The augmentation hypothesis for improvement of antidepressant therapy: is pindolol a suitable candidate for testing the ability of 5HT1A receptor antagonists to enhance SSRI efficacy and onset latency?

Mobile cognitive behavioral therapy for insomnia: analysis of factors affecting treatment prognosis

This study aims to explore the factors that affect the prognosis of patients with insomnia who are treated with mobile cognitive behavioral therapy. Patients with insomnia who visited the sleep disorders clinic were selected and completed mobile Cognitive behavioral therapy. Patients completed at least three evaluations (including baseline, monthly evaluations thereafter, and a final evaluation at the end of one year) and responded well to treatment within one year of follow-up. Insomnia, anxiety, and depression symptoms were evaluated using the Pittsburgh Sleep Quality Index (PSQI), the Generalized Anxiety Disorder 7-item (GAD-7) scale, and the 9-item Patient Health Questionnaire (PHQ-9), respectively. Treatment prognosis including relapse, recurrence, and remission group. These 339 patients were divided into three groups: 160 patients who remission, 100 patients who relapsed, and 79 patients who experienced recurrence after remission. Demographic characteristics of the 339 patients showed no significant difference in gender between the three groups (P = 0.978). However, significant differences were found in age (P = 0.006) and onset time (P = 0.000) among the three groups. The remission group had a higher average age than the recurrence group and the relapse group, and the onset time was slower than the other two groups. Multivariate logistic regression analysis showed that age and delayed onset time were protective factors for good treatment prognosis, while low educational level and high GAD-7 scores were independent risk factors for poor prognosis. There are many factors that affect the treatment prognosis of insomnia. Age, low educational level, high GAD-7 scores, and delayed onset time can be used to predict the prognosis of insomnia treatment.

Protective effects of SSRI, Citalopram in mutant APP and mutant Tau expressed dorsal raphe neurons in Alzheimer's disease

Depression is among the most common neuropsychiatric comorbidities in Alzheimer's disease (AD) and other Tauopathies. Apart from its anti-depressive and anxiolytic effects, selective serotonin reuptake inhibitor (SSRI) treatment also offers intracellular modifications that may help to improve neurogenesis, reduce amyloid burden & Tau pathologies, and neuroinflammation in AD. Despite its multifaceted impact in the brain, the exact physiological and molecular mechanism by which SSRIs such as Citalopram improve neurogenesis and synaptogenesis in dementia is poorly understood. In the current study, we investigated the protective role of SSRI, Citalopram, in serotonergic, medullary raphe neurons (RN46A-B14). RN46A-B14 cells were transfected with wild-type and mutant APP and Tau cDNAs for 24 h and then treated with 20 μM Cit for 24 h. We then assessed mRNA and protein levels of pTau, total Tau, serotonin related proteins such as TPH2, SERT, and 5HTR1a, synaptic proteins and the cytoskeletal structure. We also assessed cell survival, mitochondrial respiration and mitochondrial morphology. The mutant APP and Tau transfected cells showed increased levels of serotonin related proteins and mRNA, while the mRNA and protein levels of synaptic proteins were downregulated. Citalopram treatment significantly reduced pathologically pTau level along with the serotonin related protein levels. On the other hand, there was a significant increase in the mRNA and protein levels of synaptic genes and cytoskeletal structure in the treated groups. Further, Citalopram also improved cell survival, mitochondrial respiration and mitochondrial morphology in the treated cells that express mAPP and mTau. Taken together these findings suggest Citalopram could not only be a promising therapeutic drug for treating patients with depression, but also for AD patients.

Beyond sports: Efficacy and safety of creatine supplementation in pathological or paraphysiological conditions of brain and muscle

Creatine is pivotal in energy metabolism of muscle and brain cells, both in physiological and in pathological conditions. Additionally, creatine facilitates the differentiation of muscle and neuronal cells. Evidence of effectiveness of creatine supplementation in improving several clinical conditions is now substantial, and we review it in this paper. In hereditary diseases where its synthesis is impaired, creatine has a disease-modifying capacity, especially when started soon after birth. Strong evidence, including a Cochrane meta-analysis, shows that it improves muscular strength and general well-being in muscular dystrophies. Significant evidence exists also of its effectiveness in secondary prevention of statin myopathy and of treatment-resistant depression in women. Vegetarians and vegans do not consume any dietary creatine and must synthesize all they need, spending most of their methylation capacity. Nevertheless, they have a lower muscular concentration of creatine. Creatine supplementation has proved effective in increasing muscular and neuropsychological performance in vegetarians or vegans and should, therefore, be recommended especially in those of them who are athletes, heavy-duty laborers or who undergo intense mental effort. Convincing evidence also exists of creatine effectiveness in muscular atrophy and sarcopenia in the elderly, and in brain energy shortage (mental fatigue, sleep deprivation, environmental hypoxia as in mountain climbing, and advanced age). Furthermore, we review more randomized, placebo-controlled trials showing that creatine supplementation is safe up to 20 g/d, with a possible caveat only in people with kidney disease. We trust that the evidence we review will be translated into clinical practice and will spur more research on these subjects.

Citalopram plus low-dose pipamperone versus citalopram plus placebo in patients with major depressive disorder: an 8-week, double-blind, randomized study on magnitude and timing of clinical response

BACKGROUND

Selective serotonin reuptake inhibitors take several weeks to achieve their full antidepressant effects. Post-synaptic 5-HT2A receptor activation is thought to be involved in this delayed therapeutic effect. Pipamperone acts as a highly selective 5-HT2A/D4 antagonist when administered in low doses. The purpose of this study was to compare citalopram 40 mg once daily plus pipamperone 5 mg twice daily (PipCit) versus citalopram plus placebo twice daily for magnitude and onset of therapeutic effect.

METHOD

An 8-week, randomized, double-blind study in patients with major depressive disorder was carried out.

RESULTS

The study population comprised 165 patients (citalopram and placebo, n=82; PipCit, n=83) with a mean baseline Montgomery-Asberg Depression Rating Scale (MADRS) score of 32.6 (s.d.=5.5). In the first 4 weeks, more citalopram and placebo than PipCit patients discontinued treatment (18% v. 4%, respectively, p=0.003). PipCit patients had significantly greater improvement in MADRS score at week 1 [observed cases (OC), p=0.021; last observation carried forward (LOCF), p=0.007] and week 4 (LOCF, p=0.025) but not at week 8 compared with citalopram and placebo patients. Significant differences in MADRS scores favoured PipCit in reduced sleep, reduced appetite, concentration difficulties and pessimistic thoughts. Mean Clinical Global Impression-Improvement scores were significantly improved after 1 week of PipCit compared with citalopram and placebo (OC and LOCF, p=0.002).

CONCLUSIONS

Although the MADRS score from baseline to 8 weeks did not differ between groups, PipCit provided superior antidepressant effects and fewer discontinuations compared with citalopram and placebo during the first 4 weeks of treatment, especially in the first week.

Fluoxetine administration to pregnant rats increases anxiety-related behavior in the offspring

RATIONALE

Fluoxetine (Prozac®) is the most frequently prescribed drug to battle depression in pregnant women, but its safety in the unborn child has not yet been established. Fluoxetine, a selective serotonin reuptake inhibitor, crosses the placenta, leading to increased extracellular serotonin levels and potentially neurodevelopmental changes in the fetus.

OBJECTIVES

The purpose of this study was to elucidate the long-term consequences of prenatal fluoxetine in rats.

METHODS

Pregnant rats were injected daily with 12 mg/kg fluoxetine or vehicle from gestational day 11 until birth, and the behavior of the offspring was monitored.

RESULTS

Plasma fluoxetine transfer from mother to pup was 83%, and high levels of fluoxetine (13.0 μg/g) were detected in the pup brain 5 h after the last injection. Fluoxetine-treated dams gave birth to litters 15% smaller than usual and to pups of reduced weight (until postnatal day 7). Furthermore, prenatal fluoxetine exposure significantly increased anxiety in the novelty-suppressed feeding test, the footshock-induced conditioned place aversion test, and the elevated plus maze test (following footshock pre-exposure) during adulthood, and also significantly decreased components of social play behavior at 4 weeks of age, and a strong tendency for increased self-grooming and making less contact in adults. Behavioral despair, anhedonia, and sexual behavior were not different between treatment groups. Finally, the hypothermic response to the 5-HT(1A) agonist flesinoxan was observed at a lower dose in prenatally fluoxetine-exposed rats than in controls.

CONCLUSIONS

Prenatal fluoxetine exposure in rats leads to detrimental behavioral outcomes in later life, which may partly be due to altered 5-HT(1A) receptor signaling.

Neurosteroids as neuromodulators in the treatment of anxiety disorders

Anxiety disorders are the most common psychiatric disorders. They are frequently treated with benzodiazepines, which are fast acting highly effective anxiolytic agents. However, their long-term use is impaired by tolerance development and abuse liability. In contrast, antidepressants such as selective serotonin reuptake inhibitors (SSRIs) are considered as first-line treatment but have a slow onset of action. Neurosteroids are powerful allosteric modulators of GABA(A) and glutamate receptors. However, they also modulate sigma receptors and they are modulated themselves by SSRIs. Both pre-clinical and clinical studies have shown that neurosteroid homeostasis is altered in depression and anxiety disorders and antidepressants may act in part through restoring neurosteroid disbalance. Moreover, novel drugs interfering with neurosteroidogenesis such as ligands of the translocator protein (18 kDa) may represent an attractive pharmacological option for novel anxiolytics which lack the unwarranted side effects of benzodiazepines. Thus, neurosteroids are important endogenous neuromodulators for the physiology and pathophysiology of anxiety and they may constitute a novel therapeutic approach in the treatment of these disorders.

The putative antidepressant DOV 216,303, a triple reuptake inhibitor, increases monoamine release in the prefrontal cortex of olfactory bulbectomized rats

The first line of antidepressant treatment nowadays are selective serotonin reuptake inhibitors. Although they are relatively safe to use, selective serotonin reuptake inhibitors (SSRIs) can induce severe side effects. New promising antidepressants may be the triple monoamine reuptake inhibitors, which not only enhance serotonin and norepinephrine neurotransmission, but also increase brain dopamine levels. Recently it has been shown that one of the triple reuptake inhibitors, DOV 216,303 has antidepressant-like effects in the olfactory bulbectomy (OBX) model of depression, but the alterations in monoaminergic neurotransmission in these animals are still unknown. In the present study we investigated not only the effect of acute, but also chronic treatment of DOV 216,303 in OBX rats on monoamine and metabolite levels. The main results are decreased baseline dopamine levels in the prefrontal cortex one day after OBX, while 38days after OBX no difference could be observed in monoamine levels after vehicle treatment. Treatment with DOV 216,303 leads to increased extracellular levels of serotonin and norepinephrine neurotransmission, but also increased dopamine levels in OBX animals as well as their controls. This increase could be observed after one single administration, but also after chronic treatment. However, a DOV 216,303 challenge in chronically treated animals resulted in lower monoamine concentrations than the same challenge in untreated animals. More research is needed to investigate this seemingly hyporesponsivity to chronic DOV 216,303 treatment.

Strategy to Accelerate or Augment the Antidepressant Response and for An Early Onset of SSRI Activity. Adjunctive Amisulpride to Fluvoxamine in Major Depressive Disorder

The topic of early response to antidepressant treatment has been extensively studied in major depressive disorder (MDD). We serendipitous observed an increase tolerability, a rapid response to therapy and an early onset of antidepressant fluvoxamine activity when associated with amisulpride in patients with major depressive disorder. The purpose of this study was to investigate our preliminary observations.

A regulatory domain in the N terminus of tryptophan hydroxylase 2 controls enzyme expression

Serotonin is involved in a variety of physiological processes in the central nervous system and the periphery. As the rate-limiting enzyme in serotonin synthesis, tryptophan hydroxylase plays an important role in modulating these processes. Of the two variants of tryptophan hydroxylase, tryptophan hydroxylase 2 (TPH2) is expressed predominantly in the central nervous system, whereas tryptophan hydroxylase 1 (TPH1) is expressed mostly in peripheral tissues. Although the two enzymes share considerable sequence homology, the regulatory domain of TPH2 contains an additional 41 amino acids at the N terminus that TPH1 lacks. Here we show that the extended TPH2 N-terminal domain contains a unique sequence involved in the regulation of enzyme expression. When expressed in cultured mammalian cells, TPH2 is synthesized less efficiently and is also less stable than TPH1. Removal of the unique portion of the N terminus of TPH2 results in expression of the enzyme at a level similar to that of TPH1, whereas protein chimeras containing this fragment are expressed at lower levels than their wild-type counterparts. We identify a region centered on amino acids 10-20 that mediates the bulk of this effect. We also demonstrate that phosphorylation of serine 19, a protein kinase A consensus site located in this N-terminal domain, results in increased TPH2 stability and consequent increases in enzyme output in cell culture systems. Because this domain is unique to TPH2, these data provide evidence for selective regulation of brain serotonin synthesis.

Animal models and treatments for addiction and depression co-morbidity

The high rates of co-morbidity of drug addiction with depression may be attributable to shared neurobiology. Here, we discuss shared neurobiological substrates in drug withdrawal and depression, with an emphasis on changes in brain reward circuitry that may underlie anhedonia, a core symptom of depression and drug withdrawal. We explored experimentally whether clinical antidepressant medications or other treatments would reverse the anhedonia observed in rats undergoing spontaneous nicotine or amphetamine withdrawal, defined operationally as elevated brain reward thresholds. The co-administration of selective serotonin reuptake inhibitors with a serotonin-1A receptor antagonist, or the tricyclic antidepressant desipramine, or the atypical antidepressant bupropion ameliorated nicotine or amphetamine withdrawal in rats. Thus, increases in monoaminergic neurotransmission, or neuroadaptations induced by increased monoaminergic neurotransmission, ameliorated depression-like aspects of drug withdrawal. Further, chronic pretreatment with the atypical antipsychotic clozapine, that has some efficacy in the treatment of the depression-like symptoms of schizophrenia, attenuated nicotine and amphetamine withdrawal. Finally, a metabotropic glutamate 2/3 receptor antagonist reversed threshold elevations associated with nicotine withdrawal. The effects of these pharmacological manipulations are consistent with the altered neurobiology observed in drug withdrawal and depression. Thus, these data support the hypothesis of common substrates mediating the depressive symptoms of drug withdrawal and those seen in psychiatric patients. Accordingly, the anhedonic state associated with drug withdrawal can be used to study the neurobiology of anhedonia, and thus contribute to the identification of novel targets for the treatment of depression-like symptoms seen in various psychiatric and neurological disorders.

Antidepressant-like effects of Albizzia julibrissin in mice: Involvement of the 5-HT1A receptor system

The present study was undertaken to investigate the antidepressant-like effects of the methylene chloride fraction of Albizzia julibrissin (MCAJ) using a tail suspension test in mice. MCAJ was orally administered at 50, 100, or 200 mg/kg to mice, 1 h before the tail suspension test. Acute treatment with MCAJ at 200 mg/kg significantly reduced the immobility time compared with the control group, and thus showed an antidepressant-like effect. This effect was comparable to that of imipramine at 10 mg/kg. This antidepressant-like effect was reversed by treatment with WAY-100635 (a 5-HT1A receptor antagonist) or pindolol (a 5-HT1A/1B receptor antagonist). However, the antidepressant effect of MCAJ was not effected by treatment with GR55562 (a 5-HT1B receptor antagonist) or ketanserin (a 5-HT2A receptor antagonist). Therefore, our findings suggest that MCAJ exerts its antidepressant-like effect via the 5-HT1A receptor system.

Comorbidity of substance abuse with other psychiatric disorders

Substance abuse is a frequent comorbid condition with other psychiatric disorders including schizophrenia and depression. These disorders may share a common substrate at the neurotransmitter or neurocircuit level. One candidate is hypofunction of the glutamate system. Several lines of evidence suggest that N-methyl-D-aspartate (NMDA) receptors may hypofunction in schizophrenia. Thus, NMDA receptor antagonists are schizophrenogenic; postmortem and imaging results point to reduced NMDA receptor function in schizophrenic brains; a number of genes that have been linked to schizophrenia code for proteins that influence NMDA function; and there is preliminary evidence that pro-NMDA drugs may be therapeutic in the treatment of schizophrenia. One of the most effective therapeutics for the treatment of substance abuse in schizophrenic people is clozapine, and clozapine may act at the glycine modulatory site to enhance NMDA receptor function. This preliminary line of evidence may link schizophrenia and drug abuse to a common neurochemical base, subnormal NMDA receptor function. People with schizophrenia and drug abusers similarly show deficits in tasks known to be sensitive to ventromedial prefrontal cortical damage, and both groups show decreased activation in the ventral striatum during reward anticipation in functional magnetic resonance imaging studies. These observations implicate common prefrontal cortical-striatal circuits and their modulation by hippocampal projections in schizophrenia and substance abuse. Withdrawal from substance abuse and depression both have been linked to changes in the function of several neurotransmitters including serotonin, dopamine and glutamate. These findings suggest possible common substrates and novel therapeutic approaches. Further studies are needed to fully characterize the neurocircuits and transmitters involved in various psychiatric disorders and their possible common elements in comorbid drug abuse.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Maternal separation alters serotonergic transporter densities and serotonergic 1A receptors in rat brain

RATIONALE

The basic mechanisms underlying the association between early life maternal separation and adulthood psychiatric disorders are largely unknown. One possible candidate is the central serotonergic system, which is also abnormal in psychiatric illnesses. Neuroadaptational changes in serotonergic transporter and serotonergic 1A receptors may underlie links between early life stress and adulthood psychiatric disorders.

OBJECTIVE

The aim of this study was to investigate the consequences of a rat model of maternal separation on serotonergic transporter and serotonergic 1A receptor densities and function in adult rat forebrain.

METHODS

Rat pups were separated from dams from postnatal day 2 to postnatal day 14, each day, for zero time, 15 min and 180 min to determine the time-course of effects. A non-handled group was added to control for the effects of handling by an experimenter compared with the animal facility-reared group. Quantitative [(125)I]3beta-(4-iodophenyl)tropan-2beta-carboxylic acid methyl ester and [(125)I]-mPPI autoradiography was used to determine serotonergic transporter and serotonergic 1A densities, respectively. Adult rats were challenged with saline or serotonergic 1A agonist (+) 8-hydroxy-2-(di-n-propylamino)tetralin, 0.4 mg/kg, s.c.) and plasma adrenocorticotropic hormone and corticosterone were determined.

RESULTS

serotonergic transporter and serotonergic 1A densities were significantly lower in the non-handled group in the paraventricular, arcuate, dorsomedial and ventromedial nuclei of the hypothalamus. The non-handled group also displayed lower serotonergic transporter and serotonergic 1A densities in the basolateral anterior, basolateral ventral and basomedial amygdaloid nuclei. Serotonergic transporter densities were also decreased in the CA3 area of the hippocampus in the non-handled group. In contrast, the maternal separation 15 min group displayed the highest serotonergic transporter and serotonergic 1A densities in the basomedial nucleus of amygdala, basolateral anterior nucleus of amygdala, basolateral ventral nucleus of amygdala and basomedial nucleus of amygdala amygdaloid nuclei.

CONCLUSIONS

Early life maternal separation and the extent of handling can alter adult brain serotonergic transporter and serotonergic 1A levels and function in the forebrain. Alterations in these serotonergic systems by early rearing conditions might increase vulnerability for behavioral disorders in adulthood.

Antidepressant effects assessed using behavior maintained under a differential-reinforcement-of-low-rate (DRL) operant schedule

Behavior maintained under a differential-reinforcement-of-low-rate (DRL) 72-s operant schedule, which reinforces responses with interresponse times greater than 72 s, exhibits a rather unique sensitivity to antidepressant drugs. Antidepressants from a number of pharmacological classes, including tricyclic antidepressants, selective serotonin or norepinephrine reuptake inhibitors, monoamine oxidase inhibitors, as well as a number of atypical antidepressants and putative antidepressants, reduce response rate and increase reinforcement rate of rats under this schedule. These effects are observed acutely but persist or are augmented with repeated treatment. By contrast, drugs from a number of other psychotherapeutic classes do not, in general, produce similar effects. This includes anxiolytic, sedative, stimulant, opioid, antihistaminic, and anticholinergic drugs, which can produce false positive results in some preclinical tests for antidepressant efficacy. There are conflicting data regarding the utility of DRL behavior for discriminating the effects of antidepressant and antipsychotic drugs. This results in part from methodological differences among studies, but likely also reflects the overlap between the neuropharmacological and clinical effects of some antipsychotic and antidepressant drugs. DRL behavior also has proven useful for identifying neurochemical and neuroanatomical mediators of antidepressant effects on behavior. Consistent with clinical data, it appears that activation of noradrenergic or serotonergic systems provides for parallel means of producing antidepressant-like effects on DRL behavior. Finally, the results of studies using DRL behavior highlight important roles for central beta-1 adrenergic receptors, as well as 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT2C receptors, in the mediation of antidepressant-like behavioral effects.

The role of monoamines in the actions of established and "novel" antidepressant agents: a critical review

Monoaminergic pathways are highly responsive to aversive stimuli and play a crucial role in the control of affect, cognition, endocrine secretion, chronobiotic rhythms, appetite, and motor function, all of which are profoundly disrupted in depressive states. Accordingly, a perturbation of monoaminergic transmission is implicated in the aetiology of depressive disorders, and all clinically available antidepressants increase corticolimbic availability of monoamines. However, their limited efficacy, delayed onset of action, and undesirable side effects underlie ongoing efforts to identify improved therapeutic agents. Sequencing the human genome has raised the hope not only of better symptomatic control of depression, but even of the prevention or cure of depressive states. In the pursuit of these goals, there is currently a tendency to focus on selective ligands of "novel" nonmonoaminergic targets. However, certain classes of novel agent (such as neurokinin(1) receptor antagonists) indirectly modulate the activity of monoaminergic networks. Others may act "downstream" of them, converging onto common cellular substrates controlling gene expression, synaptic plasticity, and neurogenesis. Further, by analogy to the broad-based actions of currently employed drugs, multitarget agents may be better adapted than selective agents to the management of depression-a complex disorder with hereditary, developmental, and environmental origins. It is, thus, important to continue the creative exploration of clinically validated and innovative monoaminergic strategies within a multitarget framework. In this light, drugs combining monoaminergic and nonmonoaminergic mechanisms of action may be of particular interest. The present article provides a critical overview of monoaminergic strategies for the treatment of depressive states, both established and under development, and discusses interactions of novel "nonmonoaminergic" antidepressants with monoaminergic mechanisms.

Retinal serotonin, eye growth and myopia development in chick

Myopia (short-sightedness) is a visual problem associated with excessive eye growth and vitreous chamber expansion. Within the eye serotonin (5-hydroxytryptamine, 5-HT) appears to have a variety of effects, it alters retinal amacrine cell processing, increases intraocular pressure, constricts ocular blood vessels, and is also mitogenic. This study sought to determine the role of the retinal serotonin system in eye growth regulation. Myopia was produced in 7-day-old chicks using -15 D spectacle lenses (LIM) and form deprivation (FDM). The effect on LIM and FDM of daily intravitreal injections of a combination of 5-HT receptor antagonists (1, 10, 50 microM), 5-HT(2) selective antagonist (Mianserin 0.5, 20 microM) or 5-HT (1, 10, 50 microM) were assessed. Counts were performed of serotonin and tyrosine hydroxylase positive neurons and the relative density used to account for areal changes due to eye growth. The effect of LIM and lens-induced hyperopia (LIH) on the numbers of 5-HT-containing amacrine cells in the retina were then determined. The combination of 5-HT receptor antagonists inhibited LIM by approximately half (1 microM RE: -7.12+/-1.0 D, AL: 0.38+/-0.06 mm vs. saline RE: -13.19+/-0.65 D, AL: 0.64+/-0.03 mm. RE: p<0.01, AL: p<0.01), whereas FDM was not affected (1 microM RE: -8.88+/-1.10 D vs. saline RE: -9.28+/-1.38 D). The selective antagonist was slightly less effective at inhibiting LIM (0.5 microM RE: -9.02+/-1.01 D). These data suggest that serotonin has a stimulatory role in LIM, although high doses of serotonin were inhibitory (1 microM RE: -9.30+/-1.34 D). 5-HT immunoreactivity was localised to a subset of amacrine cell bodies in the inner nuclear layer of the retina, and to two synaptic strata in the inner plexiform layer. LIM eyes had increased numbers of 5-HT-containing amacrine cells in the central retina (12.5%). Collectively, these results suggest that manipulations to the serotonin system can alter the eye growth process but the role of this transmitter system within this process remains unclear.

Effectiveness of pindolol plus serotonin uptake inhibitors in depression: a meta-analysis of early and late outcomes from randomised controlled trials

BACKGROUND

Contradictory results on the efficacy of pindolol associated with selective serotonin reuptake inhibitors (SSRIs) in depressive illness have been published and no former review has produced an overall figure of its efficacy. This study aims to review the efficacy and tolerability of pindolol plus SSRIs in depressive illness.

METHODS

A meta-analysis of randomised controlled trials (RCTs) comparing pindolol plus SSRIs with placebo plus SSRIs.

RESULTS

Nine RCTs met inclusion criteria. Outcome favoured pindolol at 2 weeks time (N=5; OR=2.8; 95% CI 1.4-5.7), but not at four to 6 weeks (N=7; OR=1.4; 95% CI 0.8-2.7). Results for early outcome studies were robust to sensitivity analysis. Nineteen more studies, averaging null results, would be needed to change the overall probability (P=0.0001) to a non-significant figure.

CONCLUSIONS

Pindolol seems to hasten the response to SSRIs in depression with a timing window circumscribed to the first weeks of treatment.

Sex hormone-dependent desensitization of 5-HT1A autoreceptors in knockout mice deficient in the 5-HT transporter

The serotonin transporter (5-HTT) is the target of most antidepressant drugs, whose therapeutic action is related to their facilitatory influence on 5-HT neurotransmission. In this study, we investigated the functional adaptive properties of 5-HT1A autoreceptors, which regulate serotonergic neuronal firing, in knockout mice deficient in 5-HTT. Neurons of the dorsal raphe nucleus (DRN) were recorded extracellularly under chloral hydrate anaesthesia in male and female knockout 5-HTT mice and their wild-type counterparts. The inhibitory response of DRN neurons to intravenous injection of the 5-HT1A agonist 8-OH-DPAT was dramatically reduced in knockout 5-HTT compared with wild-type mice, especially in females. Changes in 8-OH-DPAT-induced hypothermia and autoradiographic labelling of 5-HT1A sites in the DRN confirmed a greater level of desensitization/down-regulation of 5-HT1A autoreceptors in female than in male knockout 5-HTT mice. After gonadectomy, the functional status of 5-HT1A autoreceptors was unchanged in wild-type mice, whereas in knockout 5-HTT, castrated males exhibited a down-regulation, and ovariectomized females an up-regulation of these receptors, as shown by electrophysiological recording and autoradiographic labelling in the DRN, as well as by changes in 8-OH-DPAT-induced hypothermia. Finally, in gonadectomized knockout 5-HTT mice, treatment with testosterone or estradiol restored the DRN neuronal firing sensitivity to 8-OH-DPAT back to sham control level in males or females, respectively. These data indicate that sexual hormones participate in the mechanisms responsible for the desensitization of 5-HT1A autoreceptors in knockout 5-HTT mice. The differential effects of testosterone and estradiol on 5-HT1A-mediated control of 5-HT neurotransmission might be related to the well-established gender differences in the vulnerability to depression.

5-HT(1A) receptor subsensitivity in infancy and supersensitivity in adulthood in an animal model of depression

Flinders Sensitive Line (FSL) rats, a genetic animal model of depression, exhibit 5-HT abnormalities including an increased sensitivity to serotonergic agonists. Studies of 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT)-induced hypothermia have shown 5-HT(1A) receptor supersensitivity in adult FSL rats. The aims of the present study were to: (a) further characterize the 5-HT(1A) system in adult FSL rats by assessing their behavioral responses to 8-OH-DPAT (the 'serotonergic syndrome'-a pattern of stereotypic behavior on a number of parameters). (b) Examine behavioral and hypothermic responses of neonatal FSL pups to 8-OH-DPAT. In adult FSL rats the 'serotonergic syndrome' was measured (Exp. 1) and in 1-day-old pups body temperature and ultrasonic vocalizations (USV) were also examined (Exp. 2) following administration (s.c. and i.p., respectively) of 8-OH-DPAT (1 mg/kg). Overall, adult FSL rats exhibited a significant supersensitive behavioral response to 8-OH-DPAT compared to Sprague-Dawley controls. Under baseline conditions, body weight, USV and rectal temperature were significantly lower in FSL pups compared to controls. In contrast to the adults, 1-day-old FSL pups exhibited an overall pattern of subsensitive stereotypic response to the agonist. In conclusion, an abnormal pattern of response to 8-OH-DPAT was observable in FSL rats, as early as postnatal day 1. This may contribute to a better understanding of the involvement of the serotonergic system in depression, and lead to pharmacological interventions aiming to modulate 5-HT regulation.

Synergistic action of 5-HT2A antagonists and selective serotonin reuptake inhibitors in neuropsychiatric disorders

Recently, the addition of drugs with prominent 5-HT(2) receptor antagonist properties (risperidone, olanzapine, mirtazapine, and mianserin) to selective serotonin reuptake inhibitors (SSRIs) has been shown to enhance therapeutic responses in patients with major depression and treatment-refractory obsessive-compulsive disorder (OCD). These 5-HT(2) antagonists may also be effective in ameliorating some symptoms associated with autism and other pervasive developmental disorders (PDDs). At the doses used, these drugs would be expected to saturate 5-HT(2A) receptors. These findings suggest that the simultaneous blockade of 5-HT(2A) receptors and activation of an unknown constellation of other 5-HT receptors indirectly as a result of 5-HT uptake inhibition might have greater therapeutic efficacy than either action alone. Animal studies have suggested that activation of 5-HT(1A) and 5-HT(2C) receptors may counteract the effects of activating 5-HT(2A) receptors. Additional 5-HT receptors, such as the 5-HT(1B/1D/5/7) receptors, may similarly counteract the effects of 5-HT(2A) receptor activation. These clinical and preclinical observations suggest that the combination of highly selective 5-HT(2A) antagonists and SSRIs, as well as strategies to combine high-potency 5-HT(2A) receptor and 5-HT transporter blockade in a single compound, offer the potential for therapeutic advances in a number of neuropsychiatric disorders.

Internalization and recycling of 5-HT2A receptors activated by serotonin and protein kinase C-mediated mechanisms

Serotonin (5-HT), a major neurotransmitter, has a large number of G protein-coupled receptors in mammals. On activation by exposure to their ligand, 5-HT(2) receptor subtypes increase IP(3) levels and undergo desensitization and internalization. To visualize the receptor in cells during these processes, we have constructed a 5-HT(2A)-enhanced GFP (SR2-GFP) fusion receptor. We show that this fusion receptor undergoes internalization on exposure to its natural ligand, 5-HT. Because 5-HT(2A) receptors activate the phospholipase C pathway, we studied the effect of protein kinase C (PKC) on the internalization process and found that activation of PKC by its specific activator phorbol 12-myristate 13-acetate, in the absence of 5-HT, leads to internalization of the receptor. Moreover, inhibition of PKC by its inhibitor sphingosine in the presence of 5-HT prevents the internalization process, suggesting that activation of PKC is sufficient and necessary for the internalization of 5-HT(2A) receptors. We also show that SR2-GFP recycles back to the plasma membrane after 5-HT-dependent internalization, suggesting a mechanism for resensitization. In addition, receptors that have been internalized on addition of phorbol 12-myristate 13-acetate in the absence of 5-HT also recycle to the surface, with a time course similar to that seen after activation of the receptors by 5-HT. Our study suggests that 5-HT(2A) receptors internalize and return to the surface after both serotonin- and PKC-mediated processes. This study reveals a role for PKC in receptor internalization and also shows that 5-HT(2A) receptors are recycled.