[Treatment strategy of refractory depression and its presynaptic mechanism of action]

Most antidepressants used in Japan are reuptake inhibitors of monoamine, such as noradrenaline and serotonin. Incidence of refractory depression, which is resistant to at least two monoamine reuptake inhibitors, is 10-20%. ECT and the addition of lithium, thyroid hormones or dopamine agonists is used for the treatment of refractory depression. Bupropion and MAO inhibitors are also effective for refractory depression but not approved in Japan. The presynaptic mechanism of action of these antidepressants has been studied by in vivo microdialysis studies. Serotonin reuptake inhibitors increase extracellular serotonin concentrations in the brain. Noradrenaline reuptake inhibitors increase extracellular noradrenaline concentrations in the brain, and increase extracellular dopamine concentrations in the frontal cortex, but not in the nucleus accumbens or striatum. ECT and MAO inhibitors increase extracellular serotonin concentrations in the brain, and ECT, bupropion and MAO inhibitors increase extracellular noradrenaline concentrations in the brain. In contrast to monoamine reuptake inhibitors, ECT, bupropion and MAO inhibitors increase extracellular dopamine concentrations not only in the frontal cortex but also in the nucleus accumbens and striatum. The facilitation of mesolimbic or nigrostriatal dopamine neurotransmission may be the mechanism of action behind these treatments' efficacies for refractory depression. Although there are only a few studies concerning the mechanism of action of augmentation therapy, recent studies demonstrated that subchronic lithium treatment increases basal concentrations of extracellular serotonin in the frontal cortex and hippocampus. Subchronic lithium further increases SSRI-induced increases in extracellular serotonin concentrations, and this effect is suggested to be the mechanism of action for lithium augmentation of antidepressants.

Changes in human in vivo serotonin and dopamine transporter availabilities during chronic antidepressant administration

Few studies have demonstrated in vivo alterations of human serotonin and dopamine transporters (SERTS and DATS) during antidepressant treatment. The current study measured these transporter availabilities with [(123)I]beta-CIT single photon emission computed tomography (SPECT) during administration of selective serotonin reuptake inhibitors (SSRIs) or a non-SSRI, bupropion. A total of 17 healthy human subjects were randomly assigned to two different treatment protocols: (1). citalopram (40 mg/day) followed by augmentation with bupropion (100 mg/day) or (2). bupropion (100-200 mg/day) for 16 days. Citalopram significantly inhibited [(123)I]beta-CIT binding to SERT in brainstem (51.4%) and diencephalon (39.4%) after 8 days of administration, which was similarly observed after 16 days. In contrast, citalopram significantly increased striatal DAT binding by 15-17% after 8 and 16 days of administration. Bupropion and its augmentation to citalopram did not have a significant effect on DAT or SERT. In 10 depressed patients who were treated with paroxetine (20 mg/day), a similar increase in DAT and inhibition of SERT were observed during 6 weeks treatment. The results demonstrated the inhibition of SERT by SSRI in human in vivo during the chronic treatment and, unexpectedly, an elevation of DAT. This apparent SSRI-induced modulation of the dopamine system may be associated with the side effects of these agents, including sexual dysfunction.

[11C]-DASB, a tool for in vivo measurement of SSRI-induced occupancy of the serotonin transporter: PET characterization and evaluation in cats

The in vivo pharmacological profile of [(11)C]-DASB, a new radioligand developed for in vivo imaging of the serotonin transporter (SERT), was evaluated in the cat brain using positron emission tomography (PET). The in vivo distribution of [(11)C]-DASB binding was consistent with the known distribution of SERT sites in the cat brain in vitro with high uptakes of radioactivity in the midbrain and thalamus, intermediate levels in striatum, and modest to low levels of radioactivity in the neocortex and cerebellum, respectively. [(11)C]-DASB binding potential (BP) values ranged from about 0.2 in the neocortex to 2.2 in the midbrain. Radioligand binding in all brain regions except cerebellum was markedly reduced following pretreatment with fluoxetine and citalopram, but was unaffected by pretreatment with GBR12909, maprotiline, and haloperidol, indicating specificity of [(11)C]-DASB binding to the SERT. Two cats were each examined using PET and [(11)C]-DASB in a longitudinal fashion (from 30 min and up to 24 days) following a single i.v. dose of: 1) fluoxetine, and 2) citalopram at different dosages. Both drugs induced similar degrees of SERT occupancy at 30 min postinjection (approximately 90%). A comparison of citalopram and fluoxetine pharmacokinetics in the same animal and at the same dosage (1 mg/kg) showed that citalopram SERT occupancy and plasma half-lives were 9 times and 14 times shorter, respectively, than those of fluoxetine and norfluoxetine. In addition, studies performed after injection of the monoamine oxidase inhibitor tranylcypromine suggested that high levels of synaptic serotonin may compete with [(11)C]-DASB for binding on the SERT. These studies indicate that [(11)C]-DASB is a suitable PET radioligand for measuring drug occupancy of the SERT in vivo and has potential for monitoring in vivo changes in serotonin levels.

Effects of acute treatment with 8-OH-DPAT and fluoxetine on aggressive behaviour in male song sparrows (Melospiza melodia morphna)

The role of serotonin in modulating male aggressive behaviour was investigated in male song sparrows, Melospiza melodia morphna, using two different serotonergic drugs, fluoxetine and 8-OH-DPAT. Fluoxetine is a selective serotonin reuptake inhibitor of the neuronal reuptake pump increasing synaptic concentrations of serotonin, and 8-OH-DPAT is a specific serotonin (5-HT1A) receptor agonist. The serotonergic control of aggression in passerines has not been previously investigated. We examined these behaviours within a controlled setting using a laboratory simulated territorial intrusion, with a hierarchical scale to quantify male-male aggressive behaviour. Utilizing this scale, we quantified the extent of male aggressive behaviour in two experiments. In experiment 1, song sparrows were given 100 micro l, s.c. injections of either fluoxetine (10 mg/kg) or 8-OH-DPAT (1 mg/kg). Experiment 2 was a dose-response study using three doses of 8-OH-DPAT (0.1, 1 and 10 mg/kg). In both studies, aggressive behaviour was measured 1 h after injection for 10 min in response to the presence of a novel male decoy combined with playback of conspecific song. Both drugs significantly reduced male aggressive behaviour, and 8-OH-DPAT did so in a dose-dependent manner. The effect of the two drugs upon general activity was also measured using infra-red perch hop detectors. Activity levels were not effected by either fluoxetine or 8-OH-DPAT at all of the respective doses, indicating that the reduction in aggressive behaviour was specific. These results demonstrate that, in a passerine species, the serotonergic system negatively regulates male-male aggressive behaviour. These results further demonstrate that aggression can be effectively studied in a laboratory setting and natural aggressive responses can be elicited using this method.

Rat strain differences in peripheral and central serotonin transporter protein expression and function

Female Fischer 344 (F344) rats have been shown to display increased serotonin transporter (5-HTT) gene expression in the dorsal raphe, compared to female Lewis (LEW) rats. Herein, we explored, by means of synaptosomal preparations and in vivo microdialysis, whether central, but also peripheral, 5-HTT protein expression/function differ between strains. Midbrain and hippocampal [3H]paroxetine binding at the 5-HTT and hippocampal [3H]serotonin (5-HT) reuptake were increased in male and female F344 rats, compared to their LEW counterparts, these strain differences being observed both in rats of commercial origin and in homebred rats. Moreover, in homebred rats, it was found that these strain differences extended to blood platelet 5-HTT protein expression and function. Saturation studies of midbrain and hippocampal [3H]paroxetine binding at the 5-HTT, and hippocampal and blood platelet [3H]5-HT reuptake, also revealed significant strain differences in Bmax and Vmax values. Although F344 and LEW rats differ in the activity of the hypothalamo-pituitary-adrenal (HPA) axis, manipulations of that axis revealed that the strain differences in hippocampal [3H]paroxetine binding at 5-HTTs and [3H]5-HT reuptake were not accounted for by corticosteroids. Hippocampal extracellular 5-HT levels were reduced in F344 rats, compared to LEW rats, with the relative, but not the absolute, increase in extracellular 5-HT elicited by the local administration of citalopram being larger in F344 rats. Because the aforementioned strain differences did not lie in the coding sequences of the 5-HTT gene, our results open the promising hypothesis that F344 and LEW strains model functional polymorphisms in the promoter region of the human 5-HTT gene.

5-HT2A receptor activation leads to increased BDNF mRNA expression in C6 glioma cells

It has recently been suggested that an increase in brain-derived neurotrophic factor (BDNF) expression may mediate some of the therapeutic effect of antidepressant drugs, via their effects on the neurotransmitter 5-hydroxytryptamine (5-HT). However, because it is unclear whether 5-HT manipulations directly affect BDNF expression, we examined BDNF mRNA levels in C6 glioma cells following incubation with 5-HT using reverse transcription polymerase chain reaction (RT-PCR) and Northern blot analysis. Incubation of C6 glioma cells with 5-HT increased the BDNF mRNA expression approx twofold. The effect of 5-HT (100 microM) was inhibited by a 5-HT2A receptor antagonist (ketanserin; 1 microM). The RNA synthesis inhibitor (actinomycin D; 10 microg/mL), but not a protein synthesis inhibitor (cycloheximide; 0.5 microg/mL) blocked the effect of 5-HT. Furthermore, incubation of C6 glioma cells with EGTA (1 mM), a protein kinase inhibitor (staurosporine; 1 microM), the Ca2+ ATPase inhibitor thapsigargin (1 microM), or a calcium/calmodulin-dependent kinase inhibitor (KN 62; 1 microM) inhibited the response to 5-HT. Our data show that 5-HT increases de novo BDNF mRNA synthesis following direct activation of the 5-HT2A receptor, via a calcium-dependent and protein kinase-dependent pathway.

Interaction of sertraline with Candida species selectively attenuates fungal virulence in vitro

This study investigated whether the interaction between isolates of Candida albicans (n=7), Candida parapsilosis (n=3), Candida krusei (n=2), Candida dubliniensis (n=1) and sertraline, a typical selective serotonin reuptake inhibitor, alters candidal virulence. Sertraline treatment of Candida spp. significantly (P<0.05) affected hyphal elongation, phospholipase activity, production of secreted aspartyl proteinases and fungal viability. In addition, monocyte-derived macrophages (MDMs) treated with sertraline reduced inhibition of blastoconidia germination in comparison to MDMs alone. In conclusion, our findings suggest that the interaction between sertraline and Candida spp. may also diminish the virulence properties of this fungal pathogen in vivo.

5-Hydroxytryptamine and platelets: uptake and aggregation in hypoxic pulmonary hypertensive rats

Pulmonary hypertension is associated with various alterations in 5-hydroxytryptamine (5-HT) physiology. In this study in platelets from hypoxic pulmonary hypertensive rats (10% O(2); 1 week) and normoxic rats (room air), (i) initial rates of specific [3H]5-HT uptake were measured and (ii) potentiation of collagen- and ADP-induced aggregation by 5-HT was quantified. The platelet count was almost halved in hypoxic rats. In uptake experiments, there was a decrease in 5-HT uptake in platelets from hypoxic compared with normoxic rats, due to a 36% reduction in the maximal initial rate of uptake. The aggregation experiments showed that 5-HT (1-100 microM) increased the magnitude of responses to collagen and the duration of responses to ADP, but there was no difference between hypoxic and normoxic rats. Abnormalities in platelet function may conceivably lead to increases in plasma 5-HT levels in hypoxic pulmonary hypertension, but are unlikely to aggravate pulmonary thromboembolism.

Local, but not systemic, administration of serotonergic antidepressants decreases hippocampal nitric oxide synthase activity

Nitric oxide (NO) is an unconventional transmitter molecule in the nervous system, synthesized by nitric oxide synthase (NOS) following activation of the N-methyl-D-aspartate (NMDA) receptor. Several in vivo studies have demonstrated that NO modulates the extracellular levels of various neurotransmitters in the central nervous system, while serotonin (5-HT) re-uptake may be influenced by the NO pathway. Moreover, inhibitors of NOS exhibit antidepressant-like and anxiolytic-like properties in various animal models. Therefore, the aims of the present study were to clarify the involvement of distinct antidepressants acting on the serotonin re-uptake site in the regulation of the activity of hippocampal NOS in vitro, in vivo and ex vivo. We found that citalopram, paroxetine, imipramine and N(G)-nitro-L-arginine dose dependently decreased the hippocampal NOS activity in vitro. Moreover, local administration of citalopram, paroxetine, tianeptine, imipramine and N(G)-nitro-L-arginine significantly decreased the hippocampal NOS activity in vivo at a concentration significantly lower than in vitro. No effect on NOS activity following retrodialysis with 5-HT was observed. Acute (5 mg/kg, s.c.) and chronic (3 weeks, 20 mg/kg/24 h) systemic administration of citalopram did not influence NOS activity ex vivo. The effects on NOS represent a response to structurally dissimilar serotonergic antidepressants. However, since these data reflect effects on basal NOS activity, we believe that serotonergic antidepressants do not directly affect NOS at dosages used clinically, but the findings may reflect a secondary action of antidepressants on the glutamate NMDA receptor following their primary inhibitory action at the 5-HT transporter.

Fluvoxamine suppresses the long-term potentiation in the hippocampal CA1 field of anesthetized rats: an effect mediated via 5-HT1A receptors

A selective 5-HT reuptake inhibitor, fluvoxamine (10 and 30 mg/kg, i.p.) suppressed long-term potentiation (LTP) in the hippocampal CA1 field of anesthetized rats. Fluvoxamine (30 mg/kg, i.p.)-induced suppression of LTP was completely reversed by the 5-HT(1A) receptor antagonist NAN-190 (0.5 mg/kg, i.p), but not by the 5-HT(4) receptor antagonist GR 113808 (20 microg/rat, i.c.v.) and the 5-HT(7) receptor antagonist DR 4004 (10 microg/rat, i.c.v.). These data suggest that the inhibitory effect of fluvoxamine on LTP induction is mediated via 5-HT(1A) receptors.

Effect of fenfluramine on caloric intake and macronutrient selection in Lou/c rats during aging

Previous studies have shown a shift of preferences from carbohydrate to fat and a decrease in protein intake in self-selected Lou/c rats with advancing age. This study investigated a potential neurochemical mechanism underlying age-related modifications by evaluating the effects of fenfluramine (dl-F), a drug that enhances 5-HT release and blocks its re-uptake by presynaptic terminals, on macronutrient selection. The drug dl-F (1.5 and 3mg/kg s.c.) induces a dose-related hypophagia with the oldest animals being the most sensitive. The main decrease is in fat consumption with minor changes in carbohydrate and protein consumptions. Young, but not old animals, compensate during the day the nocturnal intake decrease induced by dl-F. The plasma concentration of dexfenfluramine (d-F) was higher as the rats aged. The icv administrations of dl-F induced a caloric intake decrease in the oldest groups and a differential effect on protein intake between old and young rats. Metergoline induced a partial reversion of dl-F effect on food intake but this effect was not age related. These data suggest a possible implication of serotoninergic system in modifications of food behavior during aging. However, further studies are needed.

Reboxetine versus paroxetine versus placebo: effects on cognitive functioning in depressed patients

Impaired cognitive functioning is often associated with major depressive disorder (MDD). Moreover, a number of agents used to treat MDD are known to have negative effects on cognitive functioning. We report an assessment of the effects of the selective norepinephrine reuptake inhibitor reboxetine, the selective serotonin reuptake inhibitor paroxetine, and placebo on a variety of measures of cognitive functioning in patients with MDD. Cognitive functioning in 74 adult patients (aged 18-65 years) with a confirmed diagnosis of MDD (DSM-IV) was assessed as part of two identical, randomized, double-blind, placebo- and active-treatment-controlled, fixed/flexible dose comparisons of 8 weeks of treatment with reboxetine (8-10 mg/day), paroxetine (20-40 mg/day) and placebo. Cognitive function was assessed at baseline, day 14 and day 56 using a selection of tasks from the Cognitive Drug Research computerized assessment system, including Simple Reaction Time, Digit Vigilance, Choice Reaction Time, Numeric Working Memory, Word Recognition and Critical Flicker Frequency. The results in the 74 patients (reboxetine n = 25, paroxetine n = 23, placebo n = 26) showed that reboxetine significantly improved the ability to sustain attention at day 56 compared with baseline (P = 0.023). In addition, patients who received reboxetine experienced significant improvements in their speed of cognitive functioning when tested at day 56 compared to baseline (P = 0.024). No significant changes or trends in this direction were seen among patients who received either placebo or paroxetine. The results of the present study provide objective data to support the possibility that reboxetine favourably affects cognitive processes in depressed patients.

Role of 5-HT receptors in treatment of overactive bladder

Normal bladder function requires coordinated detrusor relaxation and urethral sphincter contraction during the filling phase and the reverse during micturition. This is achieved by the integration of excitatory, inhibitory, and sensory nerve activity in control centers in the spinal cord, pons, and forebrain. It is possible that much of bladder pathology is related to disturbances in the vesical ganglia, sensory reflex loops, and central control of micturition. Experimental studies in animals have revealed that spinal reflex circuits involved in voiding function exhibit a dense serotonergic innervation, multiple 5-HT receptors, and sensitivity to 5-HT receptor agonists and antagonists, and 5-HT reuptake inhibitors. Activity in the serotonergic pathway generally enhances urine storage by facilitating the vesical sympathetic reflex pathway and inhibiting the parasympathetic voiding pathway. Thus, 5-HT receptor antagonists and reuptake inhibitors represent important targets for the development of new treatments of detrusor overactivity and urinary incontinence. Among the drugs modulating the bladder function through 5HT receptor, duloxetine, a potent and selective inhibitor of 5-HT and NE reuptake, is presently undergoing clinical trials for stress urinary incontinence after being shown to be effective in animal models of this condition.

Evidence that acute serotonergic activation potentiates the locomotor-stimulating effects of corticotropin-releasing hormone in juvenile chinook salmon (Oncorhynchus tshawytscha)

The present study investigated whether the serotonergic system is involved in mediating the behavioral effects of corticotropin-releasing hormone (CRH) in juvenile spring chinook salmon, Oncorhynchus tshawytscha. An intracerebroventricular (ICV) injection of CRH induced hyperactivity. The effect of CRH was potentiated in a dose-dependent manner by the concurrent administration of the serotonin (5-HT) selective reuptake inhibitor fluoxetine. However, administration of fluoxetine alone had no effect on locomotor activity, suggesting that the locomotor-stimulating effect of CRH is mediated by the activation of the serotonergic system. Conversely, ICV injections of the 5-HT(1A) receptor antagonist NAN-190 attenuated the effect of CRH on locomotor activity when given in combination with CRH but had no effect when administered alone. These results provide the first evidence to support the hypothesis that the effect of CRH on locomotor activity in teleosts is mediated by activating the serotonergic system.

Treatment of depression with comorbid anxiety disorders: differential efficacy of paroxetine versus moclobemide

To compare the efficacy and tolerability of moclobemide versus paroxetine for the treatment of depression with comorbid anxiety disorders. Outpatients fulfilling DSM-III-R criteria for major depression or dysthymia and for a co-occurring comorbid anxiety disorder (panic disorder, generalized anxiety disorder or obsessive-compulsive disorder) after a 1-week run-in phase were randomly assigned to open-label moclobemide (300-600 mg/day) or paroxetine (20-40 mg/day) for 4 months. Primary criterion for response was a 50% score reduction from baseline on Hamilton Depression Rating Scale and Hamilton Anxiety Rating Scale scores. Mean changes in Clinical Global Impressions Severity of Illness and Improvement Scales (CGI-I) were also used to evaluate treatment response. Of the 123 patients included in the study, 65 were randomly assigned to moclobemide and 58 to paroxetine. At study end, the two treatment groups did not differ significantly in terms of proportion of responders. Treatment group differences emerged when comorbid anxiety diagnoses were considered. In patients with comorbid panic disorder, paroxetine was superior to moclobemide in improving both anxiety and depression (five patients out of 18 in the moclobemide group and nine out of 14 in the paroxetine group were rated as responders according to CGI-I, P = 0.04). Neither medication was superior in treating comorbid generalized anxiety disorder. These findings indicate that both moclobemide and paroxetine are effective for treatment of depression with comorbid anxiety disorders. However, in the subgroup with comorbid panic disorder, paroxetine is more effective than moclobemide in reducing both depressive and anxiety symptoms.

Chronic fluoxetine induces opposite changes in G protein coupling at pre and postsynaptic 5-HT1A receptors in rat brain

Chronic treatment with the antidepressant fluoxetine may lead to changes in the properties of pre- and postsynaptic 5-HT(1A) receptors due to modifications in the receptor-G protein coupling process. We have evaluated, in rats, the effect of chronic fluoxetine (10 mg/kg/day) at brain 5-HT(1A) receptors using different techniques. The density of 5-HT(1A) receptors was unchanged in fluoxetine-treated rats vs. vehicle group. Stimulation of [(35)S]GTPgammaS binding induced by (+/-)8-OH-DPAT was significantly attenuated in dorsal raphe nucleus after fluoxetine (+3.7 vs. +31.2% in vehicle). The inhibition of dorsal raphe firing by (+/-)8-OH-DPAT (ED(50) in vehicle = 2.1 microg/kg, i.v.) was also attenuated in rats treated with fluoxetine (ED(50)=4.7 microg/kg). In contrast, a significant increase on (+/-)8-OH-DPAT-induced stimulation of [(35)S]GTPgammaS binding was observed in CA(1) (+53.4 vs.+20.2% in vehicle) and dentate gyrus (+105.7 vs. +52.6% in vehicle) but not in entorhinal cortex. Our data demonstrate that fluoxetine-induced desensitization of 5-HT(1A) autoreceptors occurs at G protein level. Moreover, a relevant finding is the region-specific hypersensitivity of postsynaptic 5-HT(1A) receptors, in the hippocampus but not in entorhinal cortex, following chronic fluoxetine. These differential adaptive changes in brain 5-HT(1A) receptors could underlie the mechanism of action of antidepressants and also contribute to their clinical effects.

Antipsychotic augmentation for treatment resistant obsessive-compulsive disorder: what if antipsychotic is discontinued?

The aim of the present study was to retrospectively review the charts of obsessive-compulsive disorder (OCD) patients who responded to the addition of an antipsychotic to the seroronin reuptake inhibitor (SRI), and who subsequently discontinued the antipsychotic, in order to evaluate whether antipsychotic discontinuation resulted in a relapse of the disorder. Charts of patients with a principal diagnosis of OCD (DSM-IV) treated with pharmacotherapy were reviewed in order to select patients who: (i) did not respond to a trial with a first-line drug (clomipramine or a selective SRI); (ii) received an antipsychotic at low doses (haloperidol, pimozide, risperidone or olanzapine) in order to potentiate the SRI; (iii) responded to this augmentation strategy; and (iv) discontinued the antipsychotic drug for any reason while continuing the SRI at the same dose. Relapse was defined as a worsening of Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) total score >/= 35% with respect to last evaluation before antipsychotic discontinuation or, for patients with a Y-BOCS < 16 at the end of the combination period, as a Y-BOCS total score >/= 16 at any time after antipsychotic discontinuation. According to our definition of relapse, 15 patients out of 18 (83.3%) relapsed after antipsychotic discontinuation, with a mean worsening of symptoms of 6.6 +/- 1.7 points in the Y-BOCS total score. Thirteen patients out of the 15 who relapsed did so by week 8 after discontinuation. Two subjects relapsed at the end of the 1-year study. Although retrospective, our study provides initial evidence that antipsychotic augmentation has to be maintained for patients who respond to this strategy, because the vast majority of subjects who discontinue the antipsychotic relapse within 2 months.

Positron emission tomography of regional brain metabolic responses to a serotonergic challenge and lethality of suicide attempts in major depression

BACKGROUND

Lower serotonergic activity correlates with high-lethality suicide attempts in major depression. Postmortem studies of serotonin receptors in suicides localize changes to the ventral prefrontal cortex (PFC). We studied serotonergic response in ventral PFC in depressed patients surviving a high-lethality suicide attempt.

METHODS

Depressed patients with a history of a high-lethality suicide attempt (n = 16) were compared with those with low-lethality attempts (n = 9) for level of depression, suicidal intent and ideation, impulsivity, aggression, and neuropsychological test performance. Subjects were scanned while medication free after a single-blind placebo and after fenfluramine hydrochloride administration on a second day. Brain responses were measured by positron emission tomography imaging of fludeoxyglucose F 18 and serial prolactin levels. Scans were compared by means of statistical parametric mapping. Correlations of changes in relative regional cerebral uptake (rCMRglu) with clinical and neuropsychological measures were assessed.

RESULTS

Depressed high-lethality suicide attempters had lower rCMRglu in ventral, medial, and lateral PFC compared with low-lethality attempters. This difference was more pronounced after fenfluramine administration. Lower ventromedial PFC activity was associated with lower lifetime impulsivity, higher suicidal intent (planning), and higher-lethality suicide attempts. Higher verbal fluency was positively correlated with rCMRglu in the same regions.

CONCLUSIONS

Prefrontal localized hypofunction and impaired serotonergic responsivity are proportional to the lethality of the suicide attempt and may mediate the effects of suicide intent and impulsivity on lethality. Positron emission tomographic neuroreceptor studies are needed to determine whether postmortem serotonin receptor findings are also present in vivo and contribute to the abnormal rCMRglu responses.

Dose-related effects of chronic antidepressants on neuroprotective proteins BDNF, Bcl-2 and Cu/Zn-SOD in rat hippocampus

It has been proposed that antidepressants have neuroprotective effects on hippocampal neurons. To further test this hypothesis, brain-derived neurotrophic factor (BDNF), B cell lymphoma protein-2 (Bcl-2), and copper-zinc superoxide dismutase (Cu/Zn-SOD) were examined immunohistochemically in hippocampal neurons of Sprague-Dawley rats following daily treatment with 5 or 10 mg/kg of amitriptyline or venlafaxine for 21 days. At 5 mg/kg, both amitriptyline and venlafaxine increased the intensity of BDNF immunostaining in hippocampal pyramidal neurons, and the intensity of Bcl-2 immunostaining in hippocampal mossy fibers, but did not alter the Cu/Zn-SOD immunoreactivity. The high dose of venlafaxine, however, decreased the intensity of BDNF immunostaining in all subareas of the hippocampus and increased the intensity of Cu/Zn-SOD immunostaining in the dentate granular cell layer. The high dose of amitriptyline increased the intensity of Cu/Zn-SOD immunostaining, but did not affect the immunoreactivity of Bcl-2 or BDNF. These findings suggest that the chronic administration of amitriptyline or venlafaxine at 5 mg/kg, but not 10 mg/kg, may be neuroprotective to hippocampal neurons. These dose-related effects of antidepressant drugs on hippocampal neurons may have relevance to disparate findings in the field.

Effect of a pharmacological intervention on quality of life in patients with obsessive-compulsive disorder

Patients with obsessive-compulsive disorder (OCD) not only suffer from obsessive-compulsive symptoms, but also the disorder is associated with aberrant social functioning and a diminished quality of life (QoL). Although studies concerning the effect of treatment interventions on symptoms are common, studies with regard to the effect of treatment interventions on QoL are scarce. We examined the effect of a pharmacological intervention on QoL in 150 patients with OCD. Furthermore, we studied whether two different drugs, venlafaxine and paroxetine, differed in their effect on QoL. Finally, we examined whether any found improvement in QoL was related to improvement in symptoms and/or the baseline self-directedness score, which is one of the character dimensions of the psychobiological model of Cloninger. We demonstrated that QoL, as assessed with the Lancashire Quality of Life Profile, improved following pharmacological intervention, for which paroxetine and venlafaxine appeared to be equally effective. Furthermore, neither improvement in symptoms, nor baseline self-directedness, was associated with the improvement in QoL.

Overview of the safety of citalopram

Citalopram is a highly selective serotonin reuptake inhibitor (SSRI) that has been prescribed to >30 million patients in >70 countries. The purpose of this focused overview is to summarize the data from well-controlled clinical trials and published literature relative to the safety of citalopram in patients with depression and depressive symptoms. This overview is based mainly on 3 sources: (1) data from clinical trials sponsored by Forest Laboratories, (2) published clinical studies, and (3) case reports. Both pharmacokinetic and pharmacodynamic interactions were scrutinized, as were data on special populations and safety concerns. The available data suggest that citalopram 20-60 mg once daily is safe for patients with depression. Few drugs appear to interact with citalopram in a clinically meaningful way. Well-designed short- and long-term trials demonstrate an overall safety/side effect profile consistent with other SSRIs. The more frequent adverse events (nausea, somnolence, dry mouth, increased sweating) are mainly transient, mostly mild to moderate in severity, and observed consistently across studies at rates similar to other SSRIs. Analysis of laboratory values, ECG, and vital signs revealed no unusual findings. Only a small, clinically unimportant reduction in heart rate was observed, similar to that seen with other SSRIs. Citalopram treatment did not increase risk of suicide, overdose, seizure, or arrhythmia. Thus, the pharmacodynamic, pharmacokinetic, and safety profiles of citalopram demonstrate that it is safe for use in adults with depression and depressive symptoms, including the elderly and patients with mild to moderate renal and hepatic disease.

S-[18F]fluoromethyl-(+)-McN5652, a PET tracer for the serotonin transporter: evaluation in rats

The [(18)F]fluoromethyl analog of (+)-McN5652 ([(18)F]FMe-McN) for imaging serotonin transporter (SERT) with positron emission tomography (PET) has recently been synthesized. We describe here the biological evaluation of [(18)F]FMe-McN in rats. Biodistribution studies of [(18)F]FMe-McN in rat brain ex vivo after an intravenous injection showed a high accumulation of radioactivity in the regions rich in SERT, such as raphe nuclei, hypothalamus, thalamus, substantia nigra, locus coeruleus, and amygdala. Region-to-cerebellum ratios reached a maximum value of 9 in raphe nuclei within 3.5 h after administration. The specificity and selectivity of [(18)F]FMe-McN binding to SERT was studied by preinjecting blocking doses of serotonin, norepinephrine, and dopamine transporter inhibitors. Fluoxetine, a specific inhibitor for SERT, decreased the specific binding of [(18)F]FMe-McN in raphe nuclei by 91 +/- 4%; in other regions rich in SERT, similar results were obtained. GBR12909 and nisoxetine, selective inhibitors for dopamine transporter (DAT) and norepinephrine transporter (NET), respectively, showed no significant effects on the uptake of [(18)F]FMe-McN. Our studies show that [(18)F]FMe-McN has a clear potential as a tracer for studies with PET of SERT function in humans.

Anxiety induced by repetitive transcranial magnetic stimulation is suppressed by chronic treatment of paroxetine in rats

Repetitive transcranial magnetic stimulation (rTMS) has been shown to have a therapeutic effect on affective disorder and anxiety disorders. However, some reports have linked rTMS to a significant increase in anxiety in normal volunteers. This study investigates the effect of rTMS on anxiety and the use of acute and chronic paroxetine treatment on this animal model of anxiety. In normal rats, rTMS for 10 days induced anxiety, as shown by elevated plus maze, black and white box, and conditioned fear tests. This anxiety was suppressed by chronic, but not acute, paroxetine. These results suggest that rats receiving chronic rTMS treatment can be used as a model of anxiety and that the anxiety induced by rTMS might involve the serotonergic system.

Soy and social stress affect serotonin neurotransmission in primates

Stress and sex steroidal milieu can each influence mood in women. The purpose of this study was to compare the effect of long-term conjugated equine estrogen (CEE), soy phytoestrogen (SPE), and social subordination stress on dorsal raphe serotonin neurotransmission of ovariectomized cynomolgus monkeys. Tryptophan hydroxylase (TPH) and serotonin reuptake transporter (SERT) protein content were determined, and the in vitro degradation of macaque SERT protein was examined in the presence and absence of protease inhibitors, serotonin (5-HT), and citalopram. Like CEE, SPE increased TPH protein levels. Social subordinates had markedly lower TPH protein levels than dominants regardless of hormone replacement. Therefore, these two variables had independent and additive effects. CEE and SPE increased SERT, and social status had no effect. Thus, the hormone-induced increase in SERT was accompanied by increased 5-HT synthesis and neuronal firing, which appears biologically reasonable as 5-HT prevented SERT degradation in vitro.