Effects of subchronic treatment with valproate on L-5-HTP-induced cortisol responses in mania: evidence for increased central serotonergic neurotransmission

Is Poor Lithium Response in Individuals with Bipolar Disorder Associated with Increased Degradation of Tryptophan along the Kynurenine Pathway? Results of an Exploratory Study

Bipolar disorder is associated with an inflammation-triggered elevated catabolism of tryptophan to the kynurenine pathway, which impacts psychiatric symptoms and outcomes. The data indicate that lithium exerts anti-inflammatory effects by inhibiting indoleamine-2,3-dioxygenase (IDO)-1 activity. This exploratory study aimed to investigate the tryptophan catabolism in individuals with bipolar disorder (n = 48) compared to healthy controls (n = 48), and the associations with the response to mood stabilizers such as lithium, valproate, or lamotrigine rated with the Retrospective Assessment of the Lithium Response Phenotype Scale (or the Alda scale). The results demonstrate an association of a poorer response to lithium with higher levels of kynurenine, kynurenine/tryptophan ratio as a proxy for IDO-1 activity, as well as quinolinic acid, which, overall, indicates a pro-inflammatory state with a higher degradation of tryptophan towards the neurotoxic branch. The treatment response to valproate and lamotrigine was not associated with the levels of the tryptophan metabolites. These findings support the anti-inflammatory properties of lithium. Furthermore, since quinolinic acid has neurotoxic features via the glutamatergic pathway, they also strengthen the assumption that the clinical drug response might be associated with biochemical processes. The relationship between the lithium response and the measurements of the tryptophan to the kynurenine pathway is of clinical relevance and may potentially bring advantages towards a personalized medicine approach to bipolar disorder that allows for the selection of the most effective mood-stabilizing drug.

Antiepileptic drugs and serotonin syndrome- A systematic review of case series and case reports

Serotonin syndrome (SS) is a drug‑induced, potentially fatal, clinical syndrome resulting from drugs that have serotonergic properties. Several antiepileptic drugs (AEDs) are known to have serotonergic properties and it can be hypothesized that such AEDs can cause SS. This study aims to review the literature on SS in patients receiving AEDs. We performed a systematic review of Scopus and MEDLINE/PUBMED for case reports and case series of SS where patients had received at least one AED at the onset of symptoms. The cases published in the English literature between 1 January 1991 and 1 April 2021 were included. Initial search identified 1263 articles of which 63 (76 patients) were included in the final analysis. Most of the included cases (53 cases, 70%) have been published in the last 10 years. The mean age of the 76 patients was 40.6 ± 17.8 years, and 51% of cases were females. These patients had been exposed to a total of 8 different types of AEDs. Valproic acid was the most common drug (29, 38%), followed by lamotrigine (22, 29%), gabapentin (16, 21%), pregabalin (seven, 9%), topiramate (five, 7%) and carbamazepine (two, 3%). There has been one case each with phenytoin and oxcarbazepine. Seven (9%) patients received more than one AEDs. Most patients (67, 88%) also received other serotoninergic agents. Only nine (12%) patients were on AEDs alone. The most common clinical condition for using AEDs was psychiatric disorders (36 patients, 47.3%), followed by migraine (17, 22.4%), other painful conditions (15, 19.7%), epilepsy (7, 9.2%), and perioperative conditions (8, 10.5%). Death was reported in two patients. We suggest that AEDs, because of their serotonergic properties, may induce SS, especially in patients who are on another serotonergic agent.

The Therapeutic Effects of Low-Frequency Electrical Stimulations Adjunct to Sodium Valproate on Seizure and Behaviors

Introduction:

Consuming antidepressant medications induce several problems leading to the need for alternative agents for emotional disturbances. Antidepressant medications increase the seizure risk; thus, alternative treatments, like Antiepileptic Drugs (AED), might be useful for patients with epilepsy comorbid with a psychiatric disorder. The present study evaluated the behavioral effects of sodium valproate, a none effective dose in seizure treatment [100 mg/kg; Intraperitoneal (IP)] along with the application of Low-Frequency Stimulations (LFS) during CA1 hippocampal kindling.

Methods:

In total, 42 male rats were randomly divided into 6 groups, including control group with intact animals handled daily (I); sham group which was subjected to the surgical process, but received no real stimulation (II); saline-kindled Kindled group (S.kindled) which were stimulated daily with the following protocol: 3 strain of 50Hz monophasic pulses of 1ms duration applied 12 times a day with the threshold intensity at intervals of 10 minutes where saline was administrated 15 min before kindling stimulations (III); saline-kindled-LFS group (K4LFS) in which saline was injected 15 min before kindling stimulations and LFS was applied daily after the termination of kindling stimulation (IV); drug-kindle group (Drug100.kindled) that underwent rapid kindling procedure daily where sodium valproate (100 mg/kg) was administrated 15 min before kindling stimulations(V), and drug-kindled-LFS (Drug100.kindled.4LFS) group in which drug and LFS were administrated respectively before and after kindling stimulations (VI). The behavioral tests were assessed using elevated plus maze, open field, and forced swim tests.

Results:

The combination of sodium valproate (100 mg/kg) and LFS significantly decreased cumulative seizure severity compared with the kindle group. Thus, it provided a strong seizure suppressing effect. Additionally, sodium valproate and LFS increased the percentage of Open Arms (OAs) entries and the OAs exploration; they also decreased jumping from elevated plus maze test and rearing in open field test. Furthermore, there was no significant change in the OAs entries and OAs exploration percentages, jumping from apparatus, and rearing in open field in Drug100. Kindled, K4LFS, and Drug100.kindled.LFS groups, compared with the sham group. There was no significant difference in the latency to first immobility and the duration of immobility in K4LFS groups compared with the S. kindled group. In the drug-kindled group, the latency to first immobility significantly increased, and the duration of immobility decreased, compared with the S. kindled group. Besides, the latency to first immobility significantly increased, and the duration of immobility decreased in drug-kindled-LFS, compared to S. kindled group; however, the latency to first immobility was not significantly changed, compared to drug-kindled groups.

Conclusion:

Sodium valproate and LFS can modulate the function of the brain regions involved in emotional processing in epilepsy, as well as anxiety- and depressive-like behaviors. Such a combination could also decrease emotional disturbances induced by the kindling process.

Anticonvulsants as mood stabilisers

Recent research has highlighted the fact that a significant number of patients with bipolar affective disorder have a poor outcome (Cole et al, 1993). The most common poor outcome is the development of rapid or ultra-rapid cycling, but mixed states, prolonged depression and severe mania are also associated with poor outcome. It is estimated that approximately one-third of patients with bipolar affective disorder do not respond fully to lithium and a significant number of patients discontinue lithium (Post, 1990) which may itself cause further problems.

Mood stabilizer treatment increases serotonin type 1A receptor binding in bipolar depression

Abnormal serotonin type 1A (5-HT1A) receptor function and binding have been implicated in the pathophysiology of mood disorders. Preclinical studies have consistently shown that stress decreases the gene expression of 5-HT1A receptors in experimental animals, and that the associated increase in hormone secretion plays a crucial role in mediating this effect. Chronic administration of the mood stabilizers lithium and divalproex (valproate semisodium) reduces glucocorticoid signaling and function in the hippocampus. Lithium has further been shown to enhance 5-HT1A receptor function. To assess whether these effects translate to human subject with bipolar disorder (BD), positron emission tomography (PET) and [18F]trans-4-fluoro-N-(2-[4-(2-methoxyphenyl) piperazino]-ethyl)-N-(2-pyridyl) cyclohexanecarboxamide ([(18)F]FCWAY) were used to acquire PET images of 5-HT1A receptor binding in 10 subjects with BD, before and after treatment with lithium or divalproex. Mean 5-HT1A binding potential (BPP) significantly increased following mood stabilizer treatment, most prominently in the mesiotemporal cortex (hippocampus plus amygdala). When mood state was also controlled for, treatment was associated with increases in BPP in widespread cortical areas. These preliminary findings are consistent with the hypothesis that these mood stabilizers enhance 5-HT1A receptor expression in BD, which may underscore an important component of these agents' mechanism of action.

Immunity, inflammation, and bipolar disorder: diagnostic and therapeutic implications

Bipolar disorder is now known to be associated not only with highly prevalent co-occurring psychiatric and substance use disorders but also with medical comorbidities, such as cardiovascular diseases, diabetes mellitus, obesity and thyroid dysfunction. Inflammatory disturbances repeatedly observed in bipolar disorder, can explain some of the comorbidity between bipolar disorder and medical disorder. This revised perspective of bipolar disorders should promote the development of therapeutic tools. Immuno-inflammatory dysfunction may well represent a significant component of the underlying pathophysiology of the disorder. We therefore propose to review the immuno-inflammatory hypothesis in bipolar disorder considering the co-occurence with autoimmune diseases, immunological and inflammatory markers, as well as immuno-genetic markers which could lead to personalized treatments.

Anticonvulsant drugs in bipolar disorder

Although much progress has been made in successfully treating bipolar disorder, there is increasing awareness of the limitations of traditional treatment regimens such as lithium and neuroleptics. The large family of anticonvulsant drugs, however, appears to be capable of providing new treatment options, not only as medication of second choice in patients refractory to treatment, but often as a treatment standard with high efficacy and low incidence of side effects. Besides established mood stabilizers such as carbamazepine and valproate, new antiepileptic drugs are entering the field with promising initial results in the treatment of bipolar patients. Furthermore, bringing to light the mechanisms of action of anticonvulsants and the similarities between anticonvulsants effective in bipolar disorder may also deepen our understanding of the pathophysiological basis of the disorder.

5-HT(1A) receptor binding in euthymic bipolar patients using positron emission tomography with [carbonyl-(11)C]WAY-100635

BACKGROUND

This study was undertaken to examine whether brain 5-HT(1A) receptor binding is reduced in euthymic bipolar patients.

METHODS

Eight medicated euthymic bipolar patients and 8 healthy volunteers underwent positron emission tomography scanning using the selective 5-HT(1A) receptor radioligand [carbonyl-(11)C]WAY-100635.

RESULTS

No significant difference in global postsynaptic parametric binding potential (BP(ND)) was found between euthymic bipolar patients (mean + or - SD, 4.24 + or - 0.76) and healthy volunteers (mean + or - SD, 4.34 + or - 0.86). Ninety five percent Confidence Intervals for the difference in group mean global postsynaptic BP(ND) were -0.77 to 0.97. Analysis of regional BP(ND) did not reveal regional differences between patients and healthy controls.

LIMITATIONS

The number of subjects studied was limited and all subjects were on medication.

CONCLUSIONS

In contrast to previous findings of reduced 5-HT(1A) receptor binding in untreated unipolar and bipolar depressed patients [Sargent, P.A., Kjaer, K.H., Bench, C.J., Rabiner, E.A., Messa, C., Meyer, J., Gunn, R.N., Grasby, P.M., Cowen, P.J., 2000. Brain serotonin1A receptor binding measured by positron emission tomography with [(11)C]WAY-100635: effects of depression and antidepressant treatment. Arch. Gen. Psychiatry 57, 174-180]; [Drevets, W.C., Frank, E., Price, J.C., Kupfer, D.J., Holt, D., Greer, P.J., Huang, Y., Gautier, C., Mathis, C., 1999. PET imaging of serotonin1A receptor binding in depression. Biol. Psychiatry 46, 1375-1387] and in recovered unipolar depressed patients [Bhagwagar, Z., Rabiner, E.A., Sargent, P.A., Grasby, P.M., Cowen, P.J., 2004. Persistent reduction in brain serotonin1A receptor binding in recovered depressed men measured by positron emission tomography with [(11)C]WAY-100635. Mol. Psychiatry 9, 386-92], this study found no difference in 5-HT(1A) receptor BP(ND) between medicated euthymic bipolar patients and healthy controls. Normal 5-HT(1A) receptor BP(ND) in these patients may be a result of drug treatment or could indicate that reduced 5-HT(1A) receptor binding is specific to the depressed state in bipolar patients.

Anticonvulsants in bipolar disorder

Anticonvulsant drugs are widely used in psychiatric indications. This includes alcohol and benzodiazepine withdrawal symptoms, panic and anxiety disorders, dementia, schizophrenia, and to some extent personality disorders. Besides pain syndromes, their main domain outside epilepsy, however, is bipolar disorder. Carbamazepine, valproate, and lamotrigine are meanwhile recognized mood stabilizers, but several other antiepileptic drugs have also been tried out with diverging or inconclusive results. Understanding the mechanisms of action and identifying similarities between anticonvulsants effective in bipolar disorder may also enhance our understanding of the underlying pathophysiology of the disorder.

The inflammatory & neurodegenerative (I&ND) hypothesis of depression: leads for future research and new drug developments in depression

Despite extensive research, the current theories on serotonergic dysfunctions and cortisol hypersecretion do not provide sufficient explanations for the nature of depression. Rational treatments aimed at causal factors of depression are not available yet. With the currently available antidepressant drugs, which mainly target serotonin, less than two thirds of depressed patients achieve remission. There is now evidence that inflammatory and neurodegenerative (I&ND) processes play an important role in depression and that enhanced neurodegeneration in depression may-at least partly-be caused by inflammatory processes. Multiple inflammatory-cytokines, oxygen radical damage, tryptophan catabolites-and neurodegenerative biomarkers have been established in patients with depression and these findings are corroborated by animal models of depression. A number of vulnerability factors may predispose towards depression by enhancing inflammatory reactions, e.g. lower peptidase activities (dipeptidyl-peptidase IV, DPP IV), lower omega-3 polyunsaturated levels and an increased gut permeability (leaky gut). The cytokine hypothesis considers that external, e.g. psychosocial stressors, and internal stressors, e.g. organic inflammatory disorders or conditions, such as the postpartum period, may trigger depression via inflammatory processes. Most if not all antidepressants have specific anti-inflammatory effects, while restoration of decreased neurogenesis, which may be induced by inflammatory processes, may be related to the therapeutic efficacy of antidepressant treatments. Future research to disentangle the complex etiology of depression calls for a powerful paradigm shift, i.e. by means of a high throughput-high quality screening, including functional genetics and genotyping microarrays; established and novel animal and ex vivo-in vitro models for depression, such as new transgenic mouse models and endophenotype-based animal models, specific cell lines, in vivo and ex vivo electroporation, and organotypic brain slice culture models. This screening will allow to: 1) discover new I&ND biomarkers, both at the level of gene expression and the phenotype; and elucidate the underlying molecular I&ND pathways causing depression; and 2) identify new therapeutic targets in the I&ND pathways; develop new anti-I&ND drugs for these targets; select existing anti-I&ND drugs or substances that could augment the efficacy of antidepressants; and predict therapeutic response by genetic I&ND profiles.

Suicidality and Antiepileptic Drugs

The main purpose of the present article is to review the possible risk factors for suicidal behaviour in epilepsy with a special emphasis on the different antiepileptic drugs (AEDs). Epidemiological data show that, in general, the suicide rate among patients with epilepsy is 5-fold higher than that in the general population, while in temporal lobe epilepsy and complex partial seizures it is approximately 25-fold higher. A certain psychiatric comorbidity may provoke suicidality in patients with epilepsy, and depression and cognitive impairment seem to be the main risk factors for suicidality in epilepsy. In addition, depression and cognitive deterioration in epilepsy may share common neuropsychological mechanisms in terms of hypofrontality. This may cause similar psychopathological signs in both diagnostic categories, including suicidality. Analysis of the literature has shown that serotonin metabolism disturbances are involved in the pathogenesis of suicidal behaviour irrespective of primary diagnosis. Serotonin disturbances also seem to be a common link between depression, suicidality and even epilepsy itself. The various AEDs differ not only in their mechanisms of action, but also in influences on cognition and mood in epileptic patients and suicidality, respectively. Until now, only Ketter's hypothesis has been proposed to explain the psychotropic effects of different AEDs, although it does not explain the positive psychotropic effects of some AEDs, such as carbamazepine and oxcarbazepine. According to this model, all psychotropic effects of AEDs may be the result of effects on the function of two types of receptor functions: gamma-aminobutyric acid (GABA) ergic and antiglutamatergic; other possible mechanisms have not been incorporated. Presumably, other neurochemical mechanisms, and a serotonergic mechanism in particular, should also be taken into account when explaining the psychotropic effects of different AEDs. Based on these data, it has been suggested that AEDs with certain serotonergic properties should reduce the suicidality risk because they exert effects similar to antidepressants (i.e. selective serotonin reuptake inhibitors), whereas AEDs that lack serotonergic mechanisms would not be effective in suicidality prevention. In line with this paradigm, phenobarbital and phenytoin seem to be the only drugs with proven suicidality risk. On the other hand, carbamazepine, oxcarbazepine, valproate and lamotrigine could be regarded as drugs with antisuicidal properties because they all improve cognitive functions and mood in epileptic patients, and possess serotonergic mechanisms of action. The other AEDs, including topiramate, tiagabine, vigabatrin, levetiracetam and zonisamide, all exert negative effects on mood and cognition, although their influence on suicidality has not been proven in evidence-based studies yet. Although zonizamide has serotonergic properties, it exerts negative psychotropic effects, whereas gabapentin is devoid of serotonergic properties but has positive psychotropic effects on mood and cognition. To more fully explain the positive and negative psychotropic effects and influence on suicidality of AEDs, Ketter's paradigm should be supplemented by an understanding of the serotonergic mechanisms of different AEDs. Further trials are required to prove or refute this model.

A positron emission tomography study of the effects of treatment with valproate on brain 5-HT2A receptors in acute mania

OBJECTIVE

To examine the effects of treatment with valproate on brain 5-HT2A receptors in acute manic patients using positron emission tomography (PET) and [18F]-setoperone.

METHODS

Patients with DSM-IV bipolar I disorder-manic episode were recruited. Patients were drug free or drug naïve at the time of baseline PET scan. All patients were treated with valproate and one patient received lithium in addition to valproate for 3-5 weeks following which they had a post-treatment PET scan. The effect of treatment on brain 5-HT2A receptor binding was determined using statistical parametric mapping (SPM) and region of interest (ROI) analyses. Of the 12 manic patients recruited, seven patients had both baseline and post-treatment PET scans.

RESULTS

All seven patients improved with treatment and were in remission at the time of the second PET scan. Both SPM and ROI analyses showed that treatment with mood stabilizers had no significant effect on brain 5-HT2A receptor binding in manic patients.

CONCLUSION

This study suggests that changes in brain 5-HT2A receptors are not involved in the antimanic effects of mood stabilizers however, we cannot exclude the possibility of 5-HT2A receptor involvement in down-stream signaling pathways.

Structural and functional models of depression: from sub-types to substrates

OBJECTIVE

To present a functional model of depression facilitating research and clinical understanding.

METHOD

The authors conducted a systematic literature search and reviewed articles pertaining to the neurochemistry and pathophysiology of depressive disorders, focusing on the contribution made by the principal monoamines to three differing depressive structural sub-types (i.e. psychotic, melancholic and non-melancholic).

RESULTS

We suggest that the three structural depressive subtypes appear functionally underpinned by differential contributions of serotonergic, noradrenergic and dopaminergic neurotransmitters, so influencing phenotypic distinction (our structural model) and allowing an aetiological model to be derived with treatment specificity implications.

CONCLUSION

The functional model logically iterates with the structural model of depression and provides a useful framework for conceptualizing the depressive disorders. This model provides a logic for distinguishing between principal depressive subtypes, pursuing their functional underpinnings and explaining treatment differential effects across the three sub-types.

Neurochemical underpinnings in bipolar disorder and epilepsy

In this article, we discuss and highlight some of the potential neurochemical underpinnings of bipolar disorder (BD) and epilepsy. Some similarities are found in both disorders, such as the episodic course of the illnesses, the possible mechanism of kindling, and the efficacy of some antiepileptic drugs (AEDs) in treatment, all pointing to a common underlying pathophysiology. Common mechanisms at the level of ion channels might include the antikindling and the calcium-antagonistic and potassium outward current-modulating properties of AEDs. However, future research on intracellular mechanisms might become decisive for a better understanding of the similarities between the disorders.

Risperidone Does Not Affect Steady-State Pharmacokinetics of Divalproex Sodium in Patients with Bipolar Disorder

OBJECTIVE

Divalproex sodium can interact with many drugs in which combination treatments are used; it can increase plasma concentrations of some drugs by inhibiting metabolism and can increase the free fractions of other medications by displacing them from plasma proteins. The combination of risperidone and divalproex sodium is used to treat the manic phase of bipolar disorder. However, the effect of risperidone on the pharmacokinetics of valproate has not previously been systematically studied. The aims of this study were to determine the effect of repeated doses of oral risperidone on the pharmacokinetics of valproate in subjects stabilised on divalproex sodium and to document the safety of this combination.

STUDY DESIGN

A multicentre, observational, randomised, parallel group, single-blind, placebo-controlled drug interaction study.

PATIENTS

Twenty-two patients with bipolar disorder, in remission, were studied.

METHODS

All subjects were treated with divalproex sodium 1000 mg/day monotherapy on days 1-14. Thereafter, subjects continued to take divalproex sodium for days 15-28; they also received adjunctive treatment with either placebo (n = 11) or risperidone (n = 11) 2mg once daily on days 15 and 16, and 4 mg once daily on days 17-28. Serial blood sampling was performed throughout to determine the plasma concentrations of valproate, risperidone and 9-hydroxy-risperidone.

RESULTS

On analysis, steady-state pharmacokinetic parameters (peak plasma concentrations [C(max)], time to C(max,) area under the concentration-time curve) of valproate were of the same order of magnitude on day 14 (monotherapy) and day 28 (valproate plus risperidone or placebo), with no period effect. The parameters on day 28 were similar in the risperidone and placebo treatment groups, showing that risperidone, as adjunctive treatment, had no influence on the steady-state pharmacokinetics of valproate. Although there were more adverse events reported in the risperidone group compared with the placebo group (ten vs seven, respectively), none of them were serious or necessitated withdrawal. No clinically relevant changes in laboratory parameters, vital signs or ECG-tracings were observed in either group.

CONCLUSION

These results indicate that adjunctive risperidone treatment had no influence on the steady-state pharmacokinetics of valproate and this combination was safe and well tolerated.

Transtorno de estresse pós-traumático e transtorno de humor bipolar

O Transtorno Bipolar (THB) não é somente uma condição endógena. Severos eventos negativos durante a vida influenciam o desenvolvimento do primeiro episódio e alteram o curso do THB durante a vida. O Transtorno de Estresse Pós-Traumático (TEPT) é uma severa e incapacitante doença mental que afeta uma significativa parcela da população, em algum momento de suas vidas. A presença concomitante de TEPT e THB parece mais freqüente que anteriormente sugerido, e pacientes psicóticos com história de trauma tem sintomas mais severos e maior tendência a abusar de substância psicoativas ilícitas. Pensamentos intrusivos e pesadelos ocorrem com freqüência nos pacientes com TEPT e têm sido associados aos transtornos de humor. O tratamento farmacológico dessa comorbidade ainda está relacionado a estudo empíricos ou não-controlados. Neste artigo, são revisados aspectos atuais relacionados a essa comorbidade e enfatizados aspectos referentes à epidemiologia, etiologia, curso e tratamento farmacológico da comorbidade entre TEPT e THB. Especialmente, este estudo enfatiza a importância de avaliar sistematicamente a história de trauma em pacientes com THB.

Serotonergic dysregulation in bipolar disorders: a literature review of serotonergic challenge studies

OBJECTIVES

Serotonin (5-hydroxytryptamine; 5-HT) and endocrine abnormalities have been repeatedly reported in bipolar disorders (BD). Useful methods to investigate 5-HT responsivity, and the interaction with neuroendocrine functioning, are provided by acute 5-HT challenge and depletion paradigms. In this review 5-HT challenges are limited to paradigms that stimulate 5-HT activity in BD.

METHODS

Literature was searched for in electronic libraries: MEDLINE and PSYCHLIT, period 1966-2001. Papers describing effects of an acute 5-HT challenge on neuroendocrine functioning in BD patients were selected.

RESULTS

Review of the literature revealed 15 studies: five papers described the effects of 5-HT challenges in manic BD patients, four papers in euthymic BD and seven in depressed BD patients. The reviewed 5-HT challenge paradigms are acute administration of oral and intravenous (i.v.) dosage of d,l-fenfluramine, tryptophan, 5-hydroxytryptophan, ipsapirone and buspirone. There were no papers which investigated neuroendocrine effects of m-chlorophenylpiperazine, clomipramine and citalopram in BD patients and were therefore not reviewed.

CONCLUSIONS

The literature on 5-HT challenge procedures in BD shows evidence for a blunted prolactin (PRL) in mania and depression as well as a blunted cortisol in euthymic BD patients. This suggests that in both mania and depression similar changes in the 5-HT system are involved. It is speculated that blunting of cortisol responses in euthymic BD patients may be a result of chronically altered 5-HT functioning, whereas changes in PRL release following 5-HT challenges reflect more state-dependent changes in 5-HT activity. The 5-HT responsivity in BD patients has also been associated with pharmacological treatment, suicidal behaviour, weight loss and age. Recommendations for future research are given.

Psychomotor slowing, neuroendocrine responses, and behavioral changes after oral administration of meta-chlorophenylpiperazine in normal volunteers

The mixed 5-HT receptor agonist/antagonist meta-chlorophenylpiperazine (mCPP) is known to suppress locomotor activity in mice and rats. This study aimed: (1) to determine whether mCPP induces cognitive and motor changes in normal human volunteers and how these changes relate to the neuroendocrine effects of mCPP; and (2) to compare these cognitive and motor changes to the known cognitive and motor slowing patterns in depression and schizophrenia. A computerized method (used in previous research) analyzed fine motor behavior during figure-copying tasks. In 14 normal male volunteers behavioral responses, body temperature, plasma levels of prolactin and cortisol, and cognitive and motor performance during figure-copying tasks were measured after a single oral dose of mCPP (0.5 mg/kg). mCPP-induced prolongation of the reaction times in all copying tasks, parallel to increases in cortisol and prolactin and some self-reported behavioral effects. There were no changes in the movement times or the velocities of the writing movements. In conclusion, mCPP induced cognitive, but not motor slowing, in normal male volunteers. This indicates that the human serotonin system is also implicated in psychomotor behavior. This pattern of slowing was different from that in depressed and schizophrenic patients.

Serotonin and bipolar disorder

With the emergence of specific pharmacological probes for various serotonin (5-HT) receptors and radio-ligands for central 5-HT, it has now become possible to investigate its role in the pathogenesis of bipolar disorder more closely. This paper critically reviews the scientific literature regarding the relationship between bipolar disorder and serotonergic systems. The evidence suggests that central serotonergic activity is reduced in the depressive phase of bipolar disorder. Similar findings have been reported in bipolar patients when euthymic, indicating that that lower 5-HT activity could be a trait marker for bipolar disorder. Findings reported in the manic phase of this illness are inconsistent.

Serotonin in mania and in the mechanism of action of mood stabilizers: a review of clinical studies

OBJECTIVES

Serotonin (5-hydroxytryptamine, 5-HT) was implicated in the pathophysiology of manic-depressive illness as early as 1958. Although extensive evidence has accumulated since then to support 5-HT's role in depression, relatively fewer studies examined its role in mania. The purpose of this paper was to review and summarize the current state of knowledge on the role of 5-HT in mania and its treatment.

METHODS

We systemically reviewed clinical studies of 1) 5-HT function in mania and 2) 5-HT in the mechanism of action of mood stabilizers, including lithium and anticonvulsants.

RESULTS

Review showed that cerebrospinal fluid, postmortem, platelet, neuroendocrine challenge, and tryptophan depletion studies provided some evidence to support the hypothesis that a 5-HT deficit is involved in mania and that enhancement of 5-HT neurotransmission exerts a mood-stabilizing effect.

CONCLUSIONS

There is some evidence from clinical studies for the contribution of 5-HT in mania and in the mechanism of action of mood stabilizers. However, it is very likely that other neurotransmitters also play important roles. Future directions for research include 1) in vivo study of 5-HT receptor subtypes using positron emission tomography, 2) investigation of the interaction between 5-HT and other neurotransmitter systems, and 3) determination of the relationships between diagnostic subtypes of mania and 5-HT function and other neurotransmitter systems.

Plasma and urinary serotonin and 5-HIAA in children treated with lamotrigine for intractable epilepsy

Alteration of monoamine levels by some antiepileptic drugs (AEDs) was elucidated in this study. Lamotrigine (LTG) is a new AED, acting the sodium-channels. LTG was given as add-on therapy to 16 patients aged 4.5-18 yrs with intractable epilepsy and comedicated with carbamazepine or valproate. An equal group of epileptics with comparable clinical characteristics and treatment served as control. Plasma and urinary (24 h-samples) serotonin and 5-HIAA were determined before onset of LTG therapy and after 2-3 months. HPLC and electrochemical detection was used for the determination of serotonin (5-HT) and 5-hydroxy indoleacetic acid (5-HIAA). No significant effect of LTG on both urinary 5-HT and 5-HIAA levels was found, whereas plasma 5-HT concentrations significantly decreased in comparison with levels before LTG starting and relevant values in controls. This findings was noted in 7/16 children with favourable response to LTG. Increased serotonin catabolism may be result of LTG action.

Sodium valproate increases pupillary responsiveness to a cholinergic agonist in responders with mania

BACKGROUND

The cholinergic hypothesis of affective disorders predicts that mania is a hypocholinergic state relative to monoaminergic activity. Treatments that increase cholinergic sensitivity are expected to improve manic symptoms. Valproic acid is an effective treatment for mania. Little, however, is known about the cholinergic effects of this agent.

METHODS

Ten male hypomanic or manic patients were treated with valproic acid (1500-2000 mg) for 2 weeks. Cholinergic sensitivity was assessed before, and after treatment using graded concentrations of pilocarpine eyedrops (0.03-2.0%). Pupil size changes were quantified using an infrared pupillometer and ED50 values were referenced to maximal dilation with 0.5% tropicamide.

RESULTS

Valproate treatment decreased Bech mania ratings and ED50 values (p < .0001). Improvements in mania after treatment were closely correlated with decreases in ED50 (r = .76; p < .01). This relationship was indistinguishable from one previously observed after lithium treatment.

CONCLUSIONS

These results provide support for the cholinergic-adrenergic hypothesis. Moreover, similar pupillary reactions to valproic acid and lithium treatments suggest that these agents may share a common action on muscarinic receptors.

Valproate: a reappraisal of its pharmacodynamic properties and mechanisms of action

Valproate is currently one of the major antiepileptic drugs with efficacy for the treatment of both generalized and partial seizures in adults and children. Furthermore, the drug is increasingly used for therapy of bipolar and schizoaffective disorders, neuropathic pain and for prophylactic treatment of migraine. These various therapeutic effects are reflected in preclinical models, including a variety of animal models of seizures or epilepsy. The incidence of toxicity associated with the clinical use of valproate is low, but two rare toxic effects, idiosyncratic fatal hepatotoxicity and teratogenicity, necessitate precautions in risk patient populations. Studies from animal models on structure-relationships indicate that the mechanisms leading to hepatotoxicity and teratogenicity are distinct and also differ from the mechanisms of anticonvulsant action of valproate. Because of its wide spectrum of anticonvulsant activity against different seizure types, it has repeatedly been suggested that valproate acts through a combination of several mechanisms. As shown in this review, there is substantial evidence that valproate increases GABA synthesis and release and thereby potentiates GABAergic functions in some specific brain regions, such as substantia nigra, thought to be involved in the control of seizure generation and propagation. Furthermore, valproate seems to reduce the release of the epileptogenic amino acid gamma-hydroxybutyric acid and to attenuate neuronal excitation induced by NMDA-type glutamate receptors. In addition to effects on amino acidergic neurotransmission, valproate exerts direct effects on excitable membranes, although the importance of this action is equivocal. Microdialysis data suggest that valproate alters dopaminergic and serotonergic functions. Valproate is metabolized to several pharmacologically active metabolites, but because of the low plasma and brain concentrations of these compounds it is not likely that they contribute significantly to the anticonvulsant and toxic effects of treatment with the parent drug. By the experimental observations summarized in this review, most clinical effects of valproate can be explained, although much remains to be learned at a number of different levels of valproate's mechanisms of action.

Sensitization and kindling phenomena in mood, anxiety, and obsessive-compulsive disorders: the role of serotonergic mechanisms in illness progression

A number of untreated or inadequately treated psychiatric illnesses often demonstrate syndrome progression manifested by either increasing frequency, severity, or spontaneity of episodes. Behavioral sensitization to psychomotor stimulants (and its cross sensitization to stress) and electrophysiological kindling provide two very different models for conceptualizing physiological and behavioral abnormalities that progress in severity in response to the same inducing stimulation over time. These models are highly indirect, and the behaviors induced and specific pharmacologic interventions do not directly parallel those in many of these psychiatric syndromes. Nonetheless, these preclinical models help us conceptualize potential mechanisms involved in syndrome progression based on experience-dependent modifications of the genome at the level of transcriptional regulation. In both preclinical models, agents that are effective in the earlier developmental phase of sensitization or kindling are not necessarily effective in amelioration of the full-blown syndromes, and vice versa. Thus these models also suggest a variety of intervention principles that can be directly tested in the clinic, such as differential efficacy of treatment as a function of stage of evolution of the given syndrome. Although serotonergic mechanisms do not appear central to the basic phenomena of sensitization and kindling, they appear capable of modulating their development and severity. As such, it becomes of considerable importance to assess whether serotonergic mechanisms that have been implicated in acute treatment of mood and anxiety syndromes are also involved in the longitudinal course and prevention of syndrome progression or occurrence. Identification of the more precise molecular mechanisms involved might provide a target for new therapeutic approaches to these recurrent and potentially disabling major psychiatric illnesses.