The GH response to clonidine in endogenous as compared with reactive depression

From menarche to menopause: exploring the underlying biology of depression in women experiencing hormonal changes

Epidemiologic data consistently report an elevated prevalence of major depressive disorder (MDD) in women. This increase begins during adolescence and continues through the menopausal transition. Population-based clinical studies report an increase in the incidence of MDD during perimenopause compared to either the premenopausal or postmenopausal period. Evidence suggests that fluctuations and decline of hormonal levels are correlated with this observed increase in risk for MDD. A strong predictor of depression in the perimenopausal period is a previous history of MDD. However, recent studies revealed an increased risk of new onset depression in perimenopausal women without a history of MDD. Additionally, recent reports have indicated that the presence of vasomotor symptoms may be associated with an increased the risk for MDD. The objective of this paper is to review evidence that would support our hypothesis that neurotransmitter systems are affected by changes in hormonal status over the course of a woman's life, leading to increase vulnerability to perimenopausal depression. Relevant data from nonclinical experiments will be discussed in the context of observed clinical evidence of the risk for MDD before, during, and after the menopausal transition. A testable hypothesis will be proposed to advance our understanding of hormonal effects on mood.

G protein-coupled receptors in major psychiatric disorders

Although the molecular mechanisms underlying psychiatric illnesses such as depression, bipolar disorder and schizophrenia remain incompletely understood, there is increasing clinical, pharmacologic, and genetic evidence that G protein-coupled receptors (GPCRs) play critical roles in these disorders and their treatments. This perspectives paper reviews and synthesizes the available data. Dysfunction of multiple neurotransmitter and neuropeptide GPCRs in frontal cortex and limbic-related regions, such as the hippocampus, hypothalamus and brainstem, likely underlies the complex clinical picture that includes cognitive, perceptual, affective and motoric symptoms. The future development of novel agents targeting GPCR signaling cascades remains an exciting prospect for patients refractory to existing therapeutics.

Endocrine disturbances in depression

Depression is one of the most common psychiatric disorders. For a long time, clinicians suspected a causal link between depression and the endocrine system. The most frequently occurring endocrine abnormality in depressed subjects is hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. CRH and AVP are likely to play a substantial role in the pathophysiology of this disorder, and their receptors appear to be a specific target for future antidepressant drugs. Depression also affects the hypothalamic-pituitary-GH (HPGH) and -thyroid (HPT) axes. Alterations in the reproductive system may also play a role in the pathology of depression. In addition, there is increasing evidence that leptin and neurosteroids, such as DHEA, are implicated in mood disorders.

Anxious and depressive disorders and their comorbidity: effect on central nervous system noradrenergic function

BACKGROUND

Although comorbidity of anxiety with depression is common, investigations of physiologic abnormalities related specifically to comorbidity are rare. This study examined relationships of DSM-IV-defined depression, anxiety, and their comorbidity to noradrenergic function measured by blunting of the growth hormone (GH) response to the alpha2 adrenoreceptor agonist (and imidazoline receptor agent) clonidine and by blood pressure and symptom responses.

METHODS

Fifteen subjects with pure social anxiety or panic disorder, 15 with pure major depression, and 18 with both depression and anxiety were compared with healthy control subjects matched for age and gender. Other factors known to affect GH (weight, menstrual status, prior antidepressant, or other drug exposure) were controlled.

RESULTS

Anxiety produced GH blunting, but depression was associated with normal GH responses. The comorbid state did not affect results beyond the impact of anxiety. Preclonidine stress-related GH elevations were observed, to the greatest degree in anxious subjects. Relevant symptom, but not blood pressure, changes were significantly associated with blunting.

CONCLUSIONS

With use of pure depression and anxiety groups and careful control of other factors known to affect GH, these results demonstrate central nervous system noradrenergic dysfunction in anxiety disorders. In contrast to less rigorously controlled studies, noradrenergic function in depression was normal.

Evidence for alterations in α2-adrenergic receptor sensitivity in rats exposed to repeated cocaine administration

It is well established that cocaine stimulates monoamine transmission by blocking reuptake of norepinephrine (NE), dopamine and serotonin into nerve cells, yet few investigations have addressed the effects of chronic cocaine on NE function. In the present study, we examined the effects of repeated cocaine injections on neuroendocrine responses evoked by the alpha2-adrenergic receptor agonist, clonidine. Previous findings show that clonidine increases pituitary growth hormone (GH) secretion by a central mechanism involving postsynaptic alpha2-adrenergic receptors. Male rats previously fitted with indwelling jugular catheters received two daily injections of cocaine (15 mg/kg, i.p.) or saline for 7 days. At 42 h and 8 days after treatment, rats were challenged with clonidine (25 microg/kg, i.v.) or saline, and serial blood samples were withdrawn. Plasma GH and corticosterone levels were measured by radioimmunoassay. Prior cocaine exposure did not affect basal levels of either hormone. However, cocaine-pretreated rats displayed a significant reduction in clonidine-evoked GH secretion at 42 h, and this blunted response was still apparent 8 days later. Corticosterone responses produced by clonidine were similar regardless of pretreatment. The present data suggest that withdrawal from repeated cocaine injections may be accompanied by desensitization of postsynaptic alpha2-adrenoreceptors coupled to GH secretion. Since human patients with depression often exhibit blunted GH responses to clonidine, our findings provide evidence that cocaine withdrawal might produce depressive-like symptoms via dysregulation of NE mechanisms.

The effects of reboxetine, a noradrenaline reuptake inhibitor, on the plasma noradrenaline response to a cold pressor test in healthy volunteers

Previous studies have shown peripheral abnormalities in noradrenergic activity in depressed melancholic patients. These abnormalities have a relationship with short-term and long-term outcome. Little is known about the effects of antidepressant treatment on these peripheral measures such as plasma noradrenaline (NA) and the plasma NA response to a laboratory stressor, the cold pressor test (CPT). The present study examines the effects of the antidepressant reboxetine, a noradrenaline reuptake inhibitor, on baseline plasma NA and the plasma NA response to a CPT, in nine healthy volunteers compared to placebo. A double-blind crossover design was used, with each agent given for 4 weeks with a 4-week washout period. There was no effect of reboxetine on baseline plasma NA. The plasma NA response to reboxetine, with a CPT, was blunted 3 days after commencing treatment. Reboxetine alters the plasma NA response to a CPT independent of baseline plasma NA.

Birth weight and the risk of depressive disorder in late life

BACKGROUND

Low birth weight is a risk factor for coronary heart disease, diabetes, stroke and hypertension. Depression is highly associated with these conditions.

AIMS

To examine the association between birth weight and depression in late life.

METHOD

A total of 882 singleton term births in the 1920s had contemporary records of birth weight and weight at 1 year. At 68 years all completed the Geriatric Depression Scale and 867 completed the Geriatric Mental State Examination. A logistic regression was used to analyse the associations between depression, birth weight and weight at 1 year while adjusting for known risk factors.

RESULTS

Current social class, social class at birth, recent bereavement, social isolation and physical illness increased the risk of depression. After adjusting for these and weight at 1 year, the odds ratios for depression among men, but not women, rose incrementally with decreasing birth weight (1.0, 12.8; for continuous variable, P<0.007).

CONCLUSIONS

Foetal undernutrition predisposes men to depression in late adult life. If replicated, these results would suggest a neurodevelopmental aetiology of depression, possibly mediated by programming of the hypothalamic-pituitary-adrenal axis.

Noradrenergic dysfunction and antidepressant treatment response

The purpose of this study was to investigate differences in outcome following treatment with two different antidepressants in depressed patients according to their pretreatment hormonal response to clonidine. In all, 62 drug-free DSM-IV recurrent major depressed patients and 20 normal controls were studied. Patients were subsequently treated for 4 weeks with fluoxetine (n=28), or amitriptyline (n=34), and were then classified as responders or nonresponders according to their final Hamilton depression scale score. Compared to controls, depressed patients showed lower GH response to CLO (DeltaGH) (P<0.0002). One control (5%) and 35 depressed patients (56%) had blunted DeltaGH values. The efficacy of the two antidepressants was not significantly different: 15 patients responded to AMI (44%), seven patients responded to FLUOX (25%) (P>0.15). However, in the subgroup of patients with blunted DeltaGH levels, the rate of responders was higher for AMI (11/21) compared to FLUOX (1/14) treated patients (P<0.01). These results suggest that in depressed patients a blunted GH response to CLO could predict antidepressant response.

Plasma noradrenaline response to a cognitive stressor in subtypes of depressive illness

Noradrenergic function has been shown to be disrupted in depressive illness. The plasma noradrenaline response to a cognitive stressor (the Stroop test) was used to investigate noradenergic activity in subtypes of depressive illness. A Stroop test was carried out, under standardised conditions, on patients with melancholic or psychotic depression, non-melancholic depression, general anxiety disorder and normal controls. Blood samples were taken during testing for measurement of plasma noradrenaline. Although there was a trend for the plasma noradrenergic response to be reduced in the melancholic/psychotic depressed patients compared to all other groups, this did not reach statistical significance. No other inter-group comparisons were statistically significant. The plasma noradrenaline response to a cognitive stressor does not discriminate subtypes of depressive illness from normal controls. Copyright 2000 John Wiley & Sons, Ltd.

Plasma norepinephrine response to a cold pressor test in subtypes of depressive illness

Noradrenergic systems have been shown to be disordered in depressive illness. The plasma norepinephrine response to a cold pressor test was used to investigate norepinephrine activity in subtypes of depressive illness. Patients with melancholic or psychotic depression, non-melancholic depression, general anxiety disorder and normal control subjects had a cold pressor test carried out under standard conditions. Blood samples were taken to measure plasma norepinephrine during the test. The plasma norepinephrine response to a cold pressor test was reduced in the melancholic/psychotic depressed patients compared to control subjects. No other intergroup comparisons were statistically significant. These results suggest noradrenergic systems are disturbed and subresponsive to stress in melancholic/psychotic depressed patients. This does not appear related to other clinical or biochemical factors.

Differences and variability in plasma noradrenaline between depressive and anxiety disorders

Plasma noradrenaline (NA) levels were compared between two groups of patients with major depressive disorder (melancholic/psychotic and non-melancholic), patients with general anxiety disorders and healthy controls. The melancholic/psychotic depressed group had the highest plasma NA levels. This only reached statistical significance with respect to the control group. Within the depressed group, there was no association between plasma NA levels and age, weight loss, ratings of depression, anxiety or plasma cortisol levels. Variance of plasma NA was greatest in the melancholic/psychotic depressed group. A review of previous studies shows an association between raised plasma NA, depressive illness and alterations in NA variance. This association may be limited to melancholic/psychotic depressed patients. The above findings support a dysregulated noradrenergic system in depressive illness.

Psychoneuroendocrinology of schizophrenia

The study of psychoneuroendocrinology of schizophrenia has yielded an extensive but inconclusive body of data. Investigations to date have been limited by several factors, including the confounding effects of neuroleptic drugs, methodological limitations, and lack of appreciation for the heterogeneity of the illness. Previously, the focus of research has been on the measurement of anterior pituitary hormones, guided by the assumptions that these hormones are regulated by the central nervous system (CNS) to a significant degree and that the unique anatomic relationship of the pituitary gland to the hypothalamus and the CNS is potentially relevant. Patients with schizophrenia do appear to have distinct endocrinologic profiles. However, although the hormonal differences between patients with schizophrenia and the general population appear to be subtle in magnitude. Nonetheless, investigation, and the exploration of the possible effect of gonadal and posterior pituitary hormones merits particular attention.

Are blunted dexamethasone-induced growth hormone responses unique to depression?

In health, acute administration of glucocorticoids, such as dexamethasone (DEX), leads to growth hormone (GH) secretion. Depression is characterized by blunted DEX/GH responses. In order to determine the specificity of this test for depression we administered 4 mg of oral DEX, to patients with a DSM-III-R diagnosis of depression, schizophrenia, mania and alcohol dependency syndrome. Samples for GH estimation were taken at -15 min, 0 min, +60 min, +180 min, +240 min and +300 min. GH responses were attenuated to a similar degree in depression and mania. Less marked attenuation was seen in schizophrenia while those with alcohol dependency syndrome had GH responses indistinguishable from normal volunteers. Overall, we conclude that subnormal DEX/GH secretion is not specific to depression.

Growth hormone response to growth hormone releasing hormone and to clonidine stimulation in peripubertal patients with major depressive disorder

The responses of growth hormone (GH) to administration of growth hormone-releasing hormone (GHRH-1 micrograms/kg b.w.) and of clonidine (clon-2.5 micrograms/kg b.w.) and basal levels of somatomedin C (SmC) were measured in nine peripubertal patients with Major Depressive Disorder (MDD) and in 9 age- and gender-matched controls. Basal GH and SmC levels, and GH response to GHRH did not differ in patients and controls, whereas responses to clonidine were significantly higher in some and lower in other patients than in controls.

Relationship between alpha 2-adrenergic function and suicidal behavior in depressed patients

The current main neurochemical theories of the biological correlates of suicidal behavior involve serotonergic and, to a lesser extent, dopaminergic systems. Few data are available about the possible implication of the noradrenergic function. In the present study, we assessed the growth hormone response to clonidine, a selective alpha 2-adrenergic agonist, in 15 DSM-III-R major depressive inpatients with a history of suicide attempts, compared with 15 age- and gender-matched major depressive inpatients without a history of suicidal behavior. Mean (+/- SD) growth hormone peak responses to clonidine were significantly lower in the group of suicide attempters than in the control group: 2.93 +/- 3.01 ng/ml vs. 8.28 +/- 8.15 ng/ml. Therefore, these results suggest that a blunted growth hormone response to clonidine could be a biological correlate of suicidal behavior.

Growth hormone response to clonidine in neuroleptic-free patients with multidagnostically defined schizophrenia

The role of alpha 2-adrenergic receptor sensitivity in schizophrenia was examined by measuring growth hormone (GH) response after the intravenous administration of clonidine (1.3 micrograms/kg) in 26 healthy control subjects and 26 neuroleptic-free, acutely psychotic patients with at least 1 out of 11 possible diagnoses of schizophrenia derived from a multidiagnostic psychopathological assessment. GH responses were significantly (0.01) lower than control values in schizophrenias defined by E. Bleuler, M. Bleuler, Schneider, Langfeldt, Taylor and Abrams, and Cloninger, but not in DSM-III, World Health Organization, Feighner, Kraepelian, and Research Diagnostic Criteria (RDC) schizophrenias. Eight patients with RDC schizoaffective disorder also had a blunted response. However, there were no correlations with any symptom measures. There were no differences between paranoid and nonparanoid patients, although there was a significant difference between nonparanoid patients and control subjects. These findings support the presence of noradrenergic dysfunction in some patients within the schizophrenia syndrome, possibly those whose illnesses have an affective component. The study also illustrates the need for simultaneous investigation of several different sets of diagnostic criteria for schizophrenia in neurobiological research.

Growth hormone and physiological responses to clonidine in depression

Clonidine (1.3 micrograms/kg) was administered to 62 control and 55 depressed patients free of psychoactive drugs for at least 7 days and fasted overnight. Growth hormone (GH), pulse, blood pressure and sedation were measured every 15 min for 1 h before and 2 h after clonidine infusion. GH response did not differ significantly between control and depressed subjects overall or when divided by sex. The systolic hypotensive and sedative responses were blunted in depressed subjects compared with controls; these effects appeared to be secondary to residual antidepressant drugs since the differences were only significant for those depressed subjects with short drug-free intervals. No differences between depressed subjects and controls were seen in diastolic hypotensive or bradycardic responses and no differences in GH, cardiovascular or sedative responses were found between endogenous and non-endogenous depressed subjects.

The adrenergic-cholinergic imbalance hypothesis of depression: a review and a perspective

The catecholamine deficiency hypothesis of depression was essentially based on the incidental detection of iproniazide and imipramine. However, current findings favor noradrenergic overactivity, at least in the periphery. The incidental observation of acute behavioral inhibition by centrally active cholinomimetics like physostigmine suggested a cholinergic-adrenergic balance involved in the regulation of drive and mood. Indeed, cholinomimetics seem to have acute depressiogenic and antimanic properties and, conversely, anticholinergics some acute euphoriant activity. However, time course and dose-response relationships of drugs influencing mood and drive do not favor simple concepts of too much or too little activity of one or the other transmitter system. Cholinomimetics and psychostimulants show an acute mutual antagonism, the mechanism of which is obscure. In healthy volunteers clonidine and the putative antidepressant brofaromine did not influence the effects of physostigmine. Patients with mood disorders respond supersensitively to a cholinergic challenge in terms of behavior, neuroendocrine regulation and REM sleep induction. Thus, the anticholinergic properties of tricyclics might be relevant to their antidepressant activity. However, adjunctive treatment with the cholinolytic biperiden as compared to placebo did not enhance the antidepressant efficacy of mianserin or viloxazine. This is incompatible with cholinergic overactivity contributing to the depressive state. Physostigmine induces autonomous and endocrine responses reminiscent of stress reactions. Findings in healthy volunteers suggest relationships between the sensitivity to physostigmine and personality traits like irritability and emotional lability and passive stress coping strategies. Thus, the cholinergic supersensitivity in mood disorders might be related to some personality dimension like stress intolerance rather than the depressive state itself.

Guanfacine as an alpha-2-agonist inducer of growth hormone secretion--a comparison with clonidine

Doses of 0.5 mg and 1.0 mg of the alpha-2-adrenoceptor agonist guanfacine (GUA) and NaCl were administered intravenously (IV) in a randomized order to 18 healthy male subjects. GUA induced growth hormone (GH) secretion in a dose-dependent manner without affecting blood pressure or heart rate or inducing sedation. The effects of GUA 1.5 mg i.v. was compared with those of another alpha-2-adrenoceptor agonist, clonidine (CLON) 150 micrograms i.v. in six other male volunteers. Both alpha-2-agonists increased GH to similar levels. CLON reduced both systolic and diastolic blood pressure levels, whereas GUA reduced only systolic levels. Sedation was significantly more pronounced after CLON. The results suggest that the GUA/GH-test (1.5 mg GUA i.v.) may be an alternative to the CLON/GH-test in neuroendocrine assessment of alpha-2-adrenoceptor sensitivity.

Neuroendocrine response to clonidine and 8-OH-DPAT in rats following chronic administration of desipramine or sertraline

1. Rats were administered either desipramine (DMI) or sertraline daily at doses 7.5 mg kg-1 or 10 mg kg-1, i.p., respectively and the effects on the functional state of hypothalamic neuroendocrine control mechanisms assessed by measurements of plasma hormones following acute drug challenge. The effects of treatment on gross behaviour and brain adrenoceptor density were also determined. 2. Both DMI and sertraline caused significant reduction in activity measured as ambulation and rearing at 14 days of treatment. 3. All animals were chronically cannulated after 14 days of treatment and tested for neuroendocrine response to acute i.v. clonidine (50 micrograms kg-1) or 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 250 micrograms kg-1) after 21 or more days of treatment. 4. Rats treated with DMI but not sertraline showed a virtually complete suppression of the growth hormone (GH) secretion elicited by clonidine in controls, while the secretion of corticosterone was augmented. 5. Treatment with DMI but not sertraline led to a significantly greater 8-OH-DPAT-induced secretion of prolactin than in the control rats, while the plasma concentrations of corticosterone following 8-OH-DPAT were not influenced by either DMI or sertraline treatment. 6. The density (but not the affinity) of cerebral cortical binding of [3H]-dihydroalprenolol was significantly reduced by DMI treatment. 7. These results show that DMI treatment blunted the sensitivity of post-synaptic alpha 2-adrenoceptors, accompanied by complex interactions manifested as increased responsiveness of alpha 1-adrenoceptors and 5-HT1A receptors. Sertraline had no significant neurendocrine effects at a dose which significantly reduced gross activity.

Neuroendocrine evidence for decreased function of alpha 2-adrenergic receptor after electroconvulsive therapy

Growth hormone (GH) and hypotensive responses to clonidine (150 micrograms, i.v.) were investigated before and after electroconvulsive therapy (ECT) in 16 depressed patients. Because of high baseline serum GH concentrations, results from only 10 patients could be evaluated. The level of GH secretion induced by clonidine was significantly reduced after ECT, but the hypotensive responses to clonidine remained unchanged. The results indicate downward regulation of the sensitivity of alpha 2-adrenergic receptors in the hypothalamus after ECT.

Growth hormone and other hormonal responses to clonidine in melancholic and nonmelancholic depressed subjects and controls

To study putative differences in central neurotransmitter function in depressive subtypes, growth hormone, adrenocorticotropic hormone (ACTH), cortisol, and prolactin responses to the alpha 2-noradrenergic receptor agonist clonidine (1.3 micrograms/kg i.v.) were examined in 26 subjects with major depression, 13 of whom had melancholia. The responses of 10 of these endogenous/melancholic subjects were compared with those of 10 controls who were matched to the patients on age, sex, and menopausal status. In 15 of the depressed subjects, prolactin and cortisol responses to the putative serotonergic agonist fenfluramine were also examined to test for associations between these challenges. There were no significant differences in any of the responses between melancholic and nonmelancholic depressive subgroups after controlling for age and sex. With the exception of a greater reduction in ACTH in the endogenous/melancholic subjects, there were also no significant differences in hormonal responses between these patients and controls. There was, however, a significantly greater reduction in systolic blood pressure in the control subjects. There were no significant correlations between the responses to clonidine and fenfluramine. The findings suggest that clonidine at a dosage of 1.3 micrograms/kg is neither able to differentiate reliably between depressive subtypes nor to differentiate reliably between depressed and control subjects.

Blunted growth hormone and prolactin responses to L-tryptophan in depression; a state-dependent abnormality

We have investigated whether attenuated growth hormone (GH) and prolactin (PRL) responses to L-tryptophan in depression return to normal with clinical recovery. Ten patients who had received intravenous infusions of L-tryptophan (100 mg/kg) when depressed were retested at least 3 months after full recovery and cessation of treatment. In recovered depressives growth hormone responses showed considerable recovery, in all but three cases to within a few units of their healthy age- and sex-matched controls. Prolactin responses increased with clinical recovery in all six male subjects. Results in females were inconclusive because of the effect of weight loss on prolactin responses. The results suggest that GH and PRL responses to tryptophan are state-dependent abnormalities rather than indicators of predisposition to depression. This allows the possibility that impaired functioning in systems with a 5HT1A or 5HT1D receptor link may be part of the causal chain in depression.

Secretion of growth hormone elicited by intravenous desipramine in the conscious, unrestrained rat

1. Acute intravenous administration of either clonidine (Clon) (50 micrograms kg-1) or desipramine (DMI) (5 mg kg-1) elicited a pulse of growth hormone (GH) and corticosterone secretion in conscious, unrestrained rats. 2. The responses to DMI were similar to those with Clon, except that the GH pulse following DMI was delayed and was not dose-dependent. 3. The GH response to DMI was inhibited by prior administration of idazoxan (1 mg kg-1) or yohimbine (0.5 mg kg-1), but not by atropine (10 micrograms kg-1), sulpiride (5 mg kg-1) or prazosin (1 mg kg-1). 4. The corticosterone secretion following DMI was not altered by prior atropine, sulpiride or prazosin, but was augmented by idazoxan (1 mg kg-1). 5. GH secretion was not influenced by atropine, sulpiride, prazosin or idazoxan given alone. Idazoxan or yohimbine given alone elicited significant secretion of corticosterone. 6. It is concluded that i.v. DMI caused an activation through indirect mechanisms of alpha 2-adrenoceptors specifically involved in hypothalamic-pituitary regulation of GH release and also a distinct, independent and transient generalized activation of the pituitary-adrenal axis.

Hormonal responses to clonidine and urinary MHPG in delusional and nondelusional melancholic patients: a placebo-controlled study

The growth hormone (GH) and cortisol responses to intravenous clonidine (0.15 mg) treatment of 25 melancholic patients, 12 with and 13 without delusions, were studied with placebo control. The baseline concentrations of the main noradrenaline metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG) were also estimated in urine. Cortisol plasma levels decreased significantly and equally after both placebo and clonidine. Baseline cortisol levels correlated positively with urinary MHPG. Clonidine did not increase GH levels significantly over time compared with placebo. Delusional melancholic patients tended to have smaller GH responses to clonidine than nondelusionals (F = 2.18, P = 0.06). There were no differences in GH response to clonidine between high and low MHPG excretors.

Monoamines and abnormal behaviour. A multi-aminergic perspective

Classical nosology has been the cornerstone of biological psychiatric research; finding biological markers and eventually causes of disease entities has been the major goal. Another approach, designated as 'functional', is advanced here, attempting to correlate biological variables with psychological dysfunctions, the latter being considered to be the basic units of classification in psychopathology. Signs of diminished DA, 5-HT and NA metabolism, as have been found in psychiatric disorders, are not disorder-specific, but rather are related to psychopathological dimensions (hypoactivity/inertia, increased aggression/anxiety, and anhedonia) independent of the nosological framework in which these dysfunctions occur. Implications of the functional approach for psychiatry include a shift from nosological to functional application of psychotropic drugs. Functional psychopharmacology will be dysfunction-orientated and therefore geared towards utilising drug combinations. This prospect is hailed as progress, both practically and scientifically.

Hormonal responses to fenfluramine in depressive subtypes

In order to study putative differences in central neurotransmitter function in depressive subtypes, serum cortisol and prolactin responses to the putative serotonin agonist fenfluramine were examined in 30 subjects with major depression. Patients with endogenous depression (melancholia) as defined by each of ICD-9, DSM-III, RDC and Newcastle scale demonstrated a reduced prolactin response to 60 mg oral fenfluramine when compared with non-endogenous subjects. This was independent of either prolactin or cortisol baseline levels, and indicates that there are differences in brain neurotransmitter function in the endogenous and non-endogenous subtypes of depression. Basal prolactin levels were reduced in bipolar compared with unipolar subjects, and delusional compared with non-delusional patients, although there were no differences in the prolactin responses to fenfluramine between these subgroups. Basal cortisol levels and cortisol response to fenfluramine did not distinguish between any of the subtypes.

Comparison of growth hormone response after clonidine and insulin hypoglycemia in affective illness

Abnormal growth hormone (GH) responses have been observed after several neuroendocrine challenge tests. In the present study, we examined the relationship between GH response after clonidine and insulin administration within the same subject to see if consistent response patterns were evident. Though there was a significant reduction in the mean GH response after clonidine (p = 0.0002), similar differences were not observed after insulin (p = 0.10). Furthermore, there were no apparent within-subject correlations for GH response between the clonidine and insulin challenge tests. Although the present findings indicate an inherent variability in GH response patterns after different neuroendocrine challenge tests, it appears from prior studies that GH may be more consistently blunted after clonidine in depression when compared to other GH provocative tests.

Responses of growth hormone to desipramine in endogenous and non-endogenous depression

Desipramine, a monoamine reuptake inhibitor, was used to stimulate release of growth hormone (GH) in 29 DSM-III major depressives and in 10 healthy controls. Eighteen of the depressives showed a blunted response. The GH-stimulation test was unable to distinguish endogenous from non-endogenous patients. The 13 dexamethasone non-suppressors were more likely to have a blunted GH response than the 14 suppressors. The results indicate that at least a subset of non-endogenous depressives have significant neuroendocrine abnormality.

Growth hormone dysregulation in children with major depressive disorder

The growth hormone response to stimulation with oral clonidine and L-dopa was measured in 14 boys with major depressive disorder (MDD) and 15 normal boys. The six MDD boys who were prepubertal or in early puberty were significantly lower than the 10 normal subjects of this age in peak growth hormone response following clonidine administration (p = 0.029) and area under the curve for clonidine (p = 0.030) and L-dopa (p = 0.028). The eight later puberty MDD boys did not differ from the five later puberty normal boys on any measures.

[3H]yohimbine binding to platelet alpha 2-adrenoceptors in depression

[3H]Yohimbine binding to platelet alpha 2-adrenoceptors was studied in depressed patients and healthy volunteers. Where possible platelet binding measurement was repeated in depressed patients following treatment. Bmax of [3H]yohimbine binding did not differ significantly between depressed patients and control subjects and did not change with treatment in depressed patients. KD was significantly lower in female depressed patients, particularly in those who were post-menopausal. Multivariate analysis showed significant effects on KD of depression, season of testing and assay protein concentration.

Growth hormone response to clonidine in untreated depressed patients

Growth hormone (GH) responses to i.v. clonidine administration (150 micrograms) were compared in untreated depressed patients and controls. There were 8 controls (6 males, 2 females), 16 patients with a major depressive episode (8 males, 8 females), and 16 matched patients with a minor depressive episode according to Research Diagnostic Criteria. Differences in the GH response to clonidine only occurred between male patients and controls. These results suggest that endocrinological variables are important in the interpretation of this neuroendocrine test. Findings in the subgroup of unmedicated male patients with a nonendogenous major depressive episode support the hypothesis of decreased noradrenergic receptor sensitivity.

Multiple hormone responses to clonidine administration in depressed patients and healthy volunteers

Abnormalities in several hypothalamic-pituitary-target organ axes in depression may reflect alterations in central neurotransmitter receptor function. As the alpha 2-adrenergic receptor has been implicated in a variety of neuroendocrine abnormalities in depression, we assessed the role of alpha 2-adrenoceptor dysfunction in mediating response abnormalities of growth hormone, cortisol, and prolactin after intravenous clonidine administration (an alpha 2-adrenergic receptor agonist) in 18 patients with major depression (12 with melancholic features, 6 without melancholic symptoms) and 9 healthy volunteers. In particular, we examined the hypothesis that these abnormalities might be more evident in patients with DSM-III melancholic depression. After clonidine, the mean growth hormone response was significantly lower in melancholic depressives compared to controls (p = 0.02), and the shape of the growth hormone response profile was also significantly different in melancholic patients (p = 0.04). There was an overall decrease in the mean cortisol concentration after clonidine in melancholic patients and control subjects (p = 0.02), as well as a larger cumulative prolactin response in melancholic patients compared to those without melancholic features (p = 0.02). The present results confirm prior observations of a blunted growth hormone response after clonidine and suggest that alterations in alpha 2-adrenergic receptor activity might also contribute to several neuroendocrine abnormalities in patients with melancholic depression.

Tricyclic wash-out and growth hormone response to clonidine

We have observed a significantly higher growth hormone (GH) response to clonidine administration (150 micrograms i.v.) in 14 patients with a major depressive disorder who had never received antidepressant therapy than in 14 matched depressive patients who had not received tricyclic drugs for at least 15 days. Compared with a control group of eight subjects, untreated depressed patients, as a group, had a normal response, while matched patients had markedly blunted response. Results for the group of untreated depressed patients showed that some patients had a blunted response while others had a response in the normal range. The results suggest that studies on the GH response to clonidine in psychiatric patients need to take into account the confounding and long-lasting effects of tricyclics.

Morning and evening adrenocortical responses to ACTH stimulation in endogenously depressed patients: a preliminary report

Adrenocortical stimulation with ACTH both in the morning (M-test) and in the evening (E-test) and the dexamethasone suppression test were carried out in patients suffering from endogenous depression (DEP) and normal controls (NOR). A greater cortisol release in DEP was recognized than in NOR in the M-test, an earlier peak response of DEP was shown in the M-test than in the E-test, and a lack of association between hypersecretion of cortisol during depression and cortisol output after ACTH administration was noted. These findings, together with the results of DST, suggest that excessive activity of the hypothalamic-pituitary-adrenal (HPA) axis in depression may result, partly, from adrenocortical hyperresponsiveness.

Alpha 2-adrenergic receptor sensitivity in depressed patients: relation between 3H-yohimbine binding to platelet membranes and clonidine-induced hypotension

Alpha 2-adrenergic receptor changes during antidepressant treatment were studied using 3H-yohimbine binding to human platelet membranes and clonidine-induced hypotension. Twenty-six patients with major depressive disorder (MDD) participated for 4-6 weeks in a trial of imipramine (2.5 mg/kg/day), tyrosine (100 mg/kg/day), or placebo. Alpha 2-adrenergic receptors measured by 3H-yohimbine binding were not significantly changed following antidepressant treatment. Similarly, clonidine-induced hypotension did not differ significantly following treatment. No measure of alpha 2-adrenergic receptor sensitivity was significantly correlated with clinical improvement. The correlation between platelet receptor binding and clonidine-induced hypotension was not statistically significant, even though both tests are considered to be measures of alpha 2-adrenoceptor sensitivity.

Blunted response of growth hormone to clonidine and apomorphine in endogenous depression

We measured the growth hormone (GH) response to clonidine (an alpha-2-adrenergic agonist) and to apomorphine (a dopaminergic agonist) in 15 major endogenous and 15 minor depressive in-patients matched for gender and age. Results showed a significantly smaller GH response in the major depressives to both clonidine (P less than 0.01) and apomorphine (P less than 0.001). No significant difference existed between the two groups with regard to changes in blood pressure and pulse rate during either test. While major depressives showed a trend toward smaller sedative side-effects than minor depressives after clonidine, they showed significantly smaller sedative and gastro-intestinal side-effects after apomorphine. No significant correlation was present either in the major depressive or in the minor depressive group between the GH responses following clonidine and apomorphine challenges. These results support the hypothesis of both noradrenergic and dopaminergic neurotransmitter disturbances in major depression, with individual variability with regard to those biochemical anomalies.

Clonidine challenge testing of alpha-2-adrenoceptor function in man: the effects of mental illness and psychotropic medication

The clonidine challenge test is a means of assessing alpha-2-adrenoceptor sen sitivity in man. We review studies which have used this test to investigate central alpha-2- adrenoceptor changes in psychiatric illness, and to determine receptor changes after adminis tration and withdrawal of psychotropic treatments. Patients with severe depression show evidence of reduced alpha-2-adrenoceptor sensitivity, especially a reduced growth hormone response to clonidine. This may delineate a subgroup of patients with severe depressive illness from those with milder depression, and may even provide a trait marker for some depressed patients. Patients with panic disorder show evidence of subsensitivity to some and supersensitivity to other clonidine-induced responses. Other disorders, although less well investigated, may have abnormal test responses which may provide additional information about their cause and treatment. Changes in response after drug treatment have provided important information on the mode of action of antidepressants, and have suggested that noradrenergic function is altered by a variety of different antidepressants.

Growth hormone response to clonidine after recovery in patients with endogenous depression

The growth hormone response to clonidine was measured in ten drug-free recovered patients, seven of whom had previously been tested when endogenously depressed, and compared with the response in ten individually matched controls. In eight of the patients there was an impairment of the growth hormone response, despite clinical recovery, although the hypotensive effect of clonidine in these patients was normal. This is suggestive of a persisting abnormal alpha2-adrenoceptor function in forebrain regions after recovery from an episode of endogenous depression, and may represent a trait marker for this condition.

Neuroendocrine evaluation of catecholaminergic neurotransmission in mania

Several lines of evidence suggest catecholamine overactivity (noradrenergic and/or dopaminergic) in mania. We studied the growth hormone (GH) response to clonidine (an alpha-adrenergic agonist) and apomorphine (a dopaminergic agonist) in seven inpatients meeting Research Diagnostic Criteria for mania. They had been completely drug free for at least 3 months before the neuroendocrine procedures and were age- and sex-matched to seven major depressive and seven minor depressive inpatients, drug free for at least 2 weeks. GH was assayed every 20 min for 40 min before and 120 min after either clonidine (0.15 mg i.v.) or apomorphine (0.5 mg s.c.), with an interval of at least 2 days between the tests. The three groups differed significantly in the GH peak response: after clonidine (mean +/- SD), 3.2 +/- 2.4 ng/ml in manics, 3.2 +/- 2.4 ng/ml in major depressives, and 13.2 +/- 8.7 ng/ml in minor depressives; after apomorphine, 10.5 +/- 7.4, 3.2 +/- 1.9, and 26.9 +/- 15.8, respectively. While there were significant differences between manics and minor depressives and between major and minor depressives after both clonidine and apomorphine, manics did not significantly differ from major depressives on either test. These results do not provide neuroendocrine support to the catecholaminergic hypothesis of manic disorders.

Effects of desipramine treatment upon central adrenoceptor function in normal subjects

Six normal subjects were given clonidine infusions after 0, 1 and 3 weeks of treatment with desipramine (2 mg/kgm) and at 1 and 3 weeks after withdrawal from desipramine. The sedative and hypotensive effects of clonidine were inhibited after one and three weeks of desipramine treatment, and returned to normal after stopping treatment without any rebound increase. Such a time-course can be explained in terms of the acute effects of the drug, no adaptive changes at receptors need be invoked. By contrast, the growth hormone response to clonidine tended to be increased after one week of desipramine, reduced after three weeks of treatment, and further reduced after discontinuation. Such a time-course is consistent with an adaptive down regulation at alpha 2 adrenoceptors in response to their acute stimulation, due to noradrenaline re-uptake blockade.

A comparison of the growth hormone responses to clonidine and apomorphine in the same patients with endogenous depression

The growth hormone responses to clonidine (1.3 micrograms/kgm) and apomorphine (0.005 mg/kgm) have been measured in 8 drug free patients with endogenous depression. In these patients the growth hormone responses to clonidine were significantly smaller than to apomorphine. As these doses of clonidine and apomorphine have previously been reported to cause similar growth hormone responses in normal subjects, these findings support the hypothesis of a defect in the adrenergic but not the dopaminergic regulation of growth hormone in patients with endogenous depression.