CSF GABA is reduced in first-episode psychosis and associates to symptom severity.

Schizophrenia is characterized by a multiplicity of symptoms arising from almost all domains of mental function. γ-Aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the brain and is increasingly recognized to have a significant role in the pathophysiology of the disorder. In the present study, cerebrospinal fluid (CSF) concentrations of GABA were analyzed in 41 first-episode psychosis (FEP) patients and 21 age- and sex-matched healthy volunteers by high-performance liquid chromatography. We found lower CSF GABA concentration in FEP patients compared with that in the healthy volunteers, a condition that was unrelated to antipsychotic and/or anxiolytic medication. Moreover, lower CSF GABA levels were associated with total and general score of Positive and Negative Syndrome Scale, illness severity and probably with a poor performance in a test of attention. This study offers clinical in vivo evidence for a potential role of GABA in early-stage schizophrenia.

Increased number of monocytes and plasma levels of MCP-1 and YKL-40 in first-episode psychosis.

OBJECTIVE: Accumulating evidence implicates immune activation in the development of schizophrenia. Here, monocyte numbers, monocyte chemoattractant protein-1 (MCP-1) and chitinase-3-like protein 1 (YKL-40) were investigated in plasma and cerebrospinal fluid (CSF) in first-episode psychosis (FEP) patients. METHOD: CSF and blood were sampled from 42 first-episode psychosis (FEP) patients and 22 healthy controls. The levels of YKL-40 and MCP-1 were measured using electrochemiluminescence assay, and blood monocytes were counted using an XN-9000-hematology analyzer. RESULTS: We found higher plasma levels of MCP-1 and YKL-40 in FEP patients compared with healthy controls, a condition that was unrelated to antipsychotic and/or anxiolytic medication. This was combined with an increased number of blood monocytes and a borderline significant increase in YKL-40 levels in the CSF of tobacco-free FEP patients. Plasma or CSF chemokines or blood monocytes did not correlate with the severity of symptoms or the level of functioning. CONCLUSION: These data demonstrate activation of monocytes in FEP and strengthens the idea of an immune dysfunction of psychotic disorders. Further studies are required to perceive a role of YKL-40 and MCP-1 in the initiation and progression of schizophrenia.

A genome-wide association study of kynurenic acid in cerebrospinal fluid: implications for psychosis and cognitive impairment in bipolar disorder.

Elevated cerebrospinal fluid (CSF) levels of the glia-derived N-methyl-D-aspartic acid receptor antagonist kynurenic acid (KYNA) have consistently been implicated in schizophrenia and bipolar disorder. Here, we conducted a genome-wide association study based on CSF KYNA in bipolar disorder and found support for an association with a common variant within 1p21.3. After replication in an independent cohort, we linked this genetic variant-associated with reduced SNX7 expression-to positive psychotic symptoms and executive function deficits in bipolar disorder. A series of post-mortem brain tissue and in vitro experiments suggested SNX7 downregulation to result in a caspase-8-driven activation of interleukin-1ß and a subsequent induction of the brain kynurenine pathway. The current study demonstrates the potential of using biomarkers in genetic studies of psychiatric disorders, and may help to identify novel drug targets in bipolar disorder.

Repeated LPS Injection Induces Distinct Changes in the Kynurenine Pathway in Mice.

The immune system has been recognized as a potential contributor to psychiatric disorders. In animals, lipopolysaccharide (LPS) is used to induce inflammation and behaviors analogous to some of the symptoms in these disorders. Recent data indicate that the kynurenine pathway contributes to LPS-induced aberrant behaviors. However, data are inconclusive regarding optimal LPS dose and treatment strategy. Here, we therefore aimed to evaluate the effects of single versus repeated administration of LPS on the kynurenine pathway. Adult C57BL6 mice were given 0.83 mg/kg LPS as a single or a repeated injection (LPS + LPS) and sacrificed after 24, 48, 72, or 120 h. Mice receiving LPS + LPS had significantly elevated brain kynurenine levels at 24 and 48 h, and elevated serum kynurenine at 24, 48 and 72 h. Brain kynurenic acid and quinolinic acid were significantly increased at 24 and 48 h in mice receiving LPS + LPS, whereas serum kynurenic acid levels were significantly decreased at 24 h. The increase of brain kynurenic acid by LPS + LPS was likely unrelated to the higher total dose as a separate group of mice receiving 1.66 mg/kg LPS as single injection 24 h prior to sacrifice did not show increased brain kynurenic acid. Serum quinolinic acid levels were not affected by LPS + LPS compared to vehicle. Animals given repeated injections of LPS showed a more robust induction of the kynurenine pathway in contrast to animals receiving a single injection. These results may be valuable in light of data showing the importance of the kynurenine pathway in psychiatric disorders.

The KMO allele encoding Arg452 is associated with psychotic features in bipolar disorder type 1, and with increased CSF KYNA level and reduced KMO expression.

The kynurenine pathway metabolite kynurenic acid (KYNA), modulating glutamatergic and cholinergic neurotransmission, is increased in cerebrospinal fluid (CSF) of patients with schizophrenia or bipolar disorder type 1 with psychotic features. KYNA production is critically dependent on kynurenine 3-monooxygenase (KMO). KMO mRNA levels and activity in prefrontal cortex (PFC) are reduced in schizophrenia. We hypothesized that KMO expression in PFC would be reduced in bipolar disorder with psychotic features and that a functional genetic variant of KMO would associate with this disease, CSF KYNA level and KMO expression. KMO mRNA levels were reduced in PFC of bipolar disorder patients with lifetime psychotic features (P=0.005, n=19) or schizophrenia (P=0.02, n=36) compared with nonpsychotic patients and controls. KMO genetic association to psychotic features in bipolar disorder type 1 was studied in 493 patients and 1044 controls from Sweden. The KMO Arg(452) allele was associated with psychotic features during manic episodes (P=0.003). KMO Arg(452) was studied for association to CSF KYNA levels in an independent sample of 55 Swedish patients, and to KMO expression in 717 lymphoblastoid cell lines and 138 hippocampal biopsies. KMO Arg(452) associated with increased levels of CSF KYNA (P=0.03) and reduced lymphoblastoid and hippocampal KMO expression (P≤0.05). Thus, findings from five independent cohorts suggest that genetic variation in KMO influences the risk for psychotic features in mania of bipolar disorder patients. This provides a possible mechanism for the previous findings of elevated CSF KYNA levels in those bipolar patients with lifetime psychotic features and positive association between KYNA levels and number of manic episodes.

LPS-induced cortical kynurenic acid and neurogranin-NFAT signaling is associated with deficits in stimulus processing during Pavlovian conditioning.

The N-Methyl-d-Aspartate receptor (NMDAR) antagonist kynurenic acid (KYNA) and the post-synaptic calmodulin binding protein neurogranin (Nrgn) have been implicated in neurological and neuropsychiatric conditions including Alzheimer's disease and schizophrenia. This study indicates that systemic dual-lipopolysaccharide (LPS) injections increases KYNA in the medial prefrontal cortex (mPFC), which is accompanied with increased phosphorylation of nuclear factor kappa chain of activated B cells (NFκB) and activation of the nuclear factor of activated T- cells (NFAT). Our results also indicate that dual-LPS increases Nrgn phosphorylation and concomitantly reduces phosphorylation of calmodulin kinase-II (CaMKII). We confirmed that systemic blockade of kynurenine-3 monooxygenase in conjunction with kynurenine administration results in significant increases in Nrgn phosphorylation and a significant reduction of CaMKII phosphorylation in the mPFC. Consequently, dual-LPS administration induced significant impairments in stimulus processing during Pavlovian conditioning. Taken together, our study indicates that elevations in KYNA in the mPFC can directly regulate NMDA-Nrgn-CaMKII signaling, suggesting that neuroinflammatory conditions affecting this pathway may be associated with cognitive dysfunction.

Maternal and fetal risk factors for bladder exstrophy: A nationwide Swedish case-control study.

INTRODUCTION: Bladder exstrophy is a rare, congenital, complex malformation where the underlying cause is largely unknown. Both environmental and genetic mechanisms are thought to be involved. There are divergent results concerning the prevalence, birth descriptive data, and potential maternal risk factors for bladder exstrophy. Few previous studies have reflected nationwide populations, population registers, or spanned a longer period of time. OBJECTIVE: To describe and assess bladder exstrophy and the potential maternal risk factors, for a time period of four decades, by conducting a nationwide register study of bladder exstrophy in Sweden. METHODS: A matched-design, case-control, linkage-analysis study nested within the entire pool of live births in Sweden between 1973 and 2011 was performed. Cases with bladder exstrophy were identified using nationwide population-based birth and health registers. Inclusion criteria were people born in Sweden with the classification of bladder exstrophy according to the ICD coding system. Cases were matched with five controls per patient, based on birth year and sex. Prevalence was assessed and birth descriptive data were compiled. Potential maternal risk factors were obtained from medical birth registers of cases and assessed using conditional and multivariate logistic regression models to obtain odds ratios as a measure of the relative risk. Classification of the diagnosis in the registers constituted a possible limitation for determining the correct study population, which demanded strict validation and inclusion criteria. All data were collected prospectively, thereby avoiding potential recall bias. RESULTS: The prevalence was calculated to be approximately 3 per 100,000 live births, with a male-to-female ratio of 1.14:1. In 92.5% of the cases, bladder exstrophy was an isolated malformation without associated major malformations. However, 41% had had surgery for congenital inguinal hernia and 11% of the male subjects had been operated on for cryptorchidism. A significantly higher proportion of cases had a birth weight <1500 g compared with controls, but other characteristics were comparable with controls. High maternal age was the only significant potential associated maternal risk factor. CONCLUSIONS: One hundred and twenty children born with bladder exstrophy in Sweden during the last four decades were identified; this resulted in prevalence in Sweden of 3 per 100,000. The prevalence was stable over time and the sex ratio was equal. Birth characteristics were comparable to controls, and bladder exstrophy generally occurred as an isolated malformation without major associated malformations. Advanced maternal age was the only significant potential maternal risk factor.

Elevated levels of kynurenic acid in the cerebrospinal fluid of male patients with schizophrenia.

Previous studies have shown that endogenous brain levels of kynurenic acid (KYNA), a glutamate receptor antagonist, are elevated in patients with schizophrenia. Here we analyse KYNA in the cerebrospinal fluid (CSF) from a large cohort, including male healthy controls (n=49) and male patients with schizophrenia (n=90). We found that male patients with schizophrenia had significantly higher levels of CSF KYNA compared to healthy male controls (1.45 nM+/-0.10 vs. 1.06 nM+/-0.06 in the control group). Furthermore, when the patients with schizophrenia were divided into subgroups we found that CSF KYNA levels were significantly elevated in drug-naïve, first episode patients (1.53 nM+/-0.19, n=37) and in patients undergoing treatment with antipsychotic drugs (1.53 nM+/-0.17, n=34) compared to healthy male controls. No elevated CSF KYNA levels were detected in drug-free patients with schizophrenia, i.e. patients previously undergoing antipsychotic medications but drug-free at time of sampling (1.16 nM+/-0.10, n=19). Present results confirm that CSF KYNA concentration is elevated in patients with schizophrenia and are consistent with the hypothesis that KYNA contributes to the pathophysiology of the disease.

Effects of mCPP on the extracellular concentrations of serotonin and dopamine in rat brain.

Intravenous administration of m-chloro-phenylpiperazine (mCPP) (0.25 or 2.5 mg/kg) induced a marked and dose-related increase in extracellular concentrations of serotonin in hippocampus (300-1,400% of baseline) as measured using in vivo microdialysis in awake male Wistar rats of the spontaneously hypertensive (SH) strain. Indicating that the effect of mCPP was caused by a reversal of the serotonin transporter, it was antagonized by pretreatment with the serotonin re-uptake inhibitor citalopram (10 mg/kg) but was unaffected by local administration of the sodium channel blocker tetrodotoxin (TTX; 1 microns). mCPP was also shown to induce an increase in extracellular concentrations of dopamine in the nucleus accumbens and the striatum of SH rats and in the nucleus accumbens of rats of the Sprague-Dawley (SD) strain; this effect of mCPP was, however, much weaker (125-170% of baseline) than the effect on serotonin; moreover, it seems to be TTX-sensitive. In anesthetized SD rats, mCPP induced a moderate reduction of nigral dopamine cell firing rate; supporting the assumption that this effect is secondary to the observed increase in dopamine release, it was blocked by pretreatment either with the dopamine synthesis inhibitor alpha-methyl-para-tyrosine or with the dopamine D2 receptor antagonist haloperidol. In conclusion, the results suggest that mCPP induces a marked, TTX-insensitive increase in serotonin release in rat brain, but only a modest and TTX-sensitive increase in the extracellular levels of dopamine.

Role of primary sensory neurons in the central effects of nicotine.

Utilizing single unit recording techniques the nicotine-induced excitation of noradrenaline (NA)-containing neurons in the locus coeruleus (LC) was analyzed. Low doses of nicotine (40-160 micrograms, IV) were found to dose-dependently increase the LC firing rate. The effect was antagonized by pretreatment with the quaternary ganglionic blockers hexamethonium (12 mg/kg, IP) and chlorisondamine (0.3 mg/kg, IV). Also, neonatal treatment with capsaicin, a procedure that is associated with a selective degeneration of primary sensory C-fibre afferents, clearly antagonized the effect of nicotine on LC neurons. The typical effect of nicotine on LC discharge was, in all essentials, mimicked by the quaternary nicotinic agonist tetramethylammonium (TMA). We here propose that the action of nicotine on central NA neurons is primarily executed peripherally via activation of primary sensory C-fibre afferents.

Emotional hyperthermia in spontaneously hypertensive rats.

Basal body temperature of spontaneously hypertensive rats (SHR) was found to be significantly elevated compared to normotensive Wistar Kyoto rats (WKR). The hypothermic response to low doses of the alpha 2-receptor agonist clonidine was significantly smaller in SHR compared to WKR. In contrast, the thermoregulatory response of SHR to a non-noxious stressor was heightened. We propose that the elevated basal temperature observed in SHR is not due to an impaired thermolysis but the result of a noradrenaline-mediated hyperreactivity to environmental stress, e.g. handling of the animals during the temperature measurement procedure.

A role of excitatory amino acids in the activation of locus coeruleus neurons following cutaneous thermal stimuli.

Previous electrophysiological experiments have shown that brain noradrenaline neurons in the locus ceruleus are activated by thermal cutaneous stimuli. In the present study a putative involvement of excitatory amino acids (EAA) in cutaneous LC activation was analyzed. Intraventricular administration of kynurenic acid (1 mumol), a broad spectrum EAA antagonist, or the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 0.1 mumol) as well as subcutaneous administration of the specific NMDA antagonist MK 801 (2 mg/kg) almost totally abolished the response of LC neurons to both non-noxious and noxious cutaneous sensory stimuli. We propose that the activation of LC neurons following thermal cutaneous stimuli is mediated via release of EAA from nerve terminals emanating from nucleus paragigantocellularis (PGi).

Effect of adrenaline synthesis inhibition on brain noradrenaline neurons in locus coeruleus.

The functional significance of the morphologically identified adrenaline (A)-mediated input to the noradrenergic nucleus locus coeruleus (LC) was pharmacologically analyzed. By means of single unit recording techniques the LC neurons in the rat brain were studied following administration of SK&F 64139 and DCMB, drugs which are both potent inhibitors of the A-forming enzyme phenylethanolamine-N-methyltransferase (PNMT). SK&F 64139 (1-200 mg/kg i.v.) caused an immediate, dose-dependent and long-lasting increase in firing rate of the LC neurons. The dose-response curve for the LC inhibitory effect of the alpha 2-receptor agonist clonidine was shifted in parallel to the right by pretreatment with SK&F 64139. All the above mentioned effects of SK&F 64139 were mimicked by SK&F 72223, a structurally analogous compound which is reported to lack PNMT inhibitory activity. Consequently, the activation of LC neurons by SK&F 64139 is probably not related to its capacity to inhibit the synthesis of A but rather to some other action of the drug, such as an alpha 2-receptor blocking effect. In contrast to SK&F 64139, the other PNMT inhibitor tested, DCMB (1-60 mg/kg), produced no significant activation of the LC neurons and but little clonidine antagonistic action. Thus, judging from these experiments, DCMB is devoid of significant alpha 2-receptor blocking properties. At the time for maximal brain A depletion after DCMB administration (4-6 h) the average firing rate of randomly encountered LC neurons was unaltered when compared with controls. In contrast, pretreatment with the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine methylester, which causes depletion also of brain noradrenaline, significantly increased LC neuronal firing rates. These data indicate that if there exists a physiologically relevant A-mediated input to the LC, this is not of critical importance for the tonic activity of the LC neurons.

Antagonistic effects of somatostatin and substance P on respiratory regulation in the rat ventrolateral medulla oblongata.

Substance P (SP) in the dose range 0.75-1.5 nmol exerts a potent stimulatory effect on ventilation after microinjection into the rat ventrolateral medulla oblongata (VLM; n. reticularis lateralis, n. paragigantocellularis lateralis). A significant but less pronounced effect is also seen in the dorsal medulla (DM; n. tractus solitarius). Somatostatin (0.6-1.8 nmol) inhibited ventilation and induced apnoea after microinjection into the VLM but not the DM. Serial microinjections of the two peptides showed a reciprocal antagonistic action in the VLM but not in the DM. The apnoea-inducing effect of SOM was blunted by SP while SOM reduced the ventilatory stimulation induced by SP. Extracellular single unit recordings were performed following the microiontophoretic application of SP and/or SOM to respiratory-related and non-respiratory-related neurons in the VLM and DM. Although a heterogeneous population of neurons were recorded from, the majority of respiratory-related units in the VLM responded with excitation to SP and inhibitory to SOM. A direct interaction between the peptides was seen in some respiratory-related units. The neurons not responding to either of the peptides were usually non-respiratory. Dorsal to the VLM, the type of response to the two peptides was less likely to be antagonistic and a wider distribution of response types were recorded. The results indicate a direct physiological antagonism between SP and SOM regarding their effects on respiratory regulation elicited in the VLM.

Sigma-receptors: implication for the control of neuronal activity of nigral dopamine-containing neurons.

Using extracellular single unit recording techniques, we analyzed the significance of sigma-receptors in the neuronal control of dopamine (DA) neurons in the zona compacta of the substantia nigra. Administration of racemic trans-9-methoxy-4-benzyl-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinoline (HW 173), a drug displaying high and specific affinity for sigma-receptors, was not associated with any change in the firing rate of DA neurons. Furthermore, pretreatment with the drug did not affect the dose-response curve for the inhibitory effects of the DA receptor agonist apomorphine or the mixed DA agonist/sigma-receptor ligand (+)-3-(3-hydroxyphenyl)-N-1-propyl)piperidine ((+)-3-PPP). In contrast to the effects of HW 173 on the DA cell firing rate, the firing pattern of the DA cells was significantly changed by the drug. The data suggest that sigma-receptors do not play a pivotal role in the control of the firing rate of DA neurons in the substantia nigra. Rather, they may have a function in the regulation of the firing pattern of these neurons.

The rat nucleus paragigantocellularis as a relay station to mediate peripherally induced central effects of nicotine.

Previous electrophysiological studies have shown that intravenously administered nicotine in low doses indirectly excites noradrenergic locus coeruleus (LC) neurons. In the present study this effect of nicotine was attenuated (to about 25% of control response) by injection of lidocaine into the nucleus paragigantocellularis (PGi) whereas injection into the nucleus prepositus hypoglossi (PrH) had no effect in this regard. Whereas the basal firing rate of LC neurons was not affected by lidocaine injection into the PGi, more than 50% of the LC neurons displayed increased firing rate following lidocaine injection into the PrH. It is suggested that the peripherally induced effect of nicotine on LC neurons is indirectly mediated via activation of the PGi.

Reduced responsiveness of locus coeruleus neurons to cutaneous thermal stimuli in capsaicin-treated rats.

Recent electrophysiological experiments have shown that brain norepinephrine (NE) neurons in the locus coeruleus (LC) are activated by cutaneous thermal stimuli of both non-noxious and noxious character. In the present study the LC neuronal response to thermal stimuli was used to evaluate cutaneous thermal sensitivity in capsaicin-treated rats, a treatment that is described to cause impaired thermoregulation. Capsaicin treatment, of neonates as well as of adult rats, caused a reduced responsiveness of brain LC neurons to thermal stimuli. The results suggest that a reduction in peripheral thermal afferent transmission may be one mechanism underlying the capsaicin-induced thermoregulatory dysfunction.

Oxytocin increases locus coeruleus alpha 2-adrenoreceptor responsiveness in rats.

Oxytocin induces several antistress-like effects in rats. As the central noradrenergic nucleus locus coeruleus (LC) participates in arousal reactions and cardiovascular control, we used extracellular single-cell recording techniques to investigate a potential influence of oxytocin on LC neuronal activity. Oxytocin (1 mg/kg s.c.) given once a day for 5 days to male rats, increased the responsiveness of noradrenergic LC neurons to intravenous (i.v.) administration of clonidine, when compared to controls treated with saline for 5 days (P < 0.01). The spontaneous firing rate was not affected by oxytocin treatment. This study indicates that oxytocin treatment increases the responsiveness of LC alpha 2-adrenoreceptors.

Kynurenic acid levels are elevated in the cerebrospinal fluid of patients with schizophrenia.

Kynurenic acid is an endogenous glutamate antagonist with a preferential action at the glycine-site of the N-methyl D-aspartate-receptor. Mounting evidence indicate that the compound is significantly involved in basal neurophysiological processes in the brain. In the present investigation, cerebrospinal fluid (CSF) level of kynurenic acid was analyzed in 28 male schizophrenic patients and 17 male healthy controls by means of high pressure liquid chromatography and fluorescence detection. Schizophrenic patients showed elevated CSF levels of kynurenic acid (1.67+/-0.27 nM) compared to the control group (0.97+/-0.07 nM). Furthermore, CSF levels of kynurenic acid in schizophrenic patients were also found to correlate with age. The present finding is indicative of a contribution of kynurenic acid in the pathogenesis of schizophrenia.