cross-over study. Plasma prolactin and growth hormone were assayed and EEGs recorded before and after drug administration. RESULTS: A significant negative shift in the EEG frequency spectrum was found for both buspirone and pindolol, with the combination producing a similar effect to each drug alone. In contrast, the neuroendocrine response to buspirone was significantly attenuated by pindolol. CONCLUSIONS: The data obtained are consistent with the EEG effects of buspirone and pindolol being mediated by somatodendritic 5-HT(1A) receptors, in contrast to the neuroendocrine response, which is known to be mediated by postsynaptic receptors. The development of this novel method of assessing somatodendritic 5-HT(1A) receptors in humans is a potentially important advance which may allow the testing of hypotheses of its involvement in depression and response to antidepressants.