Elucidation of biochemical basis of the antidepressant action of electroconvulsive therapy by human studies

A variety of direct and indirect human studies indicate that electroconvulsive therapy (ECT) enhances transmission in a number of key transmitter systems in the brain. These include the noradrenergic system, the serotonergic system, and the GABAergic and dopaminergic systems. On the other hand, ECT probably reduces cholinergic transmission. The enhanced transmission effects have been related to the antidepressant effect of ECT, whereas the cholinergic effect has been attributed to its effects on memory and cognition as well as depression. This paper will briefly review the research methodologies and results from clinical studies of neurotransmitter effects of ECT. Promising future directions of research will be indicated.

Neuroendocrine responses to fenfluramine challenge are influenced by exposure to chronic social stress in adult male cynomolgus macaques

This study was designed to investigate the effect of chronic social stress on central serotonergic responsivity in adult male cynomolgus monkeys (Macaca fascicularis). The influences of social stress and dominance status (social rank) on adrenocorticotropin hormone (ACTH) and cortisol responses to acute administration of an indirect serotonergic agonist (fenfluramine) were evaluated in 75 cynomolgus macaques that were housed in five-member social groups for 28 mo. These groups either remained stable in composition (No-Stress) or had their composition periodically reorganized in the first (Early-Stress) or second (Late-Stress) halves of the study. At the end of the 23rd month, a fenfluramine challenge was done. Animals in the Late-Stress condition had significantly higher ACTH responses compared to those in the No-Stress condition (p < .05) and significantly higher cortisol responses compared to those in the Early-Stress condition (p < .05). No differences between dominant and subordinate animals in ACTH or cortisol responses to challenge were identified. These data suggest that social stress produces a "state"-related augmentation of hypothalamic-pituitary-adrenal responsivity to fenfluramine (serotonergic) challenge in cynomolgus macaques.

Quantitative autoradiography of alpha 1- and alpha 2-adrenergic receptors in the cerebral cortex of controls and suicide victims

Alterations in both serotonergic and noradrenergic indices have been found in the brain of suicide victims. In order to better understand the role of the noradrenergic system in suicide, we carried out quantitative autoradiography of alpha 1- and alpha 2-adrenergic receptors using [3H]prazosin and [3H]-p-aminoclonidine respectively. We compared the distribution and relative density of these receptors in the prefrontal (PFC) and alpha 1-adrenergic receptors in the temporal cortex (TC) of suicide victims and controls matched for postmortem delay, age, side of brain and sex. We found that: (1) the laminar patterns of alpha 1-adrenergic receptors in the PFC (n = 20) and the TC (n = 16) were different (P = 0.022); (2) there was a 37% increase in alpha 1-adrenergic binding corresponding to layers IV-V of PFC of suicide victims compared to controls (P = 0.029); (3) the TC had a greater density of alpha 1-adrenergic binding sites than the PFC across all cortical layers (P = 0.006); (4) alpha 2-adrenergic binding sites had a specific laminar distribution in the PFC (n = 24) which did not differ in controls and suicide victims; (5) binding to alpha 2-adrenergic sites in the PFC of suicide victims did not differ from controls; and (6) norepinephrine concentrations in the same brain areas were elevated in the suicide group compared to controls, but did not correlate with binding to alpha 1- or alpha 2-adrenergic sites. The increase in [3H]prazosin (to alpha 1-adrenergic receptors) but not in [3H]-p-aminoclonidine (to alpha 2-adrenergic receptors), and in norepinephrine concentrations in the brain of suicide victims provides further evidence for an association between suicide and altered brain noradrenergic function. Future studies must determine whether these changes in brain noradrenergic function indicate increased or decreased transmission.

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

The effects of fenfluramine, an indirect serotonergic agonist, on electroencephalographic sleep and prolactin secretion were assessed in 12 unmedicated inpatients with a primary diagnosis of major depressive episode. Compared to prefenfluramine profiles, sleep studies performed following fenfluramine administration showed a statistically significant reduction of slow-wave sleep (SWS) (p < 0.001) and a corresponding increase in percentage of stage-2 sleep (p < 0.007). Automated delta wave counts per min decreased significantly during the first nonrapid eye movement (NREM) period (p = 0.04), and automated rapid-eye movement (REM) counts were also decreased in the second REM period (p = 0.02). These effects on sleep electroencephalogram (EEG) did not correlate significantly with another measure of serotonergic responsivity, namely peak prolactin level following fenfluramine, nor with the severity of depression. The reductions in SWS and REM counts are proposed to be the result of time-dependent changes in serotonergic neurotransmission following the administration of fenfluramine. These findings are consistent with earlier work suggesting a role for serotonin in initiation and regulation of SWS and REM sleep.

Computerized three-dimensional reconstruction reveals cerebrovascular regulatory subregions in rat brain stem

Three-dimensional wireframe reconstructions were used to examine the relationship between the anatomical localization of electrode sites and the cerebrovascular response which was elicited by electrical stimulation of the dorsal raphe nucleus (DRN). Reconstructions of the rat brain and DRN were done from atlas plates and from Nissl-stained coronal sections (100-micron increments). Data points were entered and three-dimensional reconstructions were performed using commercially available software and a personal computer. Display of the entire brain yielded views which obscured visualization of the DRN. The data file was edited to reduce the number of contours without affecting the display resolution of the DRN. Selective display of the DRN and electronic rotation from the coronal to a sagittal view revealed a functional organization of the cerebral blood flow responses which was not apparent in two-dimensional coronal sections.

Low versus high prolactin responders to fenfluramine challenge: marker of behavioral differences in adult male cynomolgus macaques

Prolactin response to acute administration of fenfluramine hydrochloride is considered an indirect assessment of "net" central serotonergic activity. This study compared behavioral characteristics of adult, male cynomolgus macaques (Macaca fascicularis) having "low" or "high" prolactin responses to fenfluramine challenge. The subjects were 75 animals housed in five-member social groups for 28 months. In month 23, prolactin responses to fenfluramine challenge were evaluated. Observations of specific behaviors (aggressive, submissive, affiliative, and nonsocial) were made three times per week on animals in each social group. The dominance status of each animal within a social group was assessed at weekly intervals. Low prolactin responders had a significantly higher index of "overt" aggression (ratio of fights involving physical contact and chasing or lunging/all forms of aggressive behavior) compared to high prolactin responders (p < .03). There were no differences in the dominance status of low and high responders (p = .34). Furthermore, low responders were more socially withdrawn than high responders, as they spent significantly more time alone (passive or neutral state; p < .03) and less time in passive body contact with other animals than high responders (p < .05). These data support the hypothesis that reduced central serotonergic activity in nonhuman primates is associated with a high level of overt aggression and a low level of positive social interaction.

Electroconvulsive shock increases tyrosine hydroxylase and neuropeptide Y gene expression in the locus coeruleus

Electroconvulsive seizures (ECS) increase tyrosine hydroxylase (TH) activity in the locus coeruleus (LC) but not in the substantia nigra (SN). To determine whether new enzyme synthesis contributes to the increase in TH activity, we carried out in situ hybridization histochemistry to determine the effect of ECS on TH mRNA levels in the LC and SN. The effect of ECS on neuropeptide Y (NPY) mRNA levels in the LC was also studied because NPY coexists with norepinephrine in the LC neurons and has been implicated in depressive disorders. A significant increase was observed in TH mRNA and NPY mRNA levels in LC neurons in the ECS group. There was no difference between TH or NPY mRNA levels in the left and right LC. No change was observed in TH mRNA expression in the SN compacta or SN reticulata. We conclude that the regionally selective increase in TH activity after ECS is at least partly due to increased gene expression and that NPY gene expression is regulated in a similar fashion following ECS.

Factor composition of the Suicide Intent Scale

An exploratory analysis of the Suicide Intent Scale was performed on a sample of 98 psychiatric inpatients who had made suicide attempts. The factor analysis was performed using a method for polychotomous data, and resulted in a two-factor solution. The Lethal Intent factor contained items pertaining to the subjective level of lethal intent, while the Planning factor contained items largely related to objective planning for the attempt. Preliminary analysis of these factors suggest that the Suicide Intent Scale can be used to evaluate two separate aspects of suicidal behavior.

Antidepressant medications and the relative risk of suicide attempt and suicide

OBJECTIVE

Suicide by drug overdose is a major public health problem, and antidepressant medications are the most common agent involved. European studies suggest differences in the rates of suicide by overdose among antidepressants, but no reports have been published for the United States. We estimated the comparative risks of suicide attempts and suicides, and the relative risk of fatality in the event of an overdose for the major antidepressants currently marketed in the United States.

DATA SOURCES

Information regarding suicide attempts and suicides by antidepressant overdose was obtained from the published reports of the Drug Abuse and Warning Network and the annual report of the American Association of Poison Control Centers, and corrected for differences in total annual prescriptions using data from the National Prescription Audit.

RESULTS

The risk of a suicide attempt did not appear to differ among antidepressants. The tricyclic antidepressants were associated with a higher rate of death in the event of an overdose than the newer nontricyclic antidepressants in both the annual report of the American Association of Poison Control Centers and the Drug Abuse and Warning Network data. The chance of death after an overdose was greater for desipramine hydrochloride than for other tricyclics.

CONCLUSION

The higher risk of suicide with tricyclics vs nontricyclics may be explained by a higher rate of death from overdose rather than more suicide attempts. Tricyclics carry the risk of greater cardiotoxicity. The basis for the even higher rate of death/overdose of desipramine is not known and requires further research. If these findings are replicated in a case-control study design, they have important implications for the choice of an antidepressant for the depressed patient at risk for suicidal behavior.

Platelet and whole blood serotonin content in depressed inpatients: correlations with acute and life-time psychopathology

Platelet or whole blood serotonin content did not differ significantly in patients with major depression compared to healthy controls, but within the patient group, platelet serotonin levels correlated negatively with severity of depression (r = -0.49, p = 0.007). Levels were 39% lower in patients who had made a suicide attempt compared to nonattempter patients (47.2 +/- 27.3 versus 77.6 +/- 41.7 ng/10(8) platelets, p = 0.04). Conversely, comorbid borderline personality disorder (85.3 +/- 41.5 ng/10(8) platelets) was associated with 31% greater platelet serotonin content than nonborderline patients (58.9 +/- 31.1 ng/10(8) platelets) and 27% greater than healthy controls (62.4 +/- 19.8 ng/10(8) platelets). A pronounced seasonal variation in whole blood and platelet serotonin content was found in both patients and controls, largely due to lower levels in summer. Excluding cases tested in the summer abolished the statistically significant differences in patients with and without comorbid borderline personality disorder (BPD). Nevertheless, BPD attempters had lower serotonin levels than BPD nonattempters but higher serotonin levels than non-BPD attempters. Current hostility and a life-time history of aggression were positively correlated with platelet serotonin content (r = 0.44, p = 0.04 and r = 0.41, p = 0.06). This study provides evidence for an association between lower platelet serotonin content and depression and suicidal behavior, and association of higher platelet serotonin content and comorbid borderline personality disorder and behavior traits such as aggressivity.

Role of the dopaminergic system in depression

A hypothesis implicating dopamine in depression was proposed over 15 years ago (Randrup et al 1975). The identification of multiple new subtypes of dopamine receptors and evolving views regarding the function of the dopamine systems in the brain require a reexamination of this hypothesis. Results from studies in depression, Parkinson's disease, and animal models of depression suggest a deficiency of dopamine in depression. Dopamine precursors, dopamine agonists, and dopamine reuptake inhibitors show therapeutic efficacy in depression. Electroconvulsive therapy (ECT) and standard pharmacological antidepressants enhance dopamine function. Studies using receptor-specific drugs in clinical trials and neuroimaging studies are needed to further clarify the role of dopamine in depression.

Regulation of cortical blood flow by the dorsal raphe nucleus: topographic organization of cerebrovascular regulatory regions

We examined in rat: (1) the time-course and magnitude of change in cortical blood flow (CoBF) following electrical stimulation of the dorsal raphe nucleus (DRN) and (2) whether DRN lesions affect resting CoBF or the cerebrovascular response to CO2. Animals were anesthetized (chloralose), paralyzed, and artificially ventilated. The effect of stimulus frequency (1-200 Hz) and intensity (10-100 microA) on arterial pressure, heart rate, and CoBF was examined; lesions were made electrolytically. CoBF was measured using a laser-Doppler flowmeter with the probe placed extradurally over the parietal sensorimotor cortex. The DRN was computer reconstructed in three dimensions from Nissl stained coronal sections for localization of electrode placements. Brief stimuli (8 s; n = 6) elicited frequency and intensity-dependent increases in arterial pressure, heart rate, and CoBF. Sustained intermittent trains of stimuli of rostral DRN (200 Hz; 1 s on/1 s off; 70 microA) elicited a decrease (85 +/- 12% of baseline; n = 9) in CoBF (p less than 0.05) while stimulation in caudal DRN resulted in increased CBF (126 +/- 13% of baseline; n = 9). Phenylephrine infusion (0.1-1 microgram; i.v.; n = 8) increased arterial pressure and CoBF less than that elicited by brief DRN stimulation (p less than 0.05). DRN lesions did not affect resting CoBF (140 +/- 25 perfusion units (PU) before; 127 +/- 16 PU after DRN lesion; p greater than 0.05, n = 5) or mean arterial pressure (127 +/- 13 before; 120 +/- 11 after); nor did it affect the cerebrovascular response to change in arterial PCO2. Sustained intermittent stimulation of the DRN can evoke either increases or decreases in CoBF depending on the anatomical sublocalization. The DRN does not tonically maintain resting CoBF, nor participate in the cerebrovascular response to change in PCO2.

Relationship between central and peripheral serotonin indexes in depressed and suicidal psychiatric inpatients

Serious suicidal behavior, affective disorders, and a variety of other psychopathologic behaviors and syndromes have been found to correlate with measures of the serotonin system. Clinical studies have employed a range of serotonin indexes, including the cerebrospinal fluid level of 5-hydroxyindoleacetic acid, the prolactin response to serotonin agonists, such as fenfluramine hydrochloride, and platelet serotonin-related proteins or serotonin content. Many of these indexes are correlated with suicidal behavior, but the interrelationship of these biologic measures has been uncertain. We studied the relationship of a series of serotonin indexes in patients in whom these measures were correlated with suicidal behavior. A positive correlation was found between cerebrospinal fluid 5-hydroxyindoleacetic acid and the maximal prolactin response to fenfluramine but not with platelet serotonin2 receptor indexes. The fenfluramine-stimulated maximal prolactin response correlated with platelet serotonin2 receptor number, particularly in older patients. We conclude that cerebrospinal fluid 5-hydroxyindoleacetic acid measurements cannot be replaced but can be complemented by less invasive procedures, such as a fenfluramine challenge test or platelet serotonin2 measures, in the study of the relationship of the serotonin system to psychiatric disorders.

The effect of access to lethal methods of injury on suicide rates

The relationship between the availability of lethal methods of injury and suicide rates is an important, but unresolved question. We investigated this relationship by prospectively classifying lethal methods according to their accessibility in the five counties of New York City. These counties have both similarities and differences in the proportion of their populations with access to specific lethal means. We then compared the age- and gender-adjusted method-specific suicide rates of these counties. There were marked differences in overall crude suicide rates among the five counties. The counties had similar suicide rates involving methods that were equally accessible to all persons in each county (eg, hanging, laceration, suffocation, and burns) as well as methods that were accessible to a smaller, but similar proportion of the population in each county (eg, firearms and drowning in waterways). Virtually all of the differences in overall suicide risk among counties were explained by differences in rates involving methods that were differentially available in the counties, principally fall from height, overdose of prescription medications, and carbon monoxide poisoning. We conclude that differences in suicide rates between communities are, in large part, due to differences in accessibility to lethal methods of injury. Therefore, systematic studies should evaluate the effect of reducing accessibility to specific lethal means on suicide rates.

Integration of neurobiology and psychopathology in a unified model of suicidal behavior

Suicidal behavior is the result of a combination of factors that span the domains of psychopathology, genetics, early life experience, family interactions, social stress, physical illness, and neurobiology. To develop predictive and explanatory models of suicidal behavior it is necessary to consider all of these domains. A stress-diathesis model is proposed that classifies risk factors for suicidal behavior into those that are trait-dependent and those that are state-dependent. The timing of suicidal behavior is determined by state-dependent factors. The relationship of psychopathologic factors such as severity of depression or anxiety to suicide will be discussed. Biologic changes that correlate with suicide may be either state- or trait-dependent. Particular emphasis will be given to changes in the serotonin system and how these may represent a constitutional risk factor as opposed to a state-dependent risk factor for suicidal behavior.

Alterations in monoamine receptors in the brain of suicide victims

Suicide has been linked to alterations in the serotonergic and noradrenergic systems. Using in vitro quantitative receptor autoradiography, we compared the binding of 125I-lysergic acid diethylamide (5-hydroxytryptamine-2 sites) and 125I-pindolol (beta-adrenergic sites) with slide-mounted sections from the prefrontal and the temporal cortex of a group of suicide victims, matched to control specimens on postmortem interval, age, sex, and race. A specific laminar distribution of 5-hydroxytryptamine-2 binding was found in both groups, with layers III and IV having the highest level of binding, but beta-adrenergic binding did not differ across cortical layers. Binding to both 125I-lysergic acid diethylamide and 125I-pindolol was increased in the prefrontal cortex of the suicide victims, whereas only beta-adrenergic binding was increased in the temporal cortex of the suicide group.

Prevalence of cocaine use among residents of New York City who committed suicide during a one-year period

OBJECTIVE

In the mid-1980s the form of cocaine called "crack" became widely available in New York City. The authors sought to determine the prevalence of cocaine metabolites detected at autopsy in persons who committed suicide in New York City during this period.

METHOD

Individual reviews of the autopsy and toxicological records of all persons under the age of 61 who had committed suicide in the city during a 1-year period were conducted to determine demographic characteristics, suicide methods, and cocaine and alcohol use at the time of death.

RESULTS

In one of every five cases studied, the person who committed suicide had used cocaine within days of his or her death. The prevalence of cocaine use among young Hispanic males who committed suicide was 45%. Persons who were young, black, or Hispanic and who had used alcohol immediately before the fatal injury were most likely to have been recent cocaine users. After controlling for demographic variables and ethanol use, the investigators found that individuals who committed suicide with firearms were twice as likely to have used cocaine as those who used other methods.

CONCLUSIONS

In contrast to the results of regional and household surveys during this period, which suggested that the current prevalence of cocaine use in New York City was 3%-5%, these results suggest a high prevalence of cocaine use in the days immediately preceding death by young persons who commit suicide. Additional studies are needed to determine how cocaine may act as a risk factor for suicide.

Self-mutilation in personality disorders: psychological and biological correlates

OBJECTIVE

The goal of this study was to determine whether self-mutilators with personality disorders differ from nonmutilators with personality disorders in impulsivity, aggression, and other psychopathology and whether serotonergic dysfunction contributes to self-mutilation.

METHOD

Twenty-six self-mutilators with personality disorders were matched to 26 control subjects with personality disorders for gender, age, education, axis I diagnosis of affective disorder, and axis II diagnosis of personality disorder. Numerous indexes of psychopathology as well as CSF 5-hydroxyindoleacetic acid (5-HIAA) levels and platelet imipramine binding sites (Bmax) and affinity (Kd) were determined.

RESULTS

Self-mutilators had significantly more severe character pathology, had greater lifetime aggression, and were more antisocial than the control subjects. The self-mutilators scored higher on the Hamilton Rating Scale for Depression but not on the Beck Depression Inventory or the Beck Hopelessness Scale. The two groups did not differ on the Buss-Durkee Hostility and Guilt Inventory or on the Sensation Seeking Scale. The degree of self-mutilation was significantly correlated with impulsivity, chronic anger, and somatic anxiety. Both self-mutilation and impulsivity showed significant negative correlations with Bmax, although the two groups did not differ in CSF 5-HIAA levels or in platelet imipramine binding.

CONCLUSIONS

The results demonstrate the contribution of severe character pathology, aggression, impulsivity, anxiety, and anger to self-mutilation and provide preliminary support for the hypothesis of underlying serotonergic dysfunction facilitating self-mutilation.

Simultaneous effects of the platelet 5-HT2 and alpha 2-adrenergic receptor populations on phosphoinositide hydrolysis

The interaction of multiple receptor populations on a common second messenger system is a critical aspect of cell function and may be involved in pathology. We studied the interactions of the 5-HT2, alpha 2-adrenergic and prostaglandin (PGI2) receptors on phosphoinositide (PI) turnover in human platelets. Serotonin and epinephrine (EPI) stimulated PI hydrolysis in a dose-dependent manner. The PI turnover response to serotonin was mediated by the 5-HT2 receptor. The PI response to EPI was mediated by alpha 2-adrenergic receptors. An additive PI turnover response was generated by the combination of 5-HT and EPI. The sum of the maximal responses to 5-HT (72.5 +/- 4.9%) and EPI (56.0 +/- 4.2%) approximated the maximal response (129.3 +/- 9.5) to the combination. Prostacyclin (PGI2) at 1 microgram/mL reduced PI turnover by 21.8 +/- 1.1%. The PI response to 5-HT and EPI was not significantly altered once the reduction in the baseline PI turnover by PGI2 is taken into account. Similarly, PGI2 did not reduce PI hydrolysis stimulated by a combination of 5-HT (0.2 mM) and EPI (0.1 mM) once the decrease in baseline was taken into account (p greater than 0.20). The summation of serotonin stimulation of PI turnover by a combination of both epinephrine and serotonin was blocked by either yohimbine or ketanserin. These studies indicate: (1) the pool of phospholipases appears to exceed the maximal capacity of the individual alpha 2-adrenergic and 5-HT2 receptor populations to activate this second messenger system. (2) inhibition of serotonin or epinephrine-stimulated PI turnover by prostacyclin is due to a lowering of basal PI turnover. Future studies should examine other cell systems to assess the generalizability of these findings regarding the differences in effects on a second messenger system when activated by one receptor population as opposed to two different receptor types.

Biology of elderly suicide

Most studies of suicide in younger patients have demonstrated significant alterations in the serotonin system. Although a high percentage of completed suicides occur in late-life, to date very few studies of the biology of suicide have focused on this age group. This chapter describes age-related changes in the central nervous system pertinent to the biology of suicide, then reviews post-mortem biological studies of the brains of suicides and suicide attempters. As suicide attempts in the elderly are characterized by the use of violent means, biologic studies of impulsive violence are discussed. Finally we describe data on the effect of degenerative diseases on the serotonin system and the possible link to increased suicidal behavior in affected patients. This review underscores the need for further study of the biology of suicide in the geriatric age group.

Neuroendocrine and behavioral responses to challenge with the indirect serotonin agonist dl-fenfluramine in adults with obsessive-compulsive disorder

Neuroendocrine and behavioral responses to a single 60-mg oral dose of the indirect serotonin agonist dl-fenfluramine were assessed in unmedicated adults with obsessive-compulsive disorder (OCD) and neuroendocrine results contrasted with those in normal control subjects. Net fenfluramine-induced prolactin release did not differ significantly between OCD patients and normal controls. Prolactin responses in the OCD group were not significantly correlated with baseline Yale-Brown Obsessive Compulsive Scale scores for either obsessions or compulsions, but were positively correlated with the baseline Hamilton Depression Scale score and Hamilton Anxiety Scale score. No clear difference in the severity of patients' obsessions or compulsions was found following challenge with fenfluramine versus placebo. Although the present study does not demonstrate a serotonergic abnormality in OCD, this may be more a reflection of limitations of the test procedures than evidence that central nervous system (CNS) serotonergic function is normal in the disorder.