Cost-effectiveness analysis of a first-trimester screening test for preterm preeclampsia in the Netherlands.

OBJECTIVES: The risk of preterm preeclampsia (PT PE) can significantly be reduced by starting acetylsalicylic acid ≤ 16 weeks of gestational age. First trimester predictive models based on maternal risk factors to effectively start this therapy lacked sufficient power, but recent studies showed that these models can be improved by including test results of biochemical and/or -physical markers. To investigate whether testing a biochemical marker in the first trimester is cost-effective in the Netherlands, a cost-effectiveness analysis was performed in this study. STUDY DESIGN: The outcome of this study was expressed as an incremental cost-effectiveness ratio (ICER) with as effect prevented PT PE cases. To evaluate the impact of each model parameter and to determine model uncertainties, both univariate and probabilistic sensitivity analyses were performed. RESULTS: When compared to the baseline strategy, the test strategy is estimated to save almost 4 million euros per year on a national scale and at the same time this would prevent an additional 228 PT PE cases. The sensitivity analyses showed that the major drivers of the result are the costs to monitor a high-risk pregnancy and the specificity and that most of the model simulations were in the southeast quadrant: cost saving and more prevented complications. CONCLUSIONS: This study showed that a first-trimester test strategy to screen for PT PE in the first trimester is potentially cost-effective in the Dutch healthcare setting. The fact that the specificity is a major driver of the ICER indicates the importance for a (new) screening model to correctly classify low-risk pregnancies.

Early pregnancy biomarker discovery study for spontaneous preterm birth.

(1) OBJECTIVE: discover new candidate biomarkers for spontaneous preterm birth in early pregnancy samples. When fully clinically validated, early pregnancy biomarkers for sPTB give the possibility to intervene or monitor high-risk pregnancies more intensively through, as example, pelvic exams, ultrasound or sonographic cervical length surveillance. (2) STUDY DESIGN: Early pregnancy serum samples of eight spontaneous extreme and very preterm birth cases (<32 weeks of gestational age) without any symptoms of preeclampsia and fetal growth restriction and eight uncomplicated pregnancies were analyzed by liquid chromatography mass spectrometry (LC-MS). Thirteen proteins, which were differentially expressed according to the LC-MS data, were subsequently selected for confirmation by enzyme-linked immunosorbent assay (ELISA). (3) RESULTS: Differential expression of four candidate biomarkers was confirmed by ELISA with decreased early pregnancy levels of gelsolin and fibulin-1 and increased levels of c-reactive protein and complement C5 in the preterm birth group. (4) CONCLUSIONS: The confirmed candidate biomarkers are all to some extent related to inflammatory pathways and/or the complement system. This supports the hypothesis that both play a role in extreme and very preterm birth without any symptoms of preeclampsia and fetal growth restriction. The predictive value of complement C5, c-reactive protein, fibulin-1 and gelsolin should, therefore, be validated in another cohort with early pregnancy samples.

First trimester serum biomarker discovery study for early onset, preterm onset and preeclampsia at term.

INTRODUCTION: Preeclampsia (PE) is a heterogeneous syndrome during pregnancy and postpartum and it is subdivided in this study into early onset (<34 weeks), preterm onset (34-37 weeks) and PE at term (>37 weeks). First trimester models currently lack a sufficient power to predict PE, but inclusion of biochemical markers shows an improvement of their predictive power. The aim of this study was to perform a biomarker discovery study in order to find possible novel first trimester biomarkers for each PE subtype. Further, our findings were related to available literature and the possible role of the proteins in the development of preeclampsia was discussed. METHODS: In this study, 9 early onset (<34 weeks), 8 preterm onset (34-37 weeks), 6 PE at term (>37 weeks) and 23 control samples were drawn between 11 and 14 weeks gestational age. Serum samples were prepared for liquid chromatography mass spectrometry analysis and protein data were exported for statistical analyses. All differentially expressed proteins were further evaluated by searching literature in MEDLINE, Embase and Web of science and differential expression of two proteins, which were not yet associated with PE, was verified through enzyme-linked immunosorbent assay (ELISA). RESULTS: After statistical analysis, six, four and eight proteins were differently expressed in early onset, preterm onset and PE at term, respectively. After exclusion of antibody fragments, only nine proteins remained. Seven out of these nine proteins were already in literature associated with preeclampsia and only three of them were described as differentially expressed in the first trimester or early second trimester of preeclamptic pregnancies. Differential expression of Apolipoprotein D (ApoD), which was not yet associated with PE, was confirmed by ELISA in both early and preterm onset PE in the first trimester. DISCUSSION: In this study, two main observations were made. First, some of the differentially expressed proteins have a role in the same biological pathway, such as the acute phase response or endometrium receptivity, and their differential expression was observed in all three PE subtypes. This observation supports the hypothesis that classification of PE could be more accurate when subtyping is based on the etiology and/or phenotype instead of the arbitrary parameter gestational age at onset or delivery. Second, seven differential expressed proteins were already associated in literature with preeclampsia, but this association was for only three of them observed in the first trimester. In addition, ApoD was not yet associated with PE in other studies and, moreover, its differential expression was confirmed by ELISA. Therefore the predictive power of these proteins in the first trimester is worth evaluating in a larger and more heterogeneous cohort.

Healthy and preeclamptic pregnancies show differences in Guanylate-Binding Protein-1 plasma levels.

The large interferon-inducible anti-angiogenic pro-inflammatory GTPase Guanylate Binding Protein-1 (GBP-1) is produced and secreted by activated endothelial cells and is highly induced by inflammatory cytokines and inhibited by angiogenic growth factors. During pregnancy a generalized mild inflammatory response is observed. During preeclampsia this generalized inflammatory response is even further activated and activation of the endothelium occurs. We hypothesized that GBP-1 is increased in healthy pregnancy and will be even further increased during preeclampsia. In the first experiment, plasma and placentas were collected from healthy and preeclamptic pregnancies. Plasma was also collected from non-pregnant women. For the second experiment longitudinal blood samples from women with a healthy or preeclamptic pregnancy were collected from the end of the first trimester until birth and one sample postpartum. The plasma GBP-1 levels were measured by ELISA and GBP-1 mRNA and protein levels in the placenta were tested by qPCR and immunohistochemistry. During pregnancy higher plasma concentrations of GBP-1 compared with non-pregnant women were observed. Surprisingly, during preeclampsia, plasma GBP-1 levels were lower than in control pregnancies and similar to the level of non-pregnant controls. Placental GBP-1 mRNA levels were not different between healthy and preeclamptic pregnancies and GBP-1 protein was virtually undetectable in the trophoblast by immunohistochemistry in placental tissue. Evaluation of longitudinal samples showed that plasma GBP-1 concentrations increased towards the end of pregnancy in healthy pregnancies, but not in preeclampsia. In line with our hypothesis, we found higher GBP-1 plasma levels during healthy pregnancy. However, plasma GBP-1 did not further increase during preeclampsia, but was stable. Further studies are needed to evaluate why GBP-1 does not increase during preeclampsia.

First trimester secreted Frizzled-Related Protein 4 and other adipokine serum concentrations in women developing gestational diabetes mellitus.

BACKGROUND: The aim of this study was to evaluate whether soluble frizzled-related protein 4 (sFRP4) concentration in the first trimester of pregnancy is individually, or in combination with Leptin, Chemerin and/or Adiponectin, associated with the development of gestational diabetes (GDM). METHODS: In a nested case-control study, 50 women with GDM who spontaneously conceived and delivered a live-born infant were matched with a total of 100 uncomplicated singleton control pregnancies based on body mass index (± 2 kg/m2), gestational age at sampling (exact day) and maternal age (± 2 years). In serum samples, obtained between 70-90 days gestational age, sFRP4, Chemerin, Leptin and Adiponectin concentrations were determined by ELISA. Statistical comparisons were performed using univariate and multi-variate logistic regression analysis after logarithmic transformation of the concentrations. Discrimination of the models was assessed by the area under the curve (AUC). RESULTS: First trimester sFRP4 concentrations were significantly increased in GDM cases (2.04 vs 1.93 ng/ml; p<0.05), just as Chemerin (3.19 vs 3.15 ng/ml; p<0.05) and Leptin (1.44 vs 1.32 ng/ml; p<0.01). Adiponectin concentrations were significantly decreased (2.83 vs 2.94 ng/ml; p<0.01) in GDM cases. Further analysis only showed a weak, though significant, correlation of sFRP4 with Chemerin (R2 = 0.124; p<0.001) and Leptin (R2 = 0.145; p<0.001), and Chemerin with Leptin (R2 = 0.282; p<0.001) in the control group. In a multivariate logistic regression model of these four markers, only Adiponectin showed to be significantly associated with GDM (odds ratio 0.12, 95%CI 0.02-0.68). The AUC of this model was 0.699 (95%CI 0.605-0.793). CONCLUSION: In the first trimester of pregnancy, a multi-marker model with sFRP4, Leptin, Chemerin and Adiponectin is associated with the development of GDM. Therefore, this panel seems to be an interesting candidate to further evaluate for prediction of GDM in a prospective study.

A new microdialysis probe for continuous lactate measurement during fetal monitoring: Proof of concept in an animal model.

INTRODUCTION: Cardiotocography (CTG) is currently the most commonly used method for intrapartum fetal monitoring during labor. However, a high false-positive rate of fetal acidosis indicated by CTG leads to an increase in obstetric interventions. We developed a microdialysis probe that is integrated into a fetal scalp electrode allowing continuous measurement of lactate subcutaneously, thus giving instant information about the oxygenation status of the fetus. Our aim was to establish proof of concept in an animal model using a microdialysis probe to monitor lactate subcutaneously. MATERIAL AND METHODS: We performed an in vivo study in adult male wild-type Wistar rats. We modified electrodes used for CTG monitoring in human fetuses to incorporate a microdialysis membrane. Optimum flow rates for microdialysis were determined in vitro. For the in vivo experiment, a microdialysis probe was inserted into the skin on the back of the animal. De-oxygenation and acidosis were induced by lowering the inspiratory oxygen pressure. Oxygenation and heart rate were monitored. A jugular vein cannula was inserted to draw blood samples for analysis of lactate, pH, pco2 , and saturation. Lactate levels in dialysate were compared with plasma lactate levels. RESULTS: Baseline blood lactate levels were around 1 mmol/L. Upon de-oxygenation, oxygen saturation fell to below 40% for 1 h and blood lactate levels increased 2.5-fold. Correlation of dialysate lactate levels with plasma lactate levels was 0.89 resulting in an R2 of .78 in the corresponding linear regression. CONCLUSIONS: In this animal model, lactate levels in subcutaneous fluid collected by microdialysis closely reflected blood lactate levels upon transient de-oxygenation, indicating that our device is suitable for subcutaneous measurement of lactate. Microdialysis probe technology allows the measurement of multiple compounds in the dialysate, such as glucose, albumin, or inflammatory mediators, so this technique may offer the unique possibility to shed light on fetal physiology during the intrapartum period.

Changes in endothelial cell specific molecule 1 plasma levels during preeclamptic pregnancies compared to healthy pregnancies.

OBJECTIVE: We aimed to assess the levels of endothelial cell specific molecule 1 (ESM-1) during pregnancy and preeclampsia. METHODS: Plasma and placental samples were collected from women with a control pregnancy, early- or late-onset preeclamptic women and non-pregnant women (experiment 1). Plasma samples were collected between weeks 12 and birth from pregnant women at high risk for developing preeclampsia (experiment 2). ESM-1 plasma levels were measured by ELISA and in the placenta mRNA and protein were detected by immunohistochemistry and qPCR. RESULTS: In the first experiment we observed lower concentrations of ESM-1 in pregnant women as compared to non-pregnant women and higher concentrations during early- and late-onset preeclampsia as compared to control pregnancies of the same gestational age. Early- and late-onset preeclamptic pregnancies were not different from their subsequent controls in ESM-1 mRNA or protein levels in placental tissue. The second experiment showed that in women who had an control pregnancy, plasma ESM-1 levels were decreased as compared to non-pregnant women, from week 16 ±â€¯2 until the end of pregnancy and returned to non-pregnant levels postpartum. In women who developed early- or late-onset preeclampsia, plasma ESM-1 was also decreased as compared to non-pregnant women from week 20 ±â€¯2 until week 28 ±â€¯2 of pregnancy. Then ESM-1 levels increased and were no longer different from levels in non-pregnant women on weeks 32 and 36. CONCLUSIONS: Plasma ESM-1 levels are decreased during pregnancy and increased in early- and late-onset preeclampsia. The source of ESM-1 is probably not the placenta, but most likely maternal endothelial cells.

Purinergic regulation of brain catecholamine neurotransmission: In vivo electrophysiology and microdialysis study in rats.

It was previously reported that adenosine-2A (A2A) receptors interact with dopamine-2 (D2) receptors on a molecular level. The aim of the current study was to investigate the functional output of this interaction. In vivo microdialysis was used to assess the effects of an antagonist of A2A receptors, ZM 241385, and an antagonist of D2 receptors haloperidol, either alone or in combination, on brain catecholamine levels. It was found that ZM 241385 did not alter catecholamine levels by its own, but potentiated haloperidol-induced dopamine and norepinephrine release in the nucleus accumbens and prefrontal cortex, respectively. In vivo electrophysiology was used to assess the effect of an agonist (CGS 216820) and an antagonist (ZM 241385) of A2A receptors on the excitability of dopamine and norepinephrine neurons. It was found that CGS 216820 dose-dependently inhibited dopamine and norepinephrine neurons and ZM 241385 reversed this inhibition. In conclusion, those A2A receptors modulate brain catecholamine transmission, and this modulation is mediated, at least in part, via the regulation of excitability of norepinephrine and dopamine neurons. The ability of antagonists of A2A receptors to potentiate the effect of haloperidol on brain norepinephrine and dopamine levels may enhance its clinical efficacy as an antipsychotic drug.

Development of a Rat Plasma and Brain Extracellular Fluid Pharmacokinetic Model for Bupropion and Hydroxybupropion Based on Microdialysis Sampling, and Application to Predict Human Brain Concentrations.

Administration of bupropion [(±)-2-(tert-butylamino)-1-(3-chlorophenyl)propan-1-one] and its preformed active metabolite, hydroxybupropion [(±)-1-(3-chlorophenyl)-2-[(1-hydroxy-2-methyl-2-propanyl)amino]-1-propanone], to rats with measurement of unbound concentrations by quantitative microdialysis sampling of plasma and brain extracellular fluid was used to develop a compartmental pharmacokinetics model to describe the blood-brain barrier transport of both substances. The population model revealed rapid equilibration of both entities across the blood-brain barrier, with resultant steady-state brain extracellular fluid/plasma unbound concentration ratio estimates of 1.9 and 1.7 for bupropion and hydroxybupropion, respectively, which is thus indicative of a net uptake asymmetry. An overshoot of the brain extracellular fluid/plasma unbound concentration ratio at early time points was observed with bupropion; this was modeled as a time-dependent uptake clearance of the drug across the blood-brain barrier. Translation of the model was used to predict bupropion and hydroxybupropion exposure in human brain extracellular fluid after twice-daily administration of 150 mg bupropion. Predicted concentrations indicate that preferential inhibition of the dopamine and norepinephrine transporters by the metabolite, with little to no contribution by bupropion, would be expected at this therapeutic dose. Therefore, these results extend nuclear imaging studies on dopamine transporter occupancy and suggest that inhibition of both transporters contributes significantly to bupropion's therapeutic efficacy.

Interaction Between Brain Histamine and Serotonin, Norepinephrine, and Dopamine Systems: In Vivo Microdialysis and Electrophysiology Study.

Brain monoamines (serotonin, norepinephrine, dopamine, and histamine) play an important role in emotions, cognition, and pathophysiology and treatment of mental disorders. The interactions between serotonin, norepinephrine, and dopamine were studied in numerous works; however, histamine system received less attention. The aim of this study was to investigate the interactions between histamine and other monoamines, using in vivo microdialysis and electrophysiology. It was found that the inverse agonist of histamine-3 receptors, thioperamide, increased the firing activity of dopamine neurons in the ventral tegmental area. Selective agonist of histamine-3 receptors, immepip, reversed thiperamide-induced stimulation of firing activity of dopamine neurons. The firing rates of serotonin and norpeinephrine neurons were not attenuated by immepip or thioperamide. Thioperamide robustly and significantly increased extracellular concentrations of serotonin, norepinephrine, and dopamine in the rat prefrontal cortex and slightly increased norepinephrine and dopamine levels in the tuberomammillary nucleus of the hypothalamus. It can be concluded that histamine stimulates serotonin, norepinephrine, and dopamine transmission in the brain. Modulation of firing of dopamine neurons is a key element in functional interactions between histamine and other monoamines. Antagonists of histamine-3 receptors, because of their potential ability to stimulate monoamine neurotransmission, might be beneficial in the treatment of mental disorders.

Prediction of brain clozapine and norclozapine concentrations in humans from a scaled pharmacokinetic model for rat brain and plasma pharmacokinetics.

BACKGROUND: Clozapine is highly effective in treatment-resistant schizophrenia, although, there remains significant variability in the response to this drug. To better understand this variability, the objective of this study was to predict brain extracellular fluid (ECF) concentrations and receptor occupancy of clozapine and norclozapine in human central nervous system by translating plasma and brain ECF pharmacokinetic (PK) relationships in the rat and coupling these with known human disposition of clozapine in the plasma. METHODS: Unbound concentrations of clozapine and norclozapine were measured in rat brain ECF using quantitative microdialysis after subcutaneous administration of a 10 mg/kg single dose of clozapine or norclozapine. These data were linked with plasma concentrations obtained in the same rats to develop a plasma-brain ECF compartmental model. Parameters describing brain ECF disposition were then allometrically scaled and linked with published human plasma PK to predict human ECF concentrations. Subsequently, prediction of human receptor occupancy at several CNS receptors was based on an effect model that related the predicted ECF concentrations to published concentration-driven receptor occupancy parameters. RESULTS: A one compartment model with first order absorption and elimination best described clozapine and norclozapine plasma concentrations in rats. A delay in the transfer of clozapine and norclozapine from plasma to the brain ECF compartment was captured using a transit compartment model approach. Human clozapine and norclozapine concentrations in brain ECF were simulated, and from these the median percentage of receptor occupancy of dopamine-2, serotonin-2A, muscarinic-1, alpha-1 adrenergic, alpha-2 adrenergic and histamine-1 for clozapine, and dopamine-2 for norclozapine were consistent with values reported in the literature. CONCLUSIONS: A PK model that relates clozapine and norclozapine disposition in rat plasma and brain, including blood-brain barrier transport, was developed. Using allometry and published human plasma PK, the model was successfully translated to predict clozapine and norclozapine concentrations and accordant receptor occupancy of both agents in human brain. These predicted exposure and occupancy measures at several receptors that bind clozapine may be employed to extend our understanding of clozapine's complex behavioral effects in humans.

Lentiviral delivery of a vesicular glutamate transporter 1 (VGLUT1)-targeting short hairpin RNA vector into the mouse hippocampus impairs cognition.

Glutamate is the principle excitatory neurotransmitter in the mammalian brain, and dysregulation of glutamatergic neurotransmission is implicated in the pathophysiology of several psychiatric and neurological diseases. This study utilized novel lentiviral short hairpin RNA (shRNA) vectors to target expression of the vesicular glutamate transporter 1 (VGLUT1) following injection into the dorsal hippocampus of adult mice, as partial reductions in VGLUT1 expression should attenuate glutamatergic signaling and similar reductions have been reported in schizophrenia. The VGLUT1-targeting vector attenuated tonic glutamate release in the dorsal hippocampus without affecting GABA, and selectively impaired novel object discrimination (NOD) and retention (but not acquisition) in the Morris water maze, without influencing contextual fear-motivated learning or causing any adverse locomotor or central immune effects. This pattern of cognitive impairment is consistent with the accumulating evidence for functional differentiation along the dorsoventral axis of the hippocampus, and supports the involvement of dorsal hippocampal glutamatergic neurotransmission in both spatial and nonspatial memory. Future use of this nonpharmacological VGLUT1 knockdown mouse model could improve our understanding of glutamatergic neurobiology and aid assessment of novel therapies for cognitive deficits such as those seen in schizophrenia.

Therapeutic doses of antidepressants are projected not to inhibit human α4ß2 nicotinic acetylcholine receptors.

Inhibition of central α4ß2 nAChRs by antidepressants, proposed to contribute to their clinical efficacy, was assessed for monoamine reuptake inhibitors (amitriptyline, nortriptyline, fluoxetine, sertraline, paroxetine, citalopram) by comparing projected human unbound brain drug concentrations (Cu,b) at therapeutic doses with concentrations that inhibit human α4ß2 nAChRs in vitro. Inhibitory concentrations (IC50) were determined by patch clamp and ranged from 0.8-3.2 µM, except for nortriptyline (IC50 = 100 nM). Cu,b values were calculated from human unbound plasma drug concentrations (Cu,p) and rat-derived brain-to-plasma and extracellular fluid-to-plasma ratios for the unbound drug, which are near unity, due to much higher brain tissue binding than plasma protein binding of these drugs. Accordingly in humans, antidepressant Cu,b are projected to essentially equal Cu,p, with average values from 3-87 nM, which are 30-to-250-fold below their IC50 concentrations. Based on our model, monoaminergic antidepressants minimally inhibit central nAChRs and it is unlikely that α4ß2 nAChR antagonism contributes to their antidepressant activity. Nortriptyline is an exception with a Cu,b that is 2-fold below its IC50, which is comparable to the nAChR antagonist (±)-mecamylamine, for which Cu,b is 4-fold below its IC50; both drugs will inhibit a substantial fraction of α4ß2 nAChRs. The Cu,b of the α4ß2 nAChR partial agonist varenicline, which has antidepressant-like activity in a murine model, is higher than its IC50 and varenicline is projected to cause ~70% inhibition of α4ß2 nAChRs. Taken together these data may help explain the negative outcome of recent antidepressant augmentation trials with mecamylamine and the partial agonist CP-601927.

Lu AA21004, a novel multimodal antidepressant, produces regionally selective increases of multiple neurotransmitters--a rat microdialysis and electrophysiology study.

The monoaminergic network, including serotonin (5-HT), norepinephrine (NE), and dopamine (DA) pathways, is highly interconnected and has a well-established role in mood disorders. Preclinical research suggests that 5-HT receptor subtypes, including 5-HT1A, 5-HT1B, 5-HT3, and 5-HT7 receptors as well as the 5-HT transporter (SERT), may have important roles in treating depression. This study evaluated the neuropharmacological profile of Lu AA21004, a novel multimodal antidepressant combining 5-HT3 and 5-HT7 receptor antagonism, 5-HT1B receptor partial agonism, 5-HT1A receptor agonism, and SERT inhibition in recombinant cell lines. Extracellular 5-HT, NE and DA levels were evaluated in the ventral hippocampus (vHC), medial prefrontal cortex (mPFC) and nucleus accumbens (NAc) after acute and subchronic treatment with Lu AA21004 or escitalopram. The acute effects of LuAA21004 on NE and DA neuronal firing were also evaluated in the locus coeruleus (LC) and ventral tegmental area (VTA), respectively. Acute Lu AA21004 dose-dependently increased 5-HT in the vHC, mPFC and NAc. Maximal 5-HT levels in the vHC were higher than those in the mPFC. Furthermore, mPFC 5-HT levels were increased at low SERT occupancy levels. In the vHC and mPFC, but not the NAc, high Lu AA21004 doses increased NE and DA levels. Lu AA21004 slightly decreased LC NE neuronal firing and had no effect on VTA DA firing. Results are discussed in context of occupancy at 5-HT3, 5-HT1B and 5-HT1A receptors and SERT. In conclusion, Lu AA21004, acting via two pharmacological modalities, 5-HT receptor modulation and SERT inhibition, results in a brain region-dependent increase of multiple neurotransmitter concentrations.

Improved preclinical cardiovascular therapeutic indices with long-term inhibition of norepinephrine reuptake using reboxetine.

Norepinephrine reuptake inhibitors (NRIs) acutely increase norepinephrine (NE) levels, but therapeutic antidepressant activity is only observed after weeks of treatment because central NE levels progressively increase during continued drug exposure. Similarly, while NRIs acutely increase blood pressure (BP) and heart rate (HR) due to enhanced sympathetic neurotransmission, chronic treatment changes the responsiveness of the central noradrenergic system and suppresses these effects via autonomic regulation. To better understand the relationship between NE increases and cardiovascular safety, we investigated acute and chronic effects of the NRI reboxetine on central NE release and on BP and HR and electrical alternans, a measure of arrhythmia liability, in guinea pigs. NE release was assessed by microdialysis in medial prefrontal cortex (mPFC) and hypothalamic paraventricular nucleus (PVN); BP and HR were measured by telemetry. Animals were treated for 28 days with 15 mg/kg/day of reboxetine or vehicle via an osmotic minipump and then challenged with acute intravenous doses of reboxetine. Animals chronically treated with reboxetine had 2-fold higher extracellular basal NE levels in mPFC and PVN compared to basal levels after chronic vehicle treatment. BP was significantly increased after the first day of treatment, and gradually returned to vehicle levels by day 21. These data indicate that chronic NRI treatment may lead to an increase in central NE levels and a concomitant reduction in BP based on exposure-response curves compared to vehicle treatment, suggesting a larger separation between preclinical estimates of efficacy vs. safety compared to acute NRI treatment.

Microdialysis evaluation of clozapine and N-desmethylclozapine pharmacokinetics in rat brain.

A significant barrier to realization of the full potential of clozapine as a therapeutic agent in the treatment of schizophrenia is the substantial interpatient variability that exists along the therapeutic continuum of no response-efficacious response-adverse response. Genetic polymorphisms that manifest as highly variable pharmacodynamic and pharmacokinetic measures are its expected causes. To support investigations that seek to understand these causes, the plasma and central nervous system pharmacokinetics of clozapine were determined in rats, the latter using microdialysis sampling. Results obtained with clozapine and N-desmethylclozapine, a pharmacologically active human metabolite that was administered to a separate group of animals, support a conclusion of net carrier-mediated efflux of both compounds across the blood-brain barrier. These results are supported by the replication of published findings regarding the passive transport and net efflux transport of two model compounds, escitalopram and risperidone, respectively. The results obtained with clozapine and N-desmethylclozapine are considered a first step in the development of preclinical pharmacokinetic-pharmacodynamic models that will support deeper mechanistic studies of clozapine in in vivo pharmacology, as well as the development of translational models that augment pharmacogenetic investigations that seek to improve the safety and efficacy of clozapine therapeutic intervention in the treatment of schizophrenia.

S32212, a novel serotonin type 2C receptor inverse agonist/α2-adrenoceptor antagonist and potential antidepressant: II. A behavioral, neurochemical, and electrophysiological characterization.

The present studies characterized the functional profile of N-[4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]-1,2-dihydro-3-H-benzo[e]indole-3-carboxamide) (S32212), a combined serotonin (5-HT)(2C) receptor inverse agonist and α(2)-adrenoceptor antagonist that also possesses 5-HT(2A) antagonist properties (J Pharmacol Exp Ther 340:750-764, 2012). Upon parenteral and/or oral administration, dose-dependent (0.63-40.0 mg/kg) actions were observed in diverse procedures. Both acute and subchronic administration of S32212 reduced immobility time in a forced-swim test in rats. Acutely, it also suppressed marble burying and aggressive behavior in mice. Long-term administration of S32212 was associated with rapid (1 week) and sustained (5 weeks) normalization of sucrose intake in rats exposed to chronic mild stress and with elevated levels of mRNA encoding brain-derived neurotrophic factor in hippocampus and amygdala (2 weeks). S32212 accelerated the firing rate of adrenergic perikarya in the locus coeruleus and elevated dialysis levels of noradrenaline in the frontal cortex and hippocampus of freely moving rats. S32212 also elevated the frontocortical levels of dopamine and acetylcholine, whereas 5-HT, amino acids, and histamine were unaffected. These neurochemical actions were paralleled by "promnemonic" properties: blockade of scopolamine-induced deficits in radial maze performance and social recognition and reversal of delay-induced impairments in social recognition, social novelty discrimination, and novel object recognition. It also showed anxiolytic actions in a Vogel conflict procedure. Furthermore, in an electroencephalographic study of sleep architecture, S32212 enhanced slow-wave and rapid eye movement sleep, while decreasing waking. Finally, chronic administration of S32212 neither elevated body weight nor perturbed sexual behavior in male rats. In conclusion, S32212 displays a functional profile consistent with improved mood and cognitive performance, together with satisfactory tolerance.

The role of cortical and hypothalamic histamine-3 receptors in the modulation of central histamine neurotransmission: an in vivo electrophysiology and microdialysis study.

The current study aimed to investigate the effect of histamine-3 (H(3)) receptors, expressed in the tuberomammillary nucleus (TMN) of the hypothalamus and in the prefrontal cortex (PFC), on histamine neurotransmission in the rat brain. The firing activity of histamine neurons in the TMN was measured using in vivo extracellular single-unit electrophysiology, under propofol anesthesia. Extracellular histamine levels were determined using the dual (PFC and TMN) probe microdialysis, in freely-moving animals. Histamine levels in dialysates were determined using high-performance liquid chromatography (HPLC) and fluorescence detection. It was found that systemic administration of the selective H(3)-agonist, immepip, decreases, and the reverse H(3) /H(4)-agonist, thioperamide, increases the firing activity of histamine neurons in the TMN and the release of histamine in TMN and PFC. Local perfusion of immepip into the TMN increased, and thioperamide decreased, histamine levels in the TMN but not in the PFC. Local perfusion of immepip into the PFC, however, decreased extracellular histamine levels in both TMN and PFC. It can be concluded that brain H(3) receptors, and especially those expressed in the PFC, play an important role in the autoregulation of histamine neurotransmission. It is possible that H(3) receptors in the PFC are expressed on pyramidal neurons projecting to the TMN, and activation of these receptors diminishes glutamate excitatory input from PFC to the TMN. As the brain histamine system has a role in pathophysiology of psychotic, affective, cognitive, sleep and eating disorders, H(3) receptors are potential targets for future CNS medications.

CB-1 receptors modulate the effect of the selective serotonin reuptake inhibitor, citalopram on extracellular serotonin levels in the rat prefrontal cortex.

A large percentage of depressed individuals use drugs of abuse, like cannabis. This study investigates the impact of cannabis on the pharmacological effects of the antidepressant citalopram. Using microdialysis in the prefrontal cortex of rats we monitored serotonin levels before and after cannabinoid (WIN55,212-2 or rimonabant) and citalopram administration. Stimulating CB-1 decreased the effect of citalopram on increasing serotonin levels in the prefrontal cortex. Blocking CB-1 augmented this effect of citalopram. Although repeating these experiments in a chronical setting is recommended the present results might have implication for the clinical effects of citalopram.