The Dopamine D1 Receptor Positive Allosteric Modulator Mevidalen (LY3154207) Enhances Wakefulness in the Humanized D1 Mouse and in Sleep-Deprived Healthy Male Volunteers.

Dopamine (DA) plays a key role in several central functions including cognition, motor activity, and wakefulness. Although efforts to develop dopamine receptor 1 (D1) agonists have been challenging, a positive allosteric modulator represents an attractive approach with potential better drug-like properties. Our previous study demonstrated an acceptable safety and tolerability profile of the dopamine receptor 1 positive allosteric modulator (D1PAM) mevidalen (LY3154207) in single and multiple ascending dose studies in healthy volunteers (Wilbraham et al., 2021). Herein, we describe the effects of mevidalen on sleep and wakefulness in humanized dopamine receptor 1 (hD1) mice and in sleep-deprived healthy male volunteers. Mevidalen enhanced wakefulness (latency to fall asleep) in the hD1 mouse in a dose dependent [3-100 mg/kg, orally (PO)] fashion when measured during the light (zeitgeber time 5) and predominantly inactive phase. Mevidalen promoted wakefulness in mice after prior sleep deprivation and delayed sleep onset by 5.5- and 15.2-fold compared with vehicle-treated animals, after the 20 and 60 mg/kg PO doses, respectively, when compared with vehicle-treated animals. In humans, mevidalen demonstrated a dose-dependent increase in latency to sleep onset as measured by the multiple sleep latency test and all doses (15, 30, and 75 mg) separated from placebo at the first 2-hour postdose time point with a circadian effect at the 6-hour postdose time point. Sleep wakefulness should be considered a translational biomarker for the dopamine receptor 1 positive allosteric modulator mechanism. SIGNIFICANCE STATEMENT: This is the first translational study describing the effects of a selective dopamine receptor 1 positive allosteric modulator (D1PAM) on sleep and wakefulness in the human dopamine receptor 1 mouse and in sleep-deprived healthy male volunteers. In both species, drug exposure correlated with sleep latency, supporting the use of sleep-wake activity as a translational central biomarker for D1PAM. Wake-promoting effects of D1PAMs may offer therapeutic opportunities in several conditions, including sleep disorders and excessive daytime sleepiness related to neurodegenerative disorders.

Quantitative propagation of assembled human Tau from Alzheimer's disease brain in microfluidic neuronal cultures.

Tau aggregation and hyperphosphorylation is a key neuropathological hallmark of Alzheimer's disease (AD), and the temporospatial spread of Tau observed during clinical manifestation suggests that Tau pathology may spread along the axonal network and propagate between synaptically connected neurons. Here, we have developed a cellular model that allows the study of human AD-derived Tau propagation from neuron to neuron using microfluidic devices. We show by using high-content imaging techniques and an in-house developed interactive computer program that human AD-derived Tau seeds rodent Tau that propagates trans-neuronally in a quantifiable manner in a microfluidic culture model. Moreover, we were able to convert this model to a medium-throughput format allowing the user to handle 16 two-chamber devices simultaneously in the footprint of a standard 96-well plate. Furthermore, we show that a small molecule inhibitor of aggregation can block the trans-neuronal transfer of Tau aggregates, suggesting that the system can be used to evaluate mechanisms of Tau transfer and find therapeutic interventions.

Mechanism of action deconvolution of the small-molecule pathological tau aggregation inhibitor Anle138b.

BACKGROUND: A key histopathological hallmark of Alzheimer's disease (AD) is the presence of neurofibrillary tangles of aggregated microtubule-associated protein tau in neurons. Anle138b is a small molecule which has previously shown efficacy in mice in reducing tau aggregates and rescuing AD disease phenotypes. METHODS: In this work, we employed bioinformatics analysis-including pathway enrichment and causal reasoning-of an in vitro tauopathy model. The model consisted of cultured rat cortical neurons either unseeded or seeded with tau aggregates derived from human AD patients, both of which were treated with Anle138b to generate hypotheses for its mode of action. In parallel, we used a collection of human target prediction models to predict direct targets of Anle138b based on its chemical structure. RESULTS: Combining the different approaches, we found evidence supporting the hypothesis that the action of Anle138b involves several processes which are key to AD progression, including cholesterol homeostasis and neuroinflammation. On the pathway level, we found significantly enriched pathways related to these two processes including those entitled "Superpathway of cholesterol biosynthesis" and "Granulocyte adhesion and diapedesis". With causal reasoning, we inferred differential activity of SREBF1/2 (involved in cholesterol regulation) and mediators of the inflammatory response such as NFKB1 and RELA. Notably, our findings were also observed in Anle138b-treated unseeded neurons, meaning that the inferred processes are independent of tau pathology and thus represent the direct action of the compound in the cellular system. Through structure-based ligand-target prediction, we predicted the intracellular cholesterol carrier NPC1 as well as NF-κB subunits as potential targets of Anle138b, with structurally similar compounds in the model training set known to target the same proteins. CONCLUSIONS: This study has generated feasible hypotheses for the potential mechanism of action of Anle138b, which will enable the development of future molecular interventions aiming to reduce tau pathology in AD patients.

A human tau seeded neuronal cell model recapitulates molecular responses associated with Alzheimer's disease.

Cellular models recapitulating features of tauopathies are useful tools to investigate the causes and consequences of tau aggregation and the identification of novel treatments. We seeded rat primary cortical neurons with tau isolated from Alzheimer's disease brains to induce a time-dependent increase in endogenous tau inclusions. Transcriptomics of seeded and control cells identified 1075 differentially expressed genes (including 26 altered at two time points). These were enriched for lipid/steroid metabolism and neuronal/glial cell development genes. 50 genes were correlated with tau inclusion formation at both transcriptomic and proteomic levels, including several microtubule and cytoskeleton-related proteins such as Tubb2a, Tubb4a, Nefl and Snca. Several genes (such as Fyn kinase and PTBP1, a tau exon 10 repressor) interact directly with or regulate tau. We conclude that this neuronal model may be a suitable platform for high-throughput screens for target or hit compound identification and validation.

Development of an Electrophysiological Assay for Kv7 Modulators on IonWorks Barracuda.

Relief from chronic pain continues to represent a large unmet need. The voltage-gated potassium channel Kv7.2/7.3, also known as KCNQ2/3, is a key contributor to the control of resting membrane potential and excitability in nociceptive neurons and represents a promising target for potential therapeutics. In this study, we present a medium throughput electrophysiological assay for the identification and characterization of modulators of Kv7.2/7.3 channels, using the IonWorks Barracuda™ automated voltage clamp platform. The assay combines a family of voltage steps used to construct conductance curves with a unique analysis method. Kv7.2/7.3 modulators shift the activation voltage and/or change the maximal conductance of the current, and both parameters have been used to quantify compound mediated effects. Both effects are expected to modulate neuronal excitability in vivo. The analysis method described assigns a single potency value that combines changes in activation voltage and maximal conductance and is expected to predict compound mediated changes in excitability.

Pharmacological Modulation of Sleep Homeostasis in Rat: Novel Effects of an mGluR2/3 Antagonist.

Increasing vigilance without incurring the negative consequences of extended wakefulness such as daytime sleepiness and cognitive impairment is a major challenge in treating many sleep disorders. The present work compares two closely related mGluR2/3 antagonists LY3020371 and LY341495 with two well-known wake-promoting compounds caffeine and d-amphetamine. Sleep homeostasis properties were explored in male Wistar rats by manipulating levels of wakefulness via (1) physiological sleep restriction (SR), (2) pharmacological action, or (3) a combination of these. A two-phase nonlinear mixed-effects model combining a quadratic and exponential function at an empirically estimated join point allowed the quantification of wake-promoting properties and any subsequent sleep rebound. A simple response latency task (SRLT) following SR assessed functional capacity of sleep-restricted animals treated with our test compounds. Caffeine and d-amphetamine increased wakefulness with a subsequent full recovery of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep and were unable to fully reverse SR-induced impairments in SRLT. In contrast, LY3020371 increased wakefulness with no subsequent elevation of NREM sleep, delta power, delta energy, or sleep bout length and count, yet REM sleep recovered above baseline levels. Prior sleep pressure obtained using an SR protocol had no impact on the wake-promoting effect of LY3020371 and NREM sleep rebound remained blocked. Furthermore, LY341495 increased functional capacity across SRLT measures following SR. These results establish the critical role of glutamate in sleep homeostasis and support the existence of independent mechanisms for NREM and REM sleep homeostasis.

A Bayesian gene network reveals insight into the JAK-STAT pathway in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a chronic, remitting, and relapsing, inflammatory disease involving multiple organs, which exhibits abnormalities of both the innate and adaptive immune responses. A limited number of transcriptomic studies have characterized the gene pathways involved in SLE in an attempt to identify the key pathogenic drivers of the disease. In order to further advance our understanding of the pathogenesis of SLE, we used a novel Bayesian network algorithm to hybridize knowledge- and data-driven methods, and then applied the algorithm to build an SLE gene network using transcriptomic data from 1,760 SLE patients' RNA from the two tabalumab Phase III trials (ILLUMINATE-I & -II), the largest SLE RNA dataset to date. Further, based on the gene network, we carried out hub- and key driver-gene analyses for gene prioritization. Our analyses identified that the JAK-STAT pathway genes, including JAK2, STAT1, and STAT2, played essential roles in SLE pathogenesis, and reaffirmed the recent discovery of pathogenic relevance of JAK-STAT signaling in SLE. Additionally, we showed that other genes, such as IRF1, IRF7, PDIA4, FAM72C, TNFSF10, DHX58, SIGLEC1, and PML, may be also important in SLE and serve as potential therapeutic targets for SLE. In summary, using a hybridized network construction approach, we systematically investigated gene-gene interactions based on their transcriptomic profiles, prioritized genes based on their importance in the network structure, and revealed new insights into SLE activity.

Expression-based drug screening of neural progenitor cells from individuals with schizophrenia.

A lack of biologically relevant screening models hinders the discovery of better treatments for schizophrenia (SZ) and other neuropsychiatric disorders. Here we compare the transcriptional responses of 8 commonly used cancer cell lines (CCLs) directly with that of human induced pluripotent stem cell (hiPSC)-derived neural progenitor cells (NPCs) from 12 individuals with SZ and 12 controls across 135 drugs, generating 4320 unique drug-response transcriptional signatures. We identify those drugs that reverse post-mortem SZ-associated transcriptomic signatures, several of which also differentially regulate neuropsychiatric disease-associated genes in a cell type (hiPSC NPC vs. CCL) and/or a diagnosis (SZ vs. control)-dependent manner. Overall, we describe a proof-of-concept application of transcriptomic drug screening to hiPSC-based models, demonstrating that the drug-induced gene expression differences observed with patient-derived hiPSC NPCs are enriched for SZ biology, thereby revealing a major advantage of incorporating cell type and patient-specific platforms in drug discovery.

Author Correction: Expression-based drug screening of neural progenitor cells from individuals with schizophrenia.

In the originally published version of this Article, the affiliation details for Eric E. Schadt and Radoslav Savic incorrectly omitted 'Sema4, a Mount Sinai venture, Stamford, Connecticut, USA'. This has been corrected in both the PDF and HTML versions of the Article.

Genome-wide RNAseq study of the molecular mechanisms underlying microglia activation in response to pathological tau perturbation in the rTg4510 tau transgenic animal model.

BACKGROUND: Activation of microglia, the resident immune cells of the central nervous system, is a prominent pathological hallmark of Alzheimer's disease (AD). However, the gene expression changes underlying microglia activation in response to tau pathology remain elusive. Furthermore, it is not clear how murine gene expression changes relate to human gene expression networks. METHODS: Microglia cells were isolated from rTg4510 tau transgenic mice and gene expression was profiled using RNA sequencing. Four age groups of mice (2-, 4-, 6-, and 8-months) were analyzed to capture longitudinal gene expression changes that correspond to varying levels of pathology, from minimal tau accumulation to massive neuronal loss. Statistical and system biology approaches were used to analyze the genes and pathways that underlie microglia activation. Differentially expressed genes were compared to human brain co-expression networks. RESULTS: Statistical analysis of RNAseq data indicated that more than 4000 genes were differentially expressed in rTg4510 microglia compared to wild type microglia, with the majority of gene expression changes occurring between 2- and 4-months of age. These genes belong to four major clusters based on their temporal expression pattern. Genes involved in innate immunity were continuously up-regulated, whereas genes involved in the glutamatergic synapse were down-regulated. Up-regulated innate inflammatory pathways included NF-κB signaling, cytokine-cytokine receptor interaction, lysosome, oxidative phosphorylation, and phagosome. NF-κB and cytokine signaling were among the earliest pathways activated, likely driven by the RELA, STAT1 and STAT6 transcription factors. The expression of many AD associated genes such as APOE and TREM2 was also altered in rTg4510 microglia cells. Differentially expressed genes in rTg4510 microglia were enriched in human neurodegenerative disease associated pathways, including Alzheimer's, Parkinson's, and Huntington's diseases, and highly overlapped with the microglia and endothelial modules of human brain transcriptional co-expression networks. CONCLUSION: This study revealed temporal transcriptome alterations in microglia cells in response to pathological tau perturbation and provides insight into the molecular changes underlying microglia activation during tau mediated neurodegeneration.

Preclinical profile of a dopamine D1 potentiator suggests therapeutic utility in neurological and psychiatric disorders.

DETQ, an allosteric potentiator of the dopamine D1 receptor, was tested in therapeutic models that were known to respond to D1 agonists. Because of a species difference in affinity for DETQ, all rodent experiments used transgenic mice expressing the human D1 receptor (hD1 mice). When given alone, DETQ reversed the locomotor depression caused by a low dose of reserpine. DETQ also acted synergistically with L-DOPA to reverse the strong hypokinesia seen with a higher dose of reserpine. These results indicate potential as both monotherapy and adjunct treatment in Parkinson's disease. DETQ markedly increased release of both acetylcholine and histamine in the prefrontal cortex, and increased levels of histamine metabolites in the striatum. In the hippocampus, the combination of DETQ and the cholinesterase inhibitor rivastigmine increased ACh to a greater degree than either agent alone. DETQ also increased phosphorylation of the AMPA receptor (GluR1) and the transcription factor CREB in the striatum, consistent with enhanced synaptic plasticity. In the Y-maze, DETQ increased arm entries but (unlike a D1 agonist) did not reduce spontaneous alternation between arms at high doses. DETQ enhanced wakefulness in EEG studies in hD1 mice and decreased immobility in the forced-swim test, a model for antidepressant-like activity. In rhesus monkeys, DETQ increased spontaneous eye-blink rate, a measure that is known to be depressed in Parkinson's disease. Together, these results provide support for potential utility of D1 potentiators in the treatment of several neuropsychiatric disorders, including Parkinson's disease, Alzheimer's disease, cognitive impairment in schizophrenia, and major depressive disorder.

Electroencephalographic, cognitive, and neurochemical effects of LY3130481 (CERC-611), a selective antagonist of TARP-γ8-associated AMPA receptors.

6-[(1S)-1-[1-[5-(2-hydroxyethoxy)-2-pyridyl]pyrazol-3-yl]ethyl]-3H-1,3-benzothiazol-2-one (LY3130481 or CERC-611) is a selective antagonist of AMPA receptors containing transmembrane AMPA receptor regulatory protein (TARP) γ-8. This molecule has been characterized as a potent and efficacious anticonvulsant in an array of acute and chronic epilepsy models in rodents. The present set of experiments was designed to assess the effects of LY3130481 on the electroencephelogram (EEG), cognitive function, and neurochemical outflow. LY3130481 disrupted food-maintained responding in rats and spontaneous alternation in a Y-maze in mice. In rat fear conditioning, LY3130481 caused a deficit in trace (hippocampal-dependent), but not in delay fear conditioning. Although these effects on cognitive performances were observed, the known cognitive-impairing anticonvulsant, topiramate, did not always produce deficits under these assay conditions. LY3130481 produced modest increases in wake times in rats. In addition, LY3130481 was able to attenuate some impairing effects of standard antiepileptic drugs. The motor-impairing effects of the lacosamide were attenuated by LY3130481 as was the decrease in non-rapid-eye movement sleep induced by carbamazepine. Evaluation of the effect of LY3130481 on neurotransmitter and metabolite efflux in the rat medial prefrontal cortex, using in vivo microdialysis, revealed significant increases in the pro-cognitive and wake-promoting neurotransmitters, histamine and acetylcholine, as well as in serotonin, telemethylhistamine, 5-HIAA, HVA and MHPG. LY3130481 thus presents a novel behavioral profile that will have to be evaluated in patients to fully appreciate its implications for therapeutics. LY3130481 is currently under clinical development as CERC-611 as an antiepileptic.

Analgesic effects of serotonergic, noradrenergic or dual reuptake inhibitors in the carrageenan test in rats: evidence for synergism between serotonergic and noradrenergic reuptake inhibition.

The efficacy of antidepressant drugs with serotonergic, noradrenergic, or dual reuptake inhibition was evaluated in reversing carrageenan-induced thermal hyperalgesia and mechanical allodynia in rats. Duloxetine (1-30mg/kg, i.p.), a balanced serotonergic-noradrenergic reuptake inhibitor (SNRI), was equiefficacious and more potent than the SNRI venlafaxine (3-100mg/kg, i.p.) in reversing both thermal hyperalgesia and mechanical allodynia induced by carrageenan. In addition, the selective noradrenergic reuptake inhibitors (NRIs) thionisoxetine (0.03-10mg/kg, i.p.) and desipramine (1-30mg/kg, i.p.) also produced complete reversals of carrageenan-induced thermal hyperalgesia. However, only thionisoxetine exhibited a greater than 80% reversal of the carrageenan-induced mechanical allodynia. In contrast, the selective serotonergic reuptake inhibitors (SSRIs) paroxetine, sertraline, and fluoxetine (0.3-10mg/kg i.p.) had little or no effect in the carrageenan model. In order to understand whether the observed enhanced effectiveness of the dual SNRIs was due to a possible synergism between serotonergic and noradrenergic reuptake inhibition, the effects of the NRI thionisoxetine alone and in combination with an inactive dose of the SSRI fluoxetine were determined. In the presence of fluoxetine, the potency of thionisoxetine in reversing carrageenan-induced hyperalgesia and allodynia was significantly increased by approximately 100-fold and brain concentrations of thionisoxetine were increased by 1.1- to 5-fold. The present data indicate fluoxetine pharmacodynamically potentiated the analgesic effects of thionisoxetine over and above a metabolic interaction between these two drugs. The present findings thus indicate that, in the carrageenan model, dual serotonergic-noradrenergic reuptake inhibition by dual SNRIs, or SSRI-NRI combinations, produces synergistic analgesic efficacy.

A comparison of assay performance measures in screening assays: signal window, Z' factor, and assay variability ratio.

In this article, the authors compare the assay performance measures, signal window, Z' factor, and assay variability ratio. They examine their mathematical formulae for similarities and differences, describe their statistical sampling properties using the results of a computer simulation, and illustrate their use with example data. Based on these results, the authors recommend the Z' factor as a preferred measure of assay performance for screening assays and point out that none of these measures are adequate for characterizing concentration-response assays.

The minimum significant ratio: a statistical parameter to characterize the reproducibility of potency estimates from concentration-response assays and estimation by replicate-experiment studies.

The authors show by illustration that procedures used to validate the reliability of single-concentration high-throughput screens such as the signal window and Z' factor do not ensure sufficient reliability in potency estimates from concentration response assays. They develop the minimum significant ratio as a statistical parameter to characterize the fold change between 2 compounds run in the same experiment that can be considered a real difference and use this parameter to characterize the reliability of the assay. They adapt methods described by Bland and Altman to develop a simple set of 2 experiments to estimate the minimum significant ratio and show that this protocol can identify assays that lack reproducibility. The methods are then extended to validate the equivalency of the same assay run by multiple laboratories.

Advances in the genetics of schizophrenia: toward a network and pathway view for drug discovery.

The spectacular advance in our understanding of the genetic basis of schizophrenia through genome-wide association studies has the potential to identify new leads for drug treatment through improved understanding of disease pathophysiology. However, using these genetic associations successfully in drug development and patient stratification requires further target validation, particularly in understanding which gene(s) is causal in the disease, how the risk variants alter gene function and regulation, and how they fit into disease pathways and networks. If researchers consider the disease network as the target, they need to understand which genes should be targeted and in which modality, in order to modulate pathophysiology and obtain a beneficial effect for the patient. In the present article, we review recent genetic findings in schizophrenia and discuss how these might be validated with biology and integrated with epigenetic and transcriptome data to identify targets that lie within disease networks and pathways. This new understanding of disease biology will also facilitate the development of assays that recapitulate specific aspects of the disease using model organisms and cells. These assays can then be used in screening approaches, which manipulate disease networks or pathological processes to generate and test therapeutic strategies.

Myostatin Neutralization Results in Preservation of Muscle Mass and Strength in Preclinical Models of Tumor-Induced Muscle Wasting.

Skeletal muscle wasting occurs in a great majority of cancer patients with advanced disease and is associated with a poor prognosis and decreased survival. Myostatin functions as a negative regulator of skeletal muscle mass and has recently become a therapeutic target for reducing the loss of skeletal muscle and strength associated with clinical myopathies. We generated neutralizing antibodies to myostatin to test their potential use as therapeutic agents to attenuate the skeletal muscle wasting due to cancer. We show that our neutralizing antimyostatin antibodies significantly increase body weight, skeletal muscle mass, and strength in non-tumor-bearing mice with a concomitant increase in mean myofiber area. The administration of these neutralizing antibodies in two preclinical models of cancer-induced muscle wasting (C26 colon adenocarcinoma and PC3 prostate carcinoma) resulted in a significant attenuation of the loss of muscle mass and strength with no effect on tumor growth. We also show that the skeletal muscle mass- and strength-preserving effect of the antibodies is not affected by the coadministration of gemcitabine, a common chemotherapeutic agent, in both non-tumor-bearing mice and mice bearing C26 tumors. In addition, we show that myostatin neutralization with these antibodies results in the preservation of skeletal muscle mass following reduced caloric intake, a common comorbidity associated with advanced cancer. Our findings support the use of neutralizing antimyostatin antibodies as potential therapeutics for cancer-induced muscle wasting.

Activation of mesolimbic dopamine neurons during novel and daily limited access to palatable food is blocked by the opioid antagonist LY255582.

An analog of the trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine series (LY255582) exhibits high in vitro binding affinity and antagonist potency for the mu-, delta-, and kappa-opioid receptors. In vivo, LY255582 exhibits potent effects in reducing food intake and body weight in several rodent models of obesity. In the present study, we evaluated the effects of LY255582 to prevent the consumption of a highly palatable (HP) diet (a high-fat/high-carbohydrate diet) both when the food was novel and following daily limited access to the HP diet. Additionally, we examined the effects of consumption of the HP diet and of LY255582 treatment on mesolimbic dopamine (DA) signaling by in vivo microdialysis. Consumption of the HP diet increased extracellular DA levels within the nucleus accumbens (NAc) shell. Increased DA in the NAc shell was not related to the quantity of the HP diet consumed, and the DA response did not habituate following daily scheduled access to the HP diet. Interestingly, treatment with LY255582 inhibited consumption of the HP diet and the HP diet-associated increase in NAc shell DA levels. Moreover, the increased HP diet consumption observed following daily limited access to the HP diet was completely prevented by LY255582 treatment. LY255582 may be a useful tool in understanding the neural mechanisms involved in the reinforcement mechanisms regulating food intake.

Dopamine D1/5 receptor modulation of firing rate and bidirectional theta burst firing in medial septal/vertical limb of diagonal band neurons in vivo.

The medial septum/vertical limb of diagonal band complex (MS/vDB) consists of cholinergic, GABAergic, and glutamatergic neurons that project to the hippocampus and functionally regulate attention, memory, and cognitive processes. Using tyrosine hydroxlase (TH) immunocytochemistry and dark-field light microscopy, we found that the MS/vDB is innervated by a sparse network of TH-immunoreactive (putative catecholaminergic) terminals. MS/vDB neurons are known to fire in rhythmic theta burst frequency of 3-7 Hz to pace hippocampal theta rhythm. Extracellular single-unit recording in theta and non-theta firing MS/vDB neurons and antidromically identified MS/vDB-hippocampal neurons were made in urethan-anesthetized rats. Tail-pinch noxious stimuli and ventral tegmental area (VTA) stimulation (20 Hz) evoked spontaneous theta burst firing in MS/vDB neurons. Systemic D1/5 antagonists SCH23390 or SCH39166 (0.1 mg/kg iv) alone suppressed the spontaneous theta bursts, suggesting a tonic facilitatory endogenous dopamine D1 "tone" that modulates theta bursts in vivo. Activation of D1/5 receptor by dihydrexidine (10 mg/kg iv) led to an increase in mean firing rate in 60% of all theta and non-theta MS/vDB neurons with an increase in the number of theta bursts and spikes/burst in theta cells. In strong theta firing MS/vDB neurons, D1/5 receptor stimulation suppressed the occurrence of theta burst firing, whereas the overall increase in spontaneous mean firing rate remained. In low baseline theta MS/vDB neurons D1/5 receptor stimulation increases the occurrence of theta bursts along with a net increase in mean firing rate. Atropine injection consistently disrupts theta burst pattern and reduced the time spent in theta firing. Collectively, these data suggest that dopamine D1/5 stimulation enhances the mean firing rate of most MS/vDB neurons and also provides a state-dependent bidirectional modulation of theta burst occurrence. Some of these MS/vDB neurons may be cholinergic or GABAergic that may indirectly regulate theta rhythm in the hippocampus.

Effect of sampling frames on response rates in the WHO MONICA risk factor surveys.

Sample surveys are used to investigate occurrence and determinants of diseases in populations. Their reliability is influenced by quality of sampling frame and response rate. We investigated relationship between sampling frame type and response rates and assessed their impact on non-response bias, using data from the WHO MONICA Project, where 37 centres in 20 countries conducted sample surveys, employing the best locally available sampling frame. Sampling frames fell into three categories: Population registers (PR), electoral registers (ER), and health care registers (HR). Response rate (rrs) was factored into components reflecting quality of sampling frame (contact rate cr) and characterizing willingness of sample members to participate (enrolment rate er). The mean quality score for the sampling frames was 92% for PR, 87% for HR and 85% for ER; they contributed on average 23, 20, and 26% to the respective non-response rates. For all frame types and both sexes the lowest quality score occurred in the age group 35 - 44, suggesting a reduced ability to track migration of a highly mobile population group. The patterns in the age/sex distribution of er indicate at least for males in PR and females in HR a potential for non-response bias. Estimation of non-response bias through an abbreviated questionnaire failed because of low item response. We found that contact rate characterizes sampling frame quality. For all frame types it had a major influence on response rate. It is likely that low er and low cr cause different kind of bias, requiring different measures to minimize their effects.