5-HT(1A) receptor dysfunction in female patients with schizophrenia

The risk factors, frequency and diagnosis of atypical antipsychotic drug-induced hypothermia: practical advice for doctors

Hypothermia is unpredictable and life-threatening adverse effect of atypical antipsychotic drug (APD) treatment, which has been little described. The aim of this article is to increase the awareness that hypothermia induced by APD drugs is more common than the current published case reports may suggest, and risk factors increase its development. Moreover, valuable guidelines regarding how to detect the early stages of hypothermia in clinical practice are included. A literature search for reports on APD-induced hypothermia in PubMed, Academic Search Complete, Medline Complete and eHealthMe databases was conducted. The literature search apart from eHealthMe database resulted in 524 articles, which included 34 case reports. Hypothermia was mostly induced by olanzapine (14) and risperidone (10). However, the data from Food and Drug Administration reports revealed several dozen more cases of APD-induced hypothermia (591case reports) compared with the published case reports (e.g. olanzapine-262 and risperidone-161). Hypothermia, mostly mild (61% of cases), has developed mainly in men (71%) having schizophrenia, a few hours after commencement of treatment or in the presence of risk factors. Owing to the increased risk of hypothermia development during APD treatment, doctors should routinely measure body temperature of patients, especially during the first days of the therapy. Early diagnosis of hypothermia and appropriate treatment may prevent death.

Common and distinct brain networks underlying panic and social anxiety disorders

Although panic disorder (PD) and phobic disorders are independent anxiety disorders with distinct sets of diagnostic criteria, there is a high level of overlap between them in terms of pathogenesis and neural underpinnings. Functional connectivity research using resting-state functional magnetic resonance imaging (rsfMRI) shows great potential in identifying the similarities and differences between PD and phobias. Understanding common and distinct networks between PD and phobic disorders is critical for identifying both specific and general neural characteristics of these disorders. We review recent rsfMRI studies and explore the clinical relevance of resting-state functional connectivity (rsFC) in PD and phobias. Although findings differ between studies, there are some meaningful, consistent findings. Social anxiety disorder (SAD) and PD share common default mode network alterations. Alterations within the sensorimotor network are observed primarily in PD. Increased connectivity in the salience network is consistently reported in SAD. This review supports hypotheses that PD and phobic disorders share common rsFC abnormalities and that the different clinical phenotypes between the disorders come from distinct brain functional network alterations.

Serotonergic modulation of resting state default mode network connectivity in healthy women

The default mode network (DMN) plays a central role in intrinsic thought processes. Altered DMN connectivity has been linked to diminished cerebral serotonin synthesis. Diminished brain serotonin synthesis is further associated with a lack of impulse control and various psychiatric disorders. Here, we investigated the serotonergic modulation of intrinsic functional connectivity (FC) within the DMN in healthy adult females, controlling for the menstrual cycle phase. Eighteen healthy women in the follicular phase (aged 20-31 years) participated in a double-blind controlled cross-over study of serotonin depletion. Acute tryptophan depletion (ATD) and a balanced amino acid load (BAL), used as the control condition, were applied on two separate days of assessment. Neural resting state data using functional magnetic resonance imaging (fMRI) and individual trait impulsivity scores were obtained. ATD compared with BAL significantly reduced FC with the DMN in the precuneus (associated with self-referential thinking) and enhanced FC with the DMN in the frontal cortex (associated with cognitive reasoning). Connectivity differences with the DMN between BAL and ATD in the precentral gyrus were significantly correlated with the magnitude of serotonin depletion. Right medial frontal gyrus and left superior frontal gyrus connectivity differences with the DMN were inversely correlated with trait impulsivity. These findings partially deviate from previous findings obtained in males and underline the importance of gender-specific studies and controlling for menstrual cycle to further elucidate the mechanism of ATD-induced changes within intrinsic thought processes.

Sex differences in the HPA axis

The hypothalamic-pituitary-adrenal (HPA) axis is a major component of the systems that respond to stress, by coordinating the neuroendocrine and autonomic responses. Tightly controlled regulation of HPA responses is critical for maintaining mental and physical health, as hyper- and hypo-activity have been linked to disease states. A long history of research has revealed sex differences in numerous components of the HPA stress system and its responses, which may partially form the basis for sex disparities in disease development. Despite this, many studies use male subjects exclusively, while fewer reports involve females or provide direct sex comparisons. The purpose of this article is to present sex comparisons in the functional and molecular aspects of the HPA axis, through various phases of activity, including basal, acute stress, and chronic stress conditions. The HPA axis in females initiates more rapidly and produces a greater output of stress hormones. This review focuses on the interactions between the gonadal hormone system and the HPA axis as the key mediators of these sex differences, whereby androgens increase and estrogens decrease HPA activity in adulthood. In addition to the effects of gonadal hormones on the adult response, morphological impacts of hormone exposure during development are also involved in mediating sex differences. Additional systems impinging on the HPA axis that contribute to sex differences include the monoamine neurotransmitters norepinephrine and serotonin. Diverse signals originating from the brain and periphery are integrated to determine the level of HPA axis activity, and these signals are, in many cases, sex-specific.

Morning cortisol levels in schizophrenia and bipolar disorder: a meta-analysis

Increased peripheral levels of morning cortisol have been reported in people with schizophrenia (SZ) and bipolar disorder (BD), but findings are inconsistent and few studies have conducted direct comparisons of these disorders. We undertook a meta-analysis of studies examining single measures of morning cortisol (before 10 a.m.) levels in SZ or BD, compared to controls, and to each other; we also sought to examine likely moderators of any observed effects by clinical and demographic variables. Included studies were obtained via systematic searches conducted using Medline, BIOSIS Previews and Embase databases, as well as hand searching. The decision to include or exclude studies, data extraction and quality assessment was completed in duplicate by LG, SM and AS. The initial search revealed 1459 records. Subsequently, 914 were excluded on reading the abstract because they did not meet one or more of the inclusion criteria; of the remaining 545 studies screened in full, included studies were 44 comparing SZ with controls, 19 comparing BD with controls, and 7 studies directly comparing schizophrenia with bipolar disorder. Meta-analysis of SZ (N=2613, g=0.387, p=0.001) and BD (N=704, g=0.269, p=0.004) revealed moderate quality evidence of increased morning cortisol levels in each group compared to controls, but no difference between the two disorders (N=392, g=0.038, p=0.738). Subgroup analyses revealed greater effect sizes for schizophrenia samples with an established diagnosis (as opposed to 'first-episode'), those that were free of medication, and those sampled in an inpatient setting (perhaps reflecting an acute illness phase). In BD, greater morning cortisol levels were found in outpatient and non-manic participants (as opposed to those in a manic state), relative to controls. Neither age nor sex affected cortisol levels in any group. However, earlier greater increases in SZ morning cortisol were evident in samples taken before 8 a.m. (relative to those taken after 8 a.m.). Multiple meta-regression showed that medication status was significantly associated with morning cortisol levels in SZ, when the effects of assay method, sampling time and illness stage were held constant. Heightened levels of morning cortisol in SZ and BD suggest long-term pathology of the hypothalamic-pituitary-adrenal (HPA) axis that may reflect a shared process of illness development in line with current stress-vulnerability models.

Neuroprogression in schizophrenia: Pathways underpinning clinical staging and therapeutic corollaries

OBJECTIVE

Whilst dopaminergic dysfunction remains a necessary component involved in the pathogenesis of schizophrenia, our current pharmacological armoury of dopamine antagonists does little to control the negative symptoms of schizophrenia. This suggests other pathological processes must be implicated. This paper aims to elaborate on such theories.

METHODS

Data for this review were sourced from the electronic database PUBMED, and was not limited by language or date of publication.

RESULTS

It has been suggested that multiple 'hits' may be required to unveil the clinical syndrome in susceptible individuals. Such hits potentially first occur in utero, leading to neuronal disruption, epigenetic changes and the establishment of an abnormal inflammatory response. The development of schizophrenia may therefore potentially be viewed as a neuroprogressive response to these early stressors, driven on by changes in tryptophan catabolite (TRYCAT) metabolism, reactive oxygen species handling and N-methyl d-aspartate (NMDA) circuitry. Given the potential for such progression over time, it is prudent to explore the new treatment strategies which may be implemented before such changes become established.

CONCLUSIONS

Outside of the dopaminergic model, the potential pathogenesis of schizophrenia has yet to be fully elucidated, but common themes include neuropil shrinkage, the development of abnormal neuronal circuitry, and a chronic inflammatory state which further disrupts neuronal function. Whilst some early non-dopaminergic treatments show promise, none have yet to be fully studied in appropriately structured randomized controlled trials and they remain little more than potential attractive targets.

Decreased plasma tryptophan and tryptophan/large neutral amino acid ratio in patients with neuroleptic-resistant schizophrenia: relationship to plasma cortisol concentration

Tryptophan is the precursor of kynurenine and kynurenic acid, an α-7 nicotinic acetylcholine receptor antagonist and a N-methyl-D-aspartate (NMDA) receptor antagonist, both of which have been implicated in schizophrenia (SCH), as well as of serotonin. Glucocorticoids can activate the tryptophan-kynurenine pathway and lower plasma tryptophan concentrations. Some previous studies have reported decreases in the plasma tryptophan concentration and the tryptophan/large neutral amino acid (LNAA) ratio, a measure reflecting the brain tryptophan concentration, in patients with SCH. However, the influence of plasma cortisol, which has been reported to be increased in patients with SCH, on plasma tryptophan levels has not been examined in prior studies. Thus, we examined plasma tryptophan concentrations, tryptophan/LNAA ratios, and their relationships with plasma cortisol concentrations in treatment-resistant SCH (TR-SCH) patients, in non-treatment-resistant SCH (NTR-SCH) patients, and in normal controls (NC). Plasma tryptophan concentrations were significantly lower in TR-SCH patients (n=74) than in NTR-SCH patients (n=85) and NC subjects (n=55). In addition, tryptophan/LNAA ratios were significantly lower in TR-SCH patients than in NC subjects. No difference was observed in either measure between NTR-SCH patients and NC subjects. Tryptophan/LNAA ratios and plasma tryptophan concentrations showed a significant negative correlation and a trend-level correlation, respectively, with plasma cortisol concentrations in TR-SCH patients, but not in NTR-SCH patients or in NC subjects. These results suggest the tryptophan-kynurenine pathway may be particularly relevant to TR-SCH and that this may be influenced by the activity of the hypothalamic-pituitary-adrenal axis.

Serotonin-1A receptor gene polymorphism and the ability of antipsychotic drugs to improve attention in schizophrenia

INTRODUCTION

The purpose of this study was to determine if the functional single nucleotide polymorphisms of rs6259 C(-1019)G in the promoter region, which regulates serotonin 5-HT(1A) receptor transcription, affects the ability of antipsychotic drugs to improve attention in patients with schizophrenia.

METHODS

Subjects were neuroleptic-free and meeting DSM-IV-TR criteria for schizophrenia. Psychopathology and attention were evaluated with the Scale for the Assessment of Positive Symptoms (SAPS) and the Scale for the Assessment of Negative Symptoms (SANS) at baseline and 3 months after treatment with atypical antipsychotic drugs (AAPDs). DNA was extracted from peripheral blood following standard procedures. Genotyping was performed with HS-Taq assay (LaboPass).

RESULTS

Data were available from 30 subjects (male/female=19/11), in which 17 had the CC genotype, three had the GG genotype, and 10 were heterozygous. The 3-month treatment with AAPDs was associated with significant improvements in positive and negative symptoms, but not attention as measured by SANS-Attention subscale in the entire subject group. There were no significant differences in the degree of improvements of SAPS and SANS scores between the CC genotype group and the (C/G plus G/G) combined group. On the other hand, improvement of attention was significantly greater for the former group compared to the latter group (P<0.016), suggesting a detrimental influence of the G-allele.

CONCLUSION

These results provide additional support to the role of 5-HT(1A) receptors in some of the cognitive disturbances of schizophrenia. Further studies with a larger number of subjects are warranted.

5-HT1A gene variants and psychiatric disorders: a review of current literature and selection of SNPs for future studies

5-HT1A receptors are key components of the serotonin system, acting both pre- and post- synaptically in different brain areas. There is a growing amount of evidence showing the importance of 5-HT1A in different psychiatric disorders, from mood to anxiety disorders, moving through suicidal behaviour and psychotic disorders. Findings in the literature are not consistent with any definite 5-HT1A influence in psychiatric disorders. 5-HT1A gene variants have been reported to play some role in mood disorders, anxiety disorders and psychotic disorders. Again, the literature findings are not unequivocal. Concerning response to treatment, the C(-1019)G variant seems to be of primary interest in antidepressant response: C allele carriers generally show a better response to treatment, especially in Caucasian samples. Together with the C(-1019)G (rs6295) variant, the Ile28Val (rs1799921), Arg219Leu (rs1800044) and Gly22Ser (rs1799920) variants have been investigated in possible associations with psychiatric disorders, also with no definitive results. This lack of consistency can be also due to an incomplete gene investigation. To make progress on this point, a list of validated single nucleotide polymorphisms (SNPs) covering the whole gene is proposed for further investigations.

Reversal of haloperidol-induced tardive vacuous chewing movements and supersensitive somatodendritic serotonergic response by buspirone in rats

Tardive dyskinesia (TD), a syndrome of involuntary hyperkinesias in the orofacial region that develops in patients chronically treated with neuroleptic agents is a major limitation of the therapy. Rats chronically treated with haloperidol exhibit vacuous chewing movements (VCMs) with the twitching of facial musculature and tongue protrusion. The syndrome is widely used as an animal model of TD. Evidence suggests a role of 5-hydroxytryptamine (5-HT; serotonin)-1A receptors in the pathogenesis and treatment of TD because repeated administration of haloperidol resulted in an increase in the effectiveness of 5-HT-1A receptors while drugs with agonist activity at 5-HT-1A receptors could attenuate haloperidol-induced VCMs. The present study was designed to test the hypothesis that a decrease in the responsiveness of somatodendritic 5-HT-1A receptors by the coadministration of buspirone could reverse the induction of VCMs and supersensitivity at 5-HT-1A receptors by haloperidol. Rats treated with haloperidol at a dose of 1 mg/kg twice a day for 2 weeks displayed VCMs with twitching of facial musculature that increased in a time dependent manner as the treatment continued to 5 weeks. Coadministration of buspirone attenuated haloperidol-induced VCMs after 2 weeks and completely prevented it after 5 weeks. The intensity of 8-hydroxy-2-di (n-propylamino) tetralin (8-OH-DPAT)-induced locomotion was greater in saline+haloperidol injected animals but not in buspirone+haloperidol injected animals. 8-OH-DPAT-induced decreases of 5-HT metabolism were greater in saline+haloperidol injected animals but not in buspirone+haloperidol injected animals. It is suggested that an impaired somatodendritic 5-HT-1A receptor dependent response is a major contributing factor in the pathophysiology of TD and a normalization of the somatodendritic response by drugs may help extending therapeutics in schizophrenia.

Reversal of haloperidol-induced extrapyramidal symptoms by buspirone: a time-related study

Effects of coadministration of buspirone were investigated on the time course of haloperidol-induced extrapyramidal symptoms in rats. Rats treated with haloperidol at a dose of 1 mg/kg exhibited impaired motor coordination and a decrease in exploratory activity. Coadministration of buspirone at a dose of 1 mg/kg attenuated haloperidol-induced deficits of motor coordination but no effect was produced on the deficits of exploratory activity, possibly because of a 'floor effect'. Long-term administration of haloperidol (1 mg/kg) twice a day for 5 weeks did not produce tolerance to haloperidol-induced deficits of exploratory activity. The deficits of motor coordination were attenuated after 4-5 weeks of drug administration. Coadministration of buspirone for 3-5 weeks attenuated and reversed haloperidol-induced deficits of exploratory activity. Deficits of motor coordination were smaller in rats cotreated with buspirone after 1 week but not after 2-5 weeks. Administration of haloperidol for 2 weeks elicited vacuous chewing movements with twitching of facial musculature that increased in a time-dependent manner as the treatment continued to 5 weeks. Animals cotreated with buspirone exhibited a gradual reversal of the response during 2-5 weeks of treatment. The mechanism involved in the attenuation/reversal of haloperidol-induced extrapyramidal symptoms by buspirone is discussed. Prior administration of buspirone for 2 weeks may be of help in the improvement of extrapyramidal symptoms induced by antipsychotic drugs.

Somatodendritic and postsynaptic serotonin-1A receptors in the attenuation of haloperidol-induced catalepsy

The mechanism by which stimulation of somatodendritic and/or postsynaptic 5-hydroxytryptamine (5-HT, serotonin)-1A receptor could attenuate acute Parkinsonian-like effects of typical antipsychotics is investigated by comparing the anticataleptic and neurochemical effects of 8-hydroxy-2-di-n-propylaminotetralin (8-OH-DPAT) and buspirone in rats injected with haloperidol. Cataleptic effects of a submaximal dose (1 mg/kg) of haloperidol were attenuated more by prior administration of 8-OH-DPAT (0.25 mg/kg) than buspirone (1 mg/kg). Striatal 5-HT metabolism decreased more in buspirone- than 8-OH-DPAT-injected animals. Administration of haloperidol did not alter 5-HT metabolism in saline-, 8-OH-DPAT- or buspirone-injected animals. Dopamine decreased and its metabolite homovanillic acid (HVA) increased in the striatum of rats injected with buspirone. Effects of 8-OH-DPAT on dopamine metabolism were not significant. Haloperidol-induced increases of dopamine metabolites were attenuated by prior administration of 8-OH-DPAT, but not buspirone. The mechanism by which stimulation of somatodendritic as well as postsynaptic 5-HT-1A receptors could attenuate haloperidol-induced catalepsy is discussed. The findings have potential implications in the treatment of schizophrenia and motor behavior.

Platelet serotonin and plasma prolactin and cortisol in healthy, depressed and schizophrenic women

Serotonin (5-hydroxytryptamine, 5-HT) is involved in the regulation of hypothalamic-pituitary-adrenal axis (HPA) activity and prolactin (PRL) secretion. The present study examined the relationship between platelet 5-HT and plasma cortisol and PRL concentrations in 20 schizophrenic, 25 depressed, and 25 healthy women. At the time of blood sampling, the schizophrenic and depressed patients had been drug-free for at least 7 days. Platelet 5-HT, plasma cortisol and PRL concentrations were determined by spectrofluorimetric, radioimmunoassay and immunoradiometric methods, respectively. Platelet 5-HT concentration was significantly higher in schizophrenic patients than in depressed patients or in healthy controls, while it was significantly lower in depressed patients than in healthy controls or in schizophrenic patients. Plasma cortisol levels were significantly increased both in schizophrenic and in depressed patients compared with values in healthy controls. Values of plasma PRL were similar across groups. A significant correlation was found between platelet 5-HT and plasma cortisol, and platelet 5-HT and plasma PRL concentrations in healthy controls, but not in schizophrenic or depressed patients. There was no significant relationship between plasma PRL and cortisol levels in any of the groups. Our data, although obtained on peripheral biochemical markers, indicate that depression and schizophrenia are characterized by disturbed 5-HT transmission and dysregulated HPA axis activity.

Decreased 5-HT1A receptor binding in amygdala of schizophrenia

BACKGROUND

On the basis of postmortem data and the pharmacological action of atypical antipsychotics, serotonin-1A receptors are of interest in the study of the pathophysiology of schizophrenia. To investigate serotonin-1A receptors in schizophrenia and their relation to symptoms, we measured the availability of serotonin-1A receptors in patients with schizophrenia using positron emission tomography with [carbonyl-(11)C]WAY-100635.

METHODS

Serotonin-1A receptor binding of 11 patients with schizophrenia (8 drug-naive and 3 drug-free) was compared with that of 22 age-matched and gender-matched healthy control subjects. Symptoms were assessed using the Positive and Negative Syndrome Scale. Serotonin-1A receptor binding in selected regions of interest was quantified by binding potential obtained by the reference tissue method.

RESULTS

The regional binding potential value was lower in the amygdala by about 19% in patients with schizophrenia than in normal controls. A significant negative correlation was observed between binding potential in the amygdala and the negative and depression/anxiety symptom scores on the five-symptom subscale of the Positive and Negative Syndrome Scale.

CONCLUSIONS

Decreased serotonin-1A receptor binding in the amygdala may underlie the affective components included in the symptoms of negative and depression/anxiety in schizophrenia.

Effects of acute tryptophan depletion on executive function in healthy male volunteers

BACKGROUND

Neurocognitive impairment is frequently described in a number of psychiatric disorders and may be a direct consequence of serotonergic dysfunction. As impairments in executive functions are some of the most frequently described, the purpose of this study was to examine the performance of normal volunteers on a range of executive tasks following a transient reduction of central serotonin (5-HT) levels using the method of acute tryptophan depletion (ATD).

METHODS

Fifteen healthy male subjects participated in a within-subject, double-blind, counterbalanced crossover study. ATD was induced by ingestion of a 100 g amino-acid drink. Executive function was evaluated using the Wisconsin Card Sorting Test, Stroop, Verbal Fluency and Trail Making. Visual analogue scales were administered to assess mood.

RESULTS

Plasma free and total tryptophan concentrations were significantly reduced by the depleting drink (P < 0.001). ATD selectively improved motor speed/ attention on the Trails A test (P = 0.027), with no effect on subjective ratings of mood. Interaction effects between drink and the order of drink administration were observed on most neurocognitive tests.

CONCLUSIONS

The improvement in simple motor speed/ attention following ATD is in keeping with the ascribed role of 5-HT in the cortex, however performance on tests of executive function is not robustly altered. The presence of interaction effects on most tasks suggests that subtle changes may occur but are masked, possibly by simple learning effects, in the context of a crossover design. This has implications for the design of future studies, particularly those examining executive functions.

Enhancement of serotonin-1A receptor dependent responses following withdrawal of haloperidol in rats

Although haloperidol is widely prescribed for the treatment of schizophrenia, its beneficial effects are accompanied by extrapyramidal side effects (EPS). In view of a role of 5-hydroxytryptamine (5-HT; serotonin)-1A receptors in the elicitation of EPS, the present study concerns pre- and postsynaptic responses to a selective 5-HT-1A receptor agonist, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) following acute and chronic administration of haloperidol in rats. In the acute administration study, effects of 8-OH-DPAT (0.5 mg/kg) were monitored 30 min after single injection of haloperidol (5 mg/kg). In the chronic administration study, effects of 8-OH-DPAT (0.5 mg/kg) were monitored 48 h after withdrawal from repeated (two times a day for 2 weeks) administration of haloperidol (5 mg/kg). The intensity of 5-HT syndrome elicited by 8-OH-DPAT was taken as measure of postsynaptic response. 8-OH-DPAT-induced decreases of 5-HT synthesis were taken as measure of presynaptic response. Results showed that 8-OH-DPAT-induced locomotion was smaller in acute haloperidol-treated rats. Conversely, these effects of 8-OH-DPAT were greater in chronic haloperidol-treated rats. Animals injected acutely or chronically with haloperidol exhibited greater 5-HT synthesis in the striatum. Administration of 8-OH-DPAT did not decrease 5-HT synthesis in the striatum of acute haloperidol-treated rats but decreased it in the striatum of chronic haloperidol-treated rats. The results show an increase in the effectiveness of pre- and postsynaptic 5-HT-1A receptor dependent responses following chronic administration of haloperidol. A causal role of 5-HT-1A receptor responsiveness in the greater incidences of EPS in patients treated with typical neuroleptics such as haloperidol is discussed.