Antidepressant withdrawal-induced activation (hypomania and mania): mechanism and theoretical significance

Acute and Persistent Withdrawal Syndromes Following Discontinuation of Psychotropic Medications

Studies on psychotropic medications decrease, discontinuation, or switch have uncovered withdrawal syndromes. The present overview aimed at analyzing the literature to illustrate withdrawal after decrease, discontinuation, or switch of psychotropic medications based on the drug class (i.e., benzodiazepines, nonbenzodiazepine benzodiazepine receptor agonists, antidepressants, ketamine, antipsychotics, lithium, mood stabilizers) according to the diagnostic criteria of Chouinard and Chouinard [Psychother Psychosom. 2015;84(2):63-71], which encompass new withdrawal symptoms, rebound symptoms, and persistent post-withdrawal disorders. All these drugs may induce withdrawal syndromes and rebound upon discontinuation, even with slow tapering. However, only selective serotonin reuptake inhibitors, serotonin noradrenaline reuptake inhibitors, and antipsychotics were consistently also associated with persistent post-withdrawal disorders and potential high severity of symptoms, including alterations of clinical course, whereas the distress associated with benzodiazepines discontinuation appears to be short-lived. As a result, the common belief that benzodiazepines should be substituted by medications that cause less dependence such as antidepressants and antipsychotics runs counter the available literature. Ketamine, and probably its derivatives, may be classified as at high risk for dependence and addiction. Because of the lag phase that has taken place between the introduction of a drug into the market and the description of withdrawal symptoms, caution is needed with the use of newer antidepressants and antipsychotics. Within medication classes, alprazolam, lorazepam, triazolam, paroxetine, venlafaxine, fluphenazine, perphenazine, clozapine, and quetiapine are more likely to induce withdrawal. The likelihood of withdrawal manifestations that may be severe and persistent should thus be taken into account in clinical practice and also in children and adolescents.

What I have learnt from helping thousands of people taper off antidepressants and other psychotropic medications

Although psychiatric drug withdrawal syndromes have been recognized since the 1950s - recent studies confirm antidepressant withdrawal syndrome incidence upwards of 40% - medical information about how to safely go off the drugs has been lacking. To fill this gap, over the last 25 years, patients have developed a robust Internet-based subculture of peer support for tapering off psychiatric drugs and recovering from withdrawal syndrome. This account from the founder of such an online community covers lessons learned from thousands of patients regarding common experiences with medical providers, identification of adverse drug reactions, risk factors for withdrawal, tapering techniques, withdrawal symptoms, protracted withdrawal syndrome, and strategies to cope with symptoms, in the context of the existing scientific literature.

Behavioral effects of Bj-PRO-7a, a proline-rich oligopeptide from Bothrops jararaca venom

The heptapeptide Bj-PRO-7a, isolated and identified from Bothrops jararaca (Bj) venom, produces antihypertensive and other cardiovascular effects that are independent on angiotensin converting enzyme inhibition, possibly relying on cholinergic muscarinic receptors subtype 1 (M1R). However, whether Bj-PRO-7a acts upon the central nervous system and modifies behavior is yet to be determined. Therefore, the aims of this study were: i) to assess the effects of acute administration of Bj-PRO-7a upon behavior; ii) to reveal mechanisms involved in the effects of Bj-PRO-7a upon locomotion/exploration, anxiety, and depression-like behaviors. For this purpose, adult male Wistar (WT, wild type) and spontaneous hypertensive rats (SHR) received intraperitoneal injections of vehicle (0.9% NaCl), diazepam (2 mg/kg), imipramine (15 mg/kg), Bj-PRO-7a (71, 213 or 426 nmol/kg), pirenzepine (852 nmol/kg), α-methyl-DL-tyrosine (200 mg/kg), or chlorpromazine (2 mg/kg), and underwent elevated plus maze, open field, and forced swimming tests. The heptapeptide promoted anxiolytic and antidepressant-like effects and increased locomotion/exploration. These effects of Bj-PRO-7a seem to be dependent on M1R activation and dopaminergic receptors and rely on catecholaminergic pathways.

Looking for bipolarity in antidepressant discontinuation manic states: Update and diagnostic considerations of the phenomenon

BACKGROUND

Antidepressant withdrawal manic states are intriguing and under-recognized phenomena. The associated patho-physiological pathways are ill defined and the inclusion of the phenomena in the bipolar spectrum disorders is questionable. This study aims to update a review on antidepressant discontinuation manic states published in 2008 and to look for hints alluding to bipolar disorder in the affected published cases and in the literature. It also reviews the different hypotheses proposed to explain discontinuation mania.

METHODS

We searched Pubmed using the key words: 'antidepressant withdrawal' or 'antidepressant discontinuation' plus 'mania' or 'hypomania' from January 2008 until January 2018.

RESULTS

Five new eligible reports were identified since the last review in 2008, involving the antidepressants Amitriptyline, Fluoxetine, Escitalopram and Mirtazapine. Hypotheses involve the implication of Catecholamines, Acetylcholine and Serotonin in the pathophysiology of this paradoxical phenomenon. Careful analysis of the total 29 cases revealed psychiatric histories in favor of a bipolar spectrum disorder in 12 individuals while five were already known to have bipolar disorder.

LIMITATIONS

This review is based on case reports with associated recall bias, and lack of in-depth description at times.

CONCLUSIONS

Antidepressant discontinuation manic or hypomanic states do not occur randomly. An individual susceptibility to bipolar disorder must be considered.

Antidepressant discontinuation manic states: a critical review of the literature and suggested diagnostic criteria

We critically appraised all published reports of hypomania and mania following antidepressant termination. To increase reliability and validity we devised diagnostic criteria for an antidepressant discontinuation or withdrawal 'manic state' based primarily on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition substance withdrawal criteria. A systematic literature review identified 24 reports meeting our criteria. Mean age was 39 years (range 18-74), men and women were approximately equally represented, and more cases involved people with unipolar (n = 19) than bipolar disorder (n = 4). The median duration of preceding antidepressant treatment was 12 weeks (range 4 weeks-12 years). All major antidepressant classes were involved (tricyclic antidepressants = 13; selective serotonin reuptake inhibitors = 5; monoamine oxidase inhibitors = 3; selective serotonin-norepinephrine reuptake inhibitors = 2; miscellaneous = 1). More cases followed abrupt antidepressant withdrawal (n = 11) than a tapered withdrawal (n = 6). Six cases appeared to meet the criteria of the Diagnostic and Statistical Manual of Mental Disorders, 4th edition for a manic episode, with two cases requiring inpatient admission. Of the 24 cases, nine resolved spontaneously without treatment (median duration = 25.5 days), six responded to antimanic drugs, four resolved following antidepressant reinstatement, and treatment was unclear in five cases. We conclude that antidepressant discontinuation hypomania/mania is a valid syndrome. It should be added to the differential diagnosis of hypomania/mania. The clinical implications and possible mechanisms are discussed.

Pharmacologic mood destabilization: case vignettes

Bipolar disorder is an illness characterized by inherent mood instability that produces a predisposition to depressive, hypomanic, or manic episodes. This predisposition to affective episodes, rather than the episodes themselves (which can have many causes), is arguably the hallmark of bipolar disorder.

Most episodes of bipolar disorder, including the first episode, are depressive. This exposes an inherent flaw in our nosological system, which requires a manic or hypomanic episode for diagnosis of bipolar disorder. Treatment of a depressive episode in undiagnosed bipolar disorder can entail the use of medications that were developed to treat a different disorder (major depressive illness) and that may have mood-destabilizing or activating properties.

Antidepressant-induced mania: an overview of current controversies

OBJECTIVE

The prevalence, characteristics, and possible risk factors associated with antidepressant-induced mania remain poorly described. The present review sought to identify published rates of antidepressant-induced mania and describe risk factors for its emergence.

METHODS

A MedLine search was conducted of journals that focused on mania or hypomania associated with recent antidepressant use. Data from published reports were augmented with relevant findings from recent clinical trials presented at scientific conferences.

RESULTS

Antidepressant-induced manias have been reported with all major antidepressant classes in a subgroup of about 20-40% of bipolar patients. Lithium may confer better protection against this outcome when compared with other standard mood stabilizers, although switch rates have been reported with comparable frequencies on or off mood stabilizers. Evidence across studies most consistently supports an elevated risk in patients with (i) previous antidepressant-induced manias, (ii) a bipolar family history, and (iii) exposure to multiple antidepressant trials.

CONCLUSION

About one-quarter to one-third of bipolar patients may be inherently susceptible to antidepressant-induced manias. Bipolar patients with a strong genetic loading for bipolar illness whose initial illness begins in adolescence or young adulthood may be especially at risk. Further efforts are needed to better identify high-vulnerability subgroups and differentiate illness-specific from medication-specific factors in mood destabilization.

Switch to mania upon discontinuation of antidepressants in patients with mood disorders: a review of the literature

OBJECTIVE

To review the literature for reported cases of mania related to discontinuing antidepressant treatment, as well as for possible explanations of this phenomenon, and to present a case report.

METHOD

We undertook a literature review through the PubMed index, using the key words mania, antidepressant withdrawal, and antidepressants in bipolar disorder. We reviewed 11 articles featuring 23 cases. Where available, we noted and tabulated certain parameters for both bipolar disorder (BD) and unipolar depression. We use a case example to illustrate the phenomenon of mania induced by antidepressant withdrawal.

RESULTS

For patients with unipolar depression, we found 17 reported cases of mania induced by antidepressant withdrawal. Antidepressants implicated included tricyclic antidepressants (TCAs) (12/17), monoamine oxidase inhibitors (MAOIs) (2/17), trazodone (1/17), mirtazapine (1/17), and paroxetine (1/17). For patients with BD, we found 19 reported cases of mania induced by antidepressant withdrawal, including our own case example. Of these, selective serotonin reuptake inhibitors (SSRIs) (10/19), TCAs (4/19), MAOIs (2/19), and serotonin norepinephrine reuptake inhibitors (SNRIs) (2/19) were implicated.

CONCLUSION

Our case report supports the observation of antidepressant withdrawal-induced mania in patients with BD. It is distinguishable from antidepressant-induced mania, physiological drug withdrawal, and mania as a natural course of the illness. Many theories have been put forward to explain this occurrence. Noradrenergic hyperactivity and "withdrawal-induced cholinergic overdrive and the cholinergic-monoaminergic system" are the 2 most investigated and supported models. The former is limited by poor clinical correlation and the latter by its applicability only to anticholinergic drugs.

Pharmacotherapy of depression and mixed states in bipolar disorder

The treatment of bipolar depression requires the resolution of depression and the establishment of mood stability. A basic problem is that the treatments used in treating bipolar depression were developed and proven effective for other disease states: antidepressants for unipolar depression, and mood stabilizers for mania. The panel addressed four unresolved questions regarding depression in relation to bipolar disorder: (1) the relative effectiveness of different antidepressant treatments; (2) the relative likelihood of mood destabilization with different antidepressant treatments; (3) the effectiveness and role of mood-stabilizing medicines as antidepressants; and (4) the optimal approach to mixed states. The selection of an antidepressant depends both on its relative lack of mania- or hypomania-provoking potential and on its effectiveness against bipolar depression. There is little definitive evidence distinguishing effectiveness of the major groups of antidepressive agents, so side-effect profiles and pharmacokinetics are major considerations. The underlying bipolar disorder should be treated with mood stabilizers started simultaneously with any antidepressive treatments. Lithium, divalproex sodium and carbamazepine have all been found to be helpful, to some extent, in treating bipolar depressive episodes as well as for long-term mood stabilization. There is little evidence for long-term benefits of antidepressive agents in bipolar disorder, and some evidence that they may destabilize the disorder. Therefore, in contrast to the long-term use of mood-stabilizers, antidepressant use is recommended on a temporary basis. The duration of antidepressant treatment is determined by past history in terms of liability for mood destabilization, and by the ability of the patient to tolerate gradual antidepressant discontinuation without return of depression. Mixed states, where symptoms of depression and mania coexist, are regarded as a predictor of relatively poor response to lithium, and divalproex has been found to be more effective. Carbamazepine may too be useful in mixed states. Most patients with mixed states in actual practice require combinations of mood stabilizers, though there is little controlled data regarding such co-prescription, especially from a long-term perspective.

Rapid-cycling bipolar disorder. An overview of research and clinical experience

Although many studies of RCBD have been reported over the last 2 decades, knowledge remains limited. Higher incidence in women is the sole clearly replicated finding in most studies. This finding might be mediated by cyclothymia, a temperament that is of higher prevalence in women and that might be considered as a normal variant of RC. Many questions remain unanswered. Review of putative risk factors, such as hypothyroidism and treatment with antidepressants, provides no conclusive answers. There is clinical evidence to implicate both factors. In principle, the thyroid connection can be approached rationally, yet there seems to be no relationship between thyroid status and response to thyroid augmentation. For this reason and given the potential risks of long-term thyroid use, this strategy should not be the first one to be tried in RC. Cumulatively, naturalistic studies over the past 30 years have strongly implicated antidepressants in switching and cycle acceleration, yet the double-blind, controlled, prospective studies that are needed to provide definitive answers are unlikely to be conducted for ethical reasons discussed in this article. Bipolar family history of RC probands appears indistinguishable from non-RC probands, indicating that most likely RCBD does not breed true. Although RC seems to be more lithium resistant with less likelihood of being symptom-free after 2 to 5 years of follow-up, many of these patients nonetheless have resolution of the RC course. There is no marked difference in suicide rates. An association of RC with bipolar type II, D-M-I pattern and those who switch into mania or hypomania on antidepressants is a provocative possibility: Antidepressants might introduce RC by first inducing a switch during a depressive episode, creating a D-M-I pattern, a pattern that is poorly responsive to lithium, which eventually degenerates into RC. Again, this sequence might be mediated by the high prevalence of cyclothymia in bipolar II patients. Thus, data from phenomenology, family history, and long-term outcome do not support RC as a separate entity. RC appears to be a temporary complicated phase in the illness, not a stable feature. This was noted by Kraepelin: I think I am convinced that that kind of classification must of necessity wreck on the irregularity of the disease. The kind and duration of the attacks and the intervals by no means remain the same in the individual case but may frequently change, so that the case must be reckoned always to new forms. Data by Gottschalk et al testify to the chaotic mood swings of contemporary bipolar disorder. Moreover RC is seen in other medical diseases, such as epilepsy, in which patients have phases of increase in frequency of episodes (seizures) that become refractory to treatment. Further longitudinal prospective studies are required to understand the complexity of this intriguing phenomenon and to provide better treatments. Algorithms deriving from tertiary research or university-based clinical experience may not generalize to RC or otherwise treatment-resistant bipolar patients seen in more routine practice. Illness severity in RCBD generally precludes double-blind controlled investigations. Meanwhile, clinicians may rely on discontinuing antidepressants, maintaining patients on combined mood stabilizers--of which valproate is probably the most useful--and making judicious use of atypical neuroleptics. Benzodiazepines and alcohol (which produce withdrawal), caffeine, stimulants, exposure to bright light, and sleep deprivation during excited phases should be avoided. Thyroid and nimodipine augmentation can be considered in those with the most malignant course. These are patients who need the maximal support that their psychiatrist can provide them. Office visits must be arranged as the last appointment of the day.

Administration of antidepressants, diazepam and psychomotor stimulants further confirms the utility of Flinders Sensitive Line rats as an animal model of depression

Flinders Sensitive Line (FSL) rats have been proposed as an animal model of depression because they resemble depressed humans in that they have elevated REM sleep, reduced activity, and increased immobility and anhedonia after exposure to stressors. The present paper reviews experiments on the drug treatment of FSL and control Flinders Resistant Line (FRL) rats related to their utility as an animal model of depression, and presents new information. FSL rats exhibited exaggerated immobility in the forced swim test which is counteracted by the tricyclic antidepressants imipramine and desipramine and the serotonin reuptake blocker sertraline; the low immobility exhibited by the FRL rats is generally unaffected by these compounds. In contrast to these "therapeutic" effects of well recognized antidepressants, lithium and bright light treatment did not alter the exaggerated immobility of FSL rats. Novel data indicated that neither FSL nor FRL rats exhibited alterations in swim test immobility following chronic administration of the psychomotor stimulant amphetamine (2 mg/kg) and the anticholinergic scopolamine (2 mg/kg), which typically reduce immobility after acute administration. However, it was found that the calcium channel blockers verapamil (5 and 15 mg/kg) and nicardipine (10 mg/kg) did reduce the exaggerated immobility in FSL rats following chronic administration, suggesting that these compounds need to be evaluated further in humans. Previous studies have indicated no differences between FSL and FRL rats evaluated in the elevated plus maze, either at baseline or after the administration of diazepam, suggesting that the FSL rat may not differ from controls in anxiety-related behavior. Another recently published study showed that the FSL rat also did not differ from normal Sprague-Dawley rats in startle tests, indicating that the FSL rats do not exhibit behaviors shown in animal models of schizophrenia. These findings confirm the utility of FSL rats as an animal model of depression because the FSL rats do not appear to exhibit behaviors analogous to anxiety or schizophrenia and because they respond "therapeutically" to antidepressants and not psychomotor stimulants.

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.

Pyridostigmine-induced growth hormone responses in healthy and depressed subjects: evidence for cholinergic supersensitivity in depression

Theorists have extrapolated the cholinergic supersensitivity theory of affective disorder from a convincing and broad spectrum of clinical observation and research. This hypothesis is tested using a neuroendocrine probe approach with the challenge drug pyridostigmine, an indirect cholinergic agent thought to release growth hormone (GH) by decreasing inhibitory somatostatin tone. The consequent increments in plasma GH were considered to reflect central acetylcholine responsivity. Fifty-four volunteers were tested: 27 DSM-III-R major depressives (18 women and 9 men) and 27 age- and sex-matched healthy controls. Subjects were cannulated at 9.00 h following an overnight fast and two baseline samples were taken at 15 min intervals. Pyridostigmine 120 mg was administered orally and thereafter samples were taken at the time points +60, +90, +120 and +180 min. GH responses were significantly greater in depressives than controls and this effect was more marked for men than women. These results support the proposal that muscarinic upregulation and/or supersensitivity is associated with depression.

Clinical and biochemical aspects of depressive disorders: II. Transmitter/receptor theories

The present document is the second of three parts in a review that focuses on recent data from clinical and animal research concerning the biochemical bases of depressive disorders, diagnosis, and treatment. Various receptor/transmitter theories of depressive disorders are discussed in this section. Specifically, data supporting noradrenergic, serotonergic, cholinergic, dopaminergic, GABAergic, and peptidergic theories, as well as interactions between noradrenergic and serotonergic, or cholinergic and catecholaminergic systems are presented. Problems with the data and future directions for research are also discussed. A previous publication, Part I of this review, dealt with the classification of depressive disorders and research techniques for studying the biochemical mechanisms of these disorders. A future publication, Part III of this review, discusses treatments for depression and some of the controversies in this field.

Sleep-loss as a possible mediator of diverse causes of mania

When sleep duration and mood were monitored longitudinally in a 59-year-old woman with bipolar illness, sleep loss appeared to mediate the triggering of mania by psychosocial and pharmacological precipitating factors. This interpretation was supported by observations that mania could repeatedly be induced experimentally by depriving her of sleep for one night. The patient's data illustrate how sleep-loss might be a preventable cause of mania in a variety of situations.

Bright light blocks the capacity of inescapable swim stress to supersensitize a central muscarinic mechanism

Clinical and basic researchers have proposed that muscarinic cholinergic mechanisms mediate some effects of chronic stress. Chronic inescapable (forced) swim stress depletes brain biogenic amines and is used to produce learned helplessness in rats. Behavioral and biochemical characteristics of animals in the state of learned helplessness lead some investigators to believe this condition provides a useful animal model of depression. Inescapable swim stress also produces supersensitivity to the hypothermic effect of the muscarinic agonist oxotremorine in the rat. The authors previously demonstrated that bright light potently induces subsensitivity of a central muscarinic mechanism involved in the regulation of core temperature under a variety of circumstances. They now report using a repeated measures design that inescapable swim stress of five days duration produces supersensitivity to oxotremorine (increase in thermic response of 405%). This supersensitivity is reversed within five days by treatment with bright light, despite continuation of daily swim stress. Daily inescapable swim stress was continued beyond cessation of treatment with bright light. Five days later, supersensitivity to the hypothermic effect of oxotremorine was once again evident.

Heterocyclic antidepressant, monoamine oxidase inhibitor and neuroleptic withdrawal phenomena

1. The authors review the literature describing acute symptomatology produced by the gradual or abrupt withdrawal of heterocyclic antidepressants, monoamine oxidase inhibitors (MAOI) and neuroleptics. 2. Withdrawal of heterocyclic antidepressants and antipsychotic agents causes similar symptomatology. Symptoms produced by the discontinuation of these drugs include nausea, emesis, anorexia, diarrhea, rhinorrhea, diaphoresis, myalgias, paresthesias, anxiety, agitation, restlessness, and insomnia. 3. Psychotic relapse is often presaged by anxiety, agitation, restlessness, and insomnia. Prodromal symptoms are distinguished from the effects of neuroleptic withdrawal by a temporal relationship of the latter to reductions in the dosage or discontinuation of antipsychotic agents. 4. Withdrawal of MAOIs can result in severe anxiety, agitation, pressured speech, sleeplessness or drowsiness, hallucinations, delirium, and paranoid psychosis. 5. MAOI withdrawal phenomena resemble the symptoms produced by the discontinuation of chronically administered psychostimulants. 6. The capacity of MAOIs to exert amphetamine-like effects presynaptically and the propensity of somatic treatments for depression to subsensitize presynaptic receptors regulating the release of catecholamines provide a basis for the development of psychotic symptoms upon the withdrawal of MAOI. Evidence for this hypothesis is reviewed.

Antidepressant effects of rolipram in a genetic animal model of depression: cholinergic supersensitivity and weight gain

The effects of rolipram, a new generation antidepressant which is a selective inhibitor of phosphodiesterase, on the selectively bred Flinders Sensitive Line (FSL) of rats, a genetic animal model of depression, was studied. Acutely, rolipram produced comparable decreases in temperature and activity in the FSL and the Flinders Resistant Line (FRL) rats. Upon chronic treatment there was a trend for rolipram to counteract the shock-induced suppression of activity in the FSL rats, suggesting an antidepressant-like effect. However, both groups gained a significant amount of weight, which appeared to be associated with polydipsia and polyuria. In addition, both groups were significantly more affected by the muscarinic agonist, oxotremorine, than their vehicle-treated counterparts. Thus, the FSL rats, which are genetically supersensitive to cholinergic agonists, are even more sensitive following chronic treatment with rolipram. These unexpected findings suggest that rolipram may not be appropriate as an antidepressant for humans because of undesirable side effects.

Drug-induced mania--causative agents, clinical characteristics and management. A retrospective analysis of the literature

128 case reports of drug-induced mania were reviewed. Steroids, levodopa and other dopaminergic agents, iproniazid, sympathomimetic amines, triazolobenzodiazepines and hallucinogens were the agents that most commonly induced manic syndromes. The most common characteristics of drug-induced manic episodes were increased activity, rapid speech, elevated mood, and insomnia. Patients who developed mania often had a prior history, family history, or current symptoms of mood disturbance. The episodes were most commonly treated by discontinuing or reducing the dose of causative agent. Discontinuation of the inciting drug and treatment with neuroleptic agents were equally efficacious: lithium treatment was less effective. The majority of agents that induce mania have an effect on monoaminergic systems.

Pharmacologic perturbation strategies in the study of the neurobiology of depression

1. Psychological, behavioral, physiological, biochemical, and receptor binding measurements are useful as dependent variables when studying the biology of depression and mania. 2. Pharmacological perturbations of cholinergic mechanisms can produce changes mimicking aspects of the neurobiology of affective disorders. 3. These changes can be quantitated by measuring their impact on variables in each of these classes. 4. Pharmacological methods for inducing these changes in cholinergic systems and their application to clinical and basic research in the field of affective disorders are highlighted.

Implications of perturbation strategies: a philosopher of science's perspective

Shifts in the classification of multiple variables can contribute to change in psychiatry's concept of a disorder. These shifts or transitions can occur as a consequence of the expansion of knowledge. A concomitant change in the literal form of diagnostic labels is not required. For example, the definitions of "mass" within the framework of Newtonian and Einsteinian theories are conceptually incompatible even though the same label is used to denote both concepts. Implications of the principles discussed for theory and practice in psychiatry are emphasized.

Biology of depression

Research over the past three decades has led to a greater understanding of the biologic basis of depression. Observations that certain medications could improve or worsen mood led to the development of hypotheses describing the possible role of specific neurotransmitters in the brain in depression. Modifications of these original hypotheses focused on altered receptor function, failures in the regulation of neurotransmitter systems, and interactions of the monoamines with cholinergic systems. Strategies using endocrinologic measurements in the evaluation of the depressed patient have provided researchers with new clues regarding disordered neuroendocrine function in depression and clinicians with new tests to aid in diagnosis and management. Moreover, the development of standardized sleep EEG methodology has proven useful for the identification of characteristic sleep abnormalities in depression. Although there are many methodologic and clinical problems still to be resolved, the use of biological markers in the assessment of the depressed patient is increasing, and is likely to be of significant importance in the future. Finally, recent advances in molecular genetics hold promise for further advances in our understanding of the inheritance and biochemistry of depression.

Monoamine oxidase inhibitor withdrawal phenomena: symptoms and pathophysiology

The author reviews the literature reporting the untoward effects of withdrawing monoamine oxidase inhibitors (MAOIs). The withdrawal of these agents can result in severe anxiety, agitation, pressured speech, sleeplessness or drowsiness, hallucinations, delirium and paranoid psychosis. MAOI withdrawal phenomena resemble the symptoms produced by the discontinuation of chronically administered psychostimulants. The capacity of MAOI to exert amphetamine-like effects presynaptically, and the propensity of somatic treatments for depression to subsensitize presynaptic receptors regulating the release of catecholamines, can provide a basis for the development of psychotic syndromes upon the withdrawal of MAOIs. Evidence for this hypothesis is reviewed.

Withdrawal symptoms from phenytoin, carbamazepine and sodium valproate

A prospective, double-blind, placebo-controlled investigation of possible withdrawal symptoms from phenytoin, carbamazepine and sodium valproate is reported in patients with active epilepsy, on combination therapy. There was an increase in seizures on reduction and withdrawal of carbamazepine, but there was no convincing evidence of withdrawal symptoms from any of these drugs.

Genetic and pharmacological models of cholinergic supersensitivity and affective disorders

Increased muscarinic sensitivity has been associated with altered hormonal states (hypothyroidism and hyperadrenocorticism), chronic administration of muscarinic antagonists or antidepressants with muscarinic actions, selective breeding for anticholinesterase sensitivity, and certain inbred strains of rats and mice. Thus, both genetic and environmental factors may influence muscarinic receptor sensitivity. The reasonably detailed studies on the selectively-bred rats have revealed that the Flinders Sensitive Line (FSL) rats weigh less, are less active, are more sensitive to muscarinic agonists and to stressors, and have higher concentrations of hippocampal and striatal muscarinic receptors than 'normal', or the selectively-bred, Flinders Resistant Line (FRL) rats. Thus, there are a number of parallels between FSL rats and depressed humans. The FSL rats may be the first animal model of depression to mimic the actual trait of depression, and not just the state.

Effects of stress on muscarinic mechanisms

Hyperactivity of muscarinic mechanisms may be involved in the patho-physiology of depressive disorders and stress. The literature emphasizes the impact of stress on aminergic networks and muscarinic mechanisms are generally not accorded a significant role in the neurobiology of stress. However, experiments in man and animals indicate that acute and chronic stress activate central muscarinic mechanisms. The literature reporting these results is reviewed.

Temperature as a dependent variable in the study of cholinergic mechanisms

1. Change in core temperature over time can be used as a dependent variable when studying the effects of manipulations on neurotransmitter systems. This article focuses on the measurement of core temperature as a strategy for detecting changes in the status of cholinergic systems. 2. Cholinergic neurons participate in the process of thermoregulation and interventions affecting them alter the thermal response to cholinomimetics. For example, chronic treatment with amitriptyline, chronic swim stress and inescapable footshock supersensitize rats to the hypothermic effects of oxotremorine. 3. This is consistent with the hypothesis that the pathophysiologies of tricyclic antidepressant withdrawal phenomena and stress involve supersensitivity of muscarinic mechanisms. 4. Uses of thermoregulation paradigms for investigating the actions of lithium ion, electroconvulsive shock and substances of abuse on muscarinic mechanisms are discussed. Applications to problems in the arena of clinical research are highlighted.

[Current hypotheses on the mechanism of action of lithium]

This article aims to clarify and organize the recent advances in research on the central action mechanism of lithium. It begins by tackling the process of cellular transport of the cation, then it moves on to describe the effects of lithium on ionic distribution and on membranous functioning in general. Neurotransmission in this article is the object of a more detailed study. The metabolism of neurotransmitters (and their disturbances) is first discussed. The emphasis is placed on certain current domains, the gabaergic system in particular. Neurotransmitters, by themselves, do not satisfy any longer the curiosity of biologists. Technological progress has given these scientists access to the intimate functioning of receptors and to their natural support system, the membrane. The stabilizing effect of lithium is mentioned often. Initially seen at a superficial level, it leads to a study of the mechanisms of the transference of information from the receptor to the cell. The membranous phospholipids and the enzymatic systems controlling the metabolism of the second messengers (cyclic nucleotides but also calcium) will provide as many potential targets to the action of lithium.

Cholinergic properties of desipramine and amoxapine: assessment using a thermoregulation paradigm

1. The withdrawal of tricyclic antidepressants (TCAs) produces symptoms suggesting cholinergic rebound. 2. Amitriptyline (AMI), the most potent antimuscarinic agent among this class of drugs, produces supersensitivity to the muscarinic agonist, oxotremorine. 3. Enhancement of the sensitivity of cholinoceptive neurons to acetylcholine as a consequence of treatment with TCAs would account for many of the symptoms following the withdrawal of these drugs. 4. Desipramine (DMI) is the least potent antimuscarinic compound among the TCAs, yet its withdrawal produces withdrawal symptoms. 5. Recently, it was reported that amoxapine (AMX) weakly binds to muscarinic acetylcholine receptors (mAchR) in vitro. This may indicate that this drug lacks the effects antimuscarinic effects in vivo, and that it will not supersensitize cholinergic networks. 6. A thermoregulation paradigm was used to assess the sensitivity of a central muscarinic mechanism to oxotremorine before and after treatment with DMI and AMX. Treatment with either drug increased the hypothermic response to this agonist. 7. Mechanisms whereby drugs can produce cholinergic system supersensitivity, and the use of thermoregulation paradigms in assessing the properties of therapeutic agents is discussed.

Rhythm and blues. Neurochemical, neuropharmacological and neuropsychological implications of a hypothesis of circadian rhythm dysfunction in the affective disorders

Current views on the organisation and functions of the circadian rhythm system are outlined. Evidence is presented supportive of the notion that the pathophysiology of the affective disorders involves a disruption of circadian rhythms and that the primary locus of action of agents effective in the affective disorders is on the circadian rhythm system. Potential disruptions of this system are enumerated. Such a hypothesis, it is argued, might potentially unite the disparate neurochemical and neuroendocrinological findings emerging in both depression and mania. There are in addition neuropsychological and nosological implications of such a framework, which may help bridge the divide between molecular and behavioural approaches to research on the affective disorders which are outlined.

Cholinergic mechanisms in affective disorders. Future directions for investigation

Advances in clinical and basic research methodology combined with clearly articulated concepts create new opportunities for researching the roles of cholinergic mechanisms in the pathophysiology of affective disorders. Areas for study include: roles of cholinergic mechanisms in mediating effects of stress and cholinergic mechanisms linking the pathophysiologies of affective and panic disorders, use of pharmacologic agents to produce cholinergic system supersensitivity in modeling biologic aspects of affective illness, use of multigenerational intrapedigree studies of cholinergic markers associated with affective disease, research into the neurobiology of lithium and ECT as they pertain to muscarinic cholinergic mechanisms, study of the interrelationship of sodium, calcium and lithium ion metabolism and their relationship to cholinergic-monoaminergic interaction, the development of brain imaging strategies and techniques, e.g., positron emission tomography (PET), to measure changes in cholinergic receptor density and affinity as a function of clinical state, identification and validation of a peripheral model of the central muscarinic receptor, study of the pharmacology of abusable substances and its relationship to mechanisms regulating mood, affect, psychomotor function and other variables related to the affective disorders, and development of in vitro and in vivo models useful in studying the physiology and biochemistry of the interaction of cholinergic and monoaminergic neurons. These models may allow us to bridge the traditional cholinergic and monoamine hypotheses of affective disorders.

Cholinergic mechanisms in depression

Evidence supporting a cholinergic hypothesis of depression is presented. First, cholinergic overdrive produces behavioral, neuroendocrine, and polysomnographic features of melancholia, and melancholics exhibit state-independent supersensitivity to cholinergic overdrive. Drugs inducing up-regulation and supersensitivity of cholinergic systems produce behavioral, polysomnographic, and neuroendocrine effects of melancholia when withdrawn. These observations also implicate cholinergic system supersensitivity as a factor in the pathophysiology of certain affective disorders. Cholinergic and monoaminergic mechanisms reciprocally regulate drive-reduction, and substances of abuse either activate monoaminergic networks or antagonize cholinergic systems. These points are consistent with the hypothesis that dynamic interaction between cholinergic and monoaminergic systems is involved in the regulation of mood and affect. Finally, antimuscarinic agents have antidepressant effects. Thus, the hypothesis that supersensitivity of cholinergic systems is involved in the pathophysiology of affective disorders is supported by several lines of evidence. This evidence is reviewed; directions for future research and promising methods of investigation are discussed.

Covariation of depressive symptoms, parkinsonism, and post-dexamethasone plasma cortisol levels in a bipolar patient: simultaneous response to ECT and lithium carbonate

A patient presented with concurrent mood congruent delusions, parkinsonism, and elevated post-dexamethasone plasma cortisol levels. This triad could result from simultaneous development of cholinergic-monoaminergic dysfunction within critical limbic and extrapyramidal loci. The magnitude of each abnormality decreased in concert during a course of electroconvulsive therapy (ECT). Remaining abnormalities disappeared during treatment with lithium. Actions of ECT and lithium on muscarinic systems are reviewed, and a strategy for testing the hypothesis that dysfunction of cholinergic-monoaminergic mechanisms develops in parallel in different neural networks is considered.

Stress-induced immobility in rats with cholinergic supersensitivity

Immobility during forced swimming or after mild footshock (1 mA for 2 sec) was observed in five groups of rats. The Flinders Sensitive Line (FSL) of rats, known to be more sensitive to cholinergic agonists, exhibited the greatest degree of immobility in the forced swim test. Rats chronically treated with, and subsequently withdrawn from, either scopolamine (2 mg/kg, once daily) or amitriptyline (10 mg/kg, once daily) were also significantly more immobile than either a control group treated chronically with isotonic saline or the Flinders Resistant Line (FRL) of rats in the forced swim test. Similar trends were observed for locomotor depression in the open field following exposure to footshock. Receptor binding studies indicated significantly greater concentrations of muscarinic acetylcholine receptors in the hippocampus of the scopolamine, and amitriptyline, withdrawn rats. These findings indicate that rats with increased cholinergic sensitivity are more sensitive to the immobility-inducing effects of mild stressors. Thus, they may prove to be useful models for studying the relationship between affective disorders and the cholinergic system.

Effects of antidepressant withdrawal on the dexamethasone suppression test

Withdrawal of antidepressant medications may be a source of variance in dexamethasone suppression test (DST) results. We investigated this issue retrospectively through the serial analysis of postdexamethasone plasma cortisol concentrations and clinical severity in 15 patients and 9 control subjects before, during, and after antidepressant withdrawal. Postdexamethasone cortisol concentrations were significantly higher during the antidepressant withdrawal phase. Drug-withdrawal subjects also had an increased frequency of DST nonsuppression. Recent withdrawal of antidepressants requires further study as a possible source of variance for hypothalamic-pituitary-adrenal measures.