A Combined Computational and Experimental Approach to Studying Tropomyosin Kinase Receptor B Binders for Potential Treatment of Neurodegenerative Diseases.

Tropomyosin kinase receptor B (TrkB) has been explored as a therapeutic target for neurological and psychiatric disorders. However, the development of TrkB agonists was hindered by our poor understanding of the TrkB agonist binding location and affinity (both affect the regulation of disorder types). This motivated us to develop a combined computational and experimental approach to study TrkB binders. First, we developed a docking method to simulate the binding affinity of TrkB and binders identified by our magnetic drug screening platform from Gotu kola extracts. The Fred Docking scores from the docking computation showed strong agreement with the experimental results. Subsequently, using this screening platform, we identified a list of compounds from the NIH clinical collection library and applied the same docking studies. From the Fred Docking scores, we selected two compounds for TrkB activation tests. Interestingly, the ability of the compounds to increase dendritic arborization in hippocampal neurons matched well with the computational results. Finally, we performed a detailed binding analysis of the top candidates and compared them with the best-characterized TrkB agonist, 7,8-dyhydroxyflavon. The screening platform directly identifies TrkB binders, and the computational approach allows for the quick selection of top candidates with potential biological activities based on the docking scores.

Extracellular signal-regulated kinase regulates microglial immune responses in Alzheimer's disease.

The importance of mitogen-activated protein kinase (MAPK) pathway signaling in regulating microglia-mediated neuroinflammation in Alzheimer's disease (AD) remains unclear. We examined the role of MAPK signaling in microglia using a preclinical model of AD pathology and quantitative proteomics studies of postmortem human brains. In multiplex immunoassay analyses of MAPK phosphoproteins in acutely isolated microglia and brain tissue from 5xFAD mice, we found phosphorylated extracellular signal-regulated kinase (ERK) was the most strongly upregulated phosphoprotein within the MAPK pathway in acutely isolated microglia, but not whole-brain tissue from 5xFAD mice. The importance of ERK signaling in primary microglia cultures was next investigated using transcriptomic profiling and functional assays of amyloid-ß and neuronal phagocytosis, which confirmed that ERK is a critical regulator of IFNγ-mediated pro-inflammatory activation of microglia, although it was also partly important for constitutive microglial functions. Phospho-ERK was an upstream regulator of disease-associated microglial gene expression (Trem2, Tyrobp), as well as several human AD risk genes (Bin1, Cd33, Trem2, Cnn2), indicative of the importance of microglial ERK signaling in AD pathology. Quantitative proteomic analyses of postmortem human brain showed that ERK1 and ERK2 were the only MAPK proteins with increased protein expression and positive associations with neuropathological grade. In a human brain phosphoproteomic study, we found evidence for increased flux through the ERK signaling pathway in AD. Overall, our analyses strongly suggest that ERK phosphorylation, particularly in microglia in mouse models, is a regulator of pro-inflammatory immune responses in AD pathogenesis.

The impact of surface area, volume, curvature, and Lennard-Jones potential to solvation modeling.

This article explores the impact of surface area, volume, curvature, and Lennard-Jones (LJ) potential on solvation free energy predictions. Rigidity surfaces are utilized to generate robust analytical expressions for maximum, minimum, mean, and Gaussian curvatures of solvent-solute interfaces, and define a generalized Poisson-Boltzmann (GPB) equation with a smooth dielectric profile. Extensive correlation analysis is performed to examine the linear dependence of surface area, surface enclosed volume, maximum curvature, minimum curvature, mean curvature, and Gaussian curvature for solvation modeling. It is found that surface area and surfaces enclosed volumes are highly correlated to each other's, and poorly correlated to various curvatures for six test sets of molecules. Different curvatures are weakly correlated to each other for six test sets of molecules, but are strongly correlated to each other within each test set of molecules. Based on correlation analysis, we construct twenty six nontrivial nonpolar solvation models. Our numerical results reveal that the LJ potential plays a vital role in nonpolar solvation modeling, especially for molecules involving strong van der Waals interactions. It is found that curvatures are at least as important as surface area or surface enclosed volume in nonpolar solvation modeling. In conjugation with the GPB model, various curvature-based nonpolar solvation models are shown to offer some of the best solvation free energy predictions for a wide range of test sets. For example, root mean square errors from a model constituting surface area, volume, mean curvature, and LJ potential are less than 0.42 kcal/mol for all test sets. © 2016 Wiley Periodicals, Inc.

Accurate, robust, and reliable calculations of Poisson-Boltzmann binding energies.

Poisson-Boltzmann (PB) model is one of the most popular implicit solvent models in biophysical modeling and computation. The ability of providing accurate and reliable PB estimation of electrostatic solvation free energy, ΔGel, and binding free energy, ΔΔGel, is important to computational biophysics and biochemistry. In this work, we investigate the grid dependence of our PB solver (MIBPB) with solvent excluded surfaces for estimating both electrostatic solvation free energies and electrostatic binding free energies. It is found that the relative absolute error of ΔGel obtained at the grid spacing of 1.0 Å compared to ΔGel at 0.2 Å averaged over 153 molecules is less than 0.2%. Our results indicate that the use of grid spacing 0.6 Å ensures accuracy and reliability in ΔΔGel calculation. In fact, the grid spacing of 1.1 Å appears to deliver adequate accuracy for high throughput screening. © 2017 Wiley Periodicals, Inc.

Local Effects on Airway Inflammation and Systemic Uptake of 5 nm PEGylated and Citrated Gold Nanoparticles in Asthmatic Mice.

Nanotechnology is showing promise in many medical applications such as drug delivery and hyperthermia. Nanoparticles administered to the respiratory tract cause local reactions and cross the blood-air barrier, thereby providing a means for easy systemic administration but also a potential source of toxicity. Little is known about how these effects are influenced by preexisting airway diseases such as asthma. Here, BALB/c mice are treated according to the ovalbumin (OVA) asthma protocol to promote allergic airway inflammation. Dispersions of polyethylene-glycol-coated (PEGylated) and citrate/tannic-acid-coated (citrated) 5 nm gold nanoparticles are applied intranasally to asthma and control groups, and (i) airway resistance and (ii) local tissue effects are measured as primary endpoints. Further, nanoparticle uptake into extrapulmonary organs is quantified by inductively coupled plasma mass spectrometry. The asthmatic precondition increases nanoparticle uptake. Moreover, systemic uptake is higher for PEGylated gold nanoparticles compared to citrated nanoparticles. Nanoparticles inhibit both inflammatory infiltrates and airway hyperreactivity, especially citrated gold nanoparticles. Although the antiinflammatory effects of gold nanoparticles might be of therapeutic benefit, systemic uptake and consequent adverse effects must be considered when designing and testing nanoparticle-based asthma therapies.

Rigidity Strengthening: A Mechanism for Protein-Ligand Binding.

Protein-ligand binding is essential to almost all life processes. The understanding of protein-ligand interactions is fundamentally important to rational drug and protein design. Based on large scale data sets, we show that protein rigidity strengthening or flexibility reduction is a mechanism in protein-ligand binding. Our approach based solely on rigidity is able to unveil a surprisingly apparently long-range contribution of apparently four residue layers to protein-ligand binding, which has ramifications for drug and protein design. Additionally, the present work reveals that among various pairwise interactions, the short-range ones within the distance of the van der Waals diameter are most important. It is found that the present approach outperforms all other state-of-the-art scoring functions for protein-ligand binding affinity predictions of two benchmark test sets.

Tollip, an early regulator of the acute inflammatory response in the substantia nigra.

BACKGROUND: Tollip is a ubiquitously expressed protein, originally described as a modulator of the IL-1R/TLR-NF-κB signaling pathways. Although this property has been well characterized in peripheral cells, and despite some evidence of its expression in the central nervous system, the role of Tollip in neuroinflammation remains poorly understood. The present study sought to explore the implication of Tollip in inflammation in the substantia nigra pars compacta, the structure affected in Parkinson's disease. METHODS: We first investigated Tollip distribution in the midbrain by immunohistochemistry. Then, we addressed TLR4-mediated response by intra-nigral injections of lipopolysaccharide (LPS), a TLR4 agonist, on inflammatory markers in Tollip knockout (KO) and wild-type (WT) mice. RESULTS: We report an unexpectedly high Tollip immunostaining in dopaminergic neurons of the mice brain. Second, intra-nigral injection of LPS led to increased susceptibility to neuroinflammation in Tollip KO compared to Tollip WT mice. This was demonstrated by a significant increase of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1ß), interleukin 6 (IL-6), and interferon gamma (IFN-γ) messenger RNA (mRNA) in the midbrain of Tollip KO mice upon LPS injection. Consistently, brain rAAV viral vector transduction with a nuclear factor kappa B (NF-κB)-inducible reporter gene confirmed increased NF-κB activation in Tollip KO mice. Lastly, Tollip KO mice displayed higher inducible NO synthase (iNOS) production, both at the messenger and protein level when compared to LPS-injected WT mice. Tollip deletion also aggravated LPS-induced oxidative and nitrosative damages, as indicated by an increase of 8-oxo-2'-deoxyguanosine and nitrotyrosine immunostaining, respectively. CONCLUSIONS: Altogether, these findings highlight a critical role of Tollip in the early phase of TLR4-mediated neuroinflammation. As brain inflammation is known to contribute to Parkinson's disease, Tollip may be a potential target for neuroprotection.

Defective macrophage migration in Gαi2- but not Gαi3-deficient mice.

Various heterotrimeric G(i) proteins are considered to be involved in cell migration and effector function of immune cells. The underlying mechanisms, how they control the activation of myeloid effector cells, are not well understood. To elucidate isoform-redundant and -specific roles for Gα(i) proteins in these processes, we analyzed mice genetically deficient in Gα(i2) or Gα(i3). First, we show an altered distribution of tissue macrophages and blood monocytes in the absence of Gα(i2) but not Gα(i3). Gα(i2)-deficient but not wild-type or Gα(i3)-deficient mice exhibited reduced recruitment of macrophages in experimental models of thioglycollate-induced peritonitis and LPS-triggered lung injury. In contrast, genetic ablation of Gα(i2) had no effect on Gα(i)-dependent peritoneal cytokine production in vitro and the phagocytosis-promoting function of the Gα(i)-coupled C5a anaphylatoxin receptor by liver macrophages in vivo. Interestingly, actin rearrangement and CCL2- and C5a anaphylatoxin receptor-induced chemotaxis but not macrophage CCR2 and C5a anaphylatoxin receptor expression were reduced in the specific absence of Gα(i2). Furthermore, knockdown of Gα(i2) caused decreased cell migration and motility of RAW 264.7 cells, which was rescued by transfection of Gα(i2) but not Gα(i3). These results indicate that Gα(i2), albeit redundant to Gα(i3) in some macrophage activation processes, clearly exhibits a Gα(i) isoform-specific role in the regulation of macrophage migration.

La-doped MIL-88B(Fe)-NH2: a mixed-metal-organic framework photocatalyst for highly efficient reduction of Cr(vi) in an aqueous solution.

With the aim to resolve the problem of water pollution, we herein propose a new photocatalyst based on metal-organic frameworks (MOFs), called La-doped MIL-88B(Fe)-NH2 (MIL-88B((1 - x)Fe/xLa)-NH2), which was designed and employed for the photocatalytic reduction of Cr(vi) in aqueous solutions. MIL-88B((1-x)Fe/xLa)-NH2 materials with different x values were synthesized via a one-pot solvothermal method. Their characteristics were investigated using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET) analysis, Fourier-transform infrared (FT-IR) spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). We found that compared to pristine MIL-88B(Fe)-NH2 with a photocatalytic efficiency of 67.08, MIL-88B((1 - x)Fe/xLa)-NH2 materials with x = 0.010, 0.025 and 0.050 exhibit excellent photocatalytic efficiencies reaching 88.21, 81.19 and 80.26%, respectively, after only 30 minutes of irradiation at a small catalyst dosage of 0.2 g L-1. These La-doped MIL-88B(Fe)-NH2 photocatalysts can work well under mild conditions (pH = 6). Furthermore, they are robust-can be recycled for at least four consecutive runs without any activity loss. This novel material is promising for the photocatalytic degradation of pollutants.

Native-state proteomics of Parvalbumin interneurons identifies unique molecular signatures and vulnerabilities to early Alzheimer's pathology.

Dysfunction in fast-spiking parvalbumin interneurons (PV-INs) may represent an early pathophysiological perturbation in Alzheimer's Disease (AD). Defining early proteomic alterations in PV-INs can provide key biological and translationally-relevant insights. We used cell-type-specific in-vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state PV-IN proteomes. PV-IN proteomic signatures include high metabolic and translational activity, with over-representation of AD-risk and cognitive resilience-related proteins. In bulk proteomes, PV-IN proteins were associated with cognitive decline in humans, and with progressive neuropathology in humans and the 5xFAD mouse model of Aß pathology. PV-IN CIBOP in early stages of Aß pathology revealed signatures of increased mitochondria and metabolism, synaptic and cytoskeletal disruption and decreased mTOR signaling, not apparent in whole-brain proteomes. Furthermore, we demonstrated pre-synaptic defects in PV-to-excitatory neurotransmission, validating our proteomic findings. Overall, in this study we present native-state proteomes of PV-INs, revealing molecular insights into their unique roles in cognitive resiliency and AD pathogenesis.

Morphology of the triangular fibrocartilage complex of the Vietnamese adult: a cadaveric study.

Objective: This descriptive study aims to describe various anatomical morphological indicators of the triangular fibrocartilage complex (TFCC) in Vietnamese adults. Materials and methods: We analyzed 30 wrist joints from 15 fresh cadavers. To access the components of the TFCC, the wrist joints were dissected and measured, and anatomical morphological indices, inclu-ding length, width, thickness, origin, and insertion, were recorded. Results: Nine of 30 articular discs had central tears. The average length of the articular disc was 10.05±2.26 mm, while the average width was 12.10±1.39 mm. The average thickness of the articular disk on the ulnar side was 1.56±0.42 mm, while the average thickness of the articular disk on the radial side was 2.63±1.04 mm. Most meniscus homologues (86.6%) were of the narrow opening type according to the Ishii classification, with a horizontal dimension of 6.98±2.05 mm, anteroposterior diameter of 8.94±2.46 mm, and thickness of 1.27±0.41 mm. The volar radioulnar ligament averaged 12.75±2.17 mm in length and 2.54±0.77 mm in width, while the dorsal radioulnar ligament ave-raged 12.82±2.63 mm in length and 2.37±0.65 mm in width. The ulnar collateral ligament averaged 13.59±2.79 mm in length, 3.75±0.80 mm in width, and 0.95±0.46 mm in thickness. The ulnolunate and ulnotriquetral ligaments had average lengths of 7.34±2.87 mm and 5.70±2.98 mm, widths of 3.93±1.55 mm and 4.87±1.06 mm, and thicknesses of 0.96±0.61 mm and 1.43±0.98 mm, respectively. Conclusions: There are no differences in the shape or structure of the adult Vietnamese TFCC. No significant differences were noted in any TFCC component according to wrist side or gender.

Graphene woven fabric-polydimethylsiloxane piezoresistive films for smart multi-stimuli responses.

The outstanding properties of graphene, including its electromechanical property, could be engineered for wearable electronic sensor platforms. The tubular graphene weaved into a mesh or graphene woven fabrics (GWF) has been reported as one of the most sensitive materials for deformation detection, as well as a promising temperature sensor. Herein, we present the performance of our developed flexible, stretchable, and multiple sensitive sensors fabricated from GWF embedded in polydimethylsiloxane (PDMS) film substrate. The GWF/PDMS sensor shows a pressure sensitivity of 0.0142 kPa-1 in a wide linearity range of 0-20 kPa, an outstanding Gauge factor (GF) of 582 at a strain of 6.2 %, and a very high positive sensitivity of 0.0238 °C-1 in the temperature range of 25-80 °C. A practical application as a high sensitivity air pressure sensor able to measure low pressures (in the range of Pa to kPa) was also demonstrated. This sensor platform having desirable performance characteristics is an excellent candidate for wearable devices in the healthcare sector.

Wastewater treatment using a modified A2O process based on fiber polypropylene media.

The removal rates of organics and nutrients in municipal wastewater were examined using a laboratory-scale Anaerobic/Anoxic/Oxic (A2O) process modified with fiber polypropylene media at different operational conditions. The system demonstrated excellent performance with the removal rates of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorous (TP) ranging from 91% to 98%, from 48% to 63%, and from 56% to 71%, respectively. Our system was superior to those previously reported based on more complex biofilm reactors, particularly from an economic point of view. For our system, a considerable reduction of COD (55%-68%) occurred even in the anaerobic reactor. The removal rates of COD and nutrients exhibited a slight decreasing trend with a higher organic loading rate (OLR) (0.5 to 2.2 kg COD m(-3) day(-1)) or with a shorter hydraulic retention time (HRT). The results may be attributed to the competition between nitrifying and heterotrophic bacteria and/or the insufficient time for biological uptake. It is expected that applying fiber polypropylene media to a conventional A2O process may significantly enhance the treatment efficacy of organics and nutrients as a cost-effective strategy.

Value of lipocalin 2 as a potential biomarker for bacterial meningitis.

OBJECTIVES: Central nervous system (CNS) infections are common causes of morbidity and mortality worldwide. We aimed to discover protein biomarkers that could rapidly and accurately identify the likely cause of the infections, essential for clinical management and improving outcome. METHODS: We applied liquid chromatography tandem mass spectrometry on 45 cerebrospinal fluid (CSF) samples from a cohort of adults with and without CNS infections to discover potential diagnostic biomarkers. We then validated the diagnostic performance of a selected biomarker candidate in an independent cohort of 364 consecutively treated adults with CNS infections admitted to a referral hospital in Vietnam. RESULTS: In the discovery cohort, we identified lipocalin 2 (LCN2) as a potential biomarker of bacterial meningitis (BM) other than tuberculous meningitis. The analysis of the validation cohort showed that LCN2 could discriminate BM from other CNS infections (including tuberculous meningitis, cryptococcal meningitis and virus/antibody-mediated encephalitis), with sensitivity of 0.88 (95% confident interval (CI), 0.77-0.94), specificity of 0.91 (95% CI, 0.88-0.94) and diagnostic odds ratio of 73.8 (95% CI, 31.8-171.4). LCN2 outperformed other CSF markers (leukocytes, glucose, protein and lactate) commonly used in routine care worldwide. The combination of LCN2, CSF leukocytes, glucose, protein and lactate resulted in the highest diagnostic performance for BM (area under the receiver operating characteristics curve, 0.96; 95% CI, 0.93-0.99). Data are available via ProteomeXchange with identifier PXD020510. CONCLUSIONS: LCN2 is a sensitive and specific biomarker for discriminating BM from a broad spectrum of other CNS infections. A prospective study is needed to assess the diagnostic utility of LCN2 in the diagnosis and management of CNS infections.

Endoscope drying/storage cabinet: interest and efficacy.

Inadequate drying of endoscope channels is a possible cause of microbial proliferation during storage. This risk could be reduced by any procedure or process used to dry endoscope channels and control storage conditions. The efficacy of a drying and storage cabinet (Hysis Medical) was tested on three different endoscopes: a colonoscope (Olympus); duodenoscope (Fujinon) and an enteroscope (Pentax), all of which had been artificially contaminated with a suspension of Pseudomonas aeruginosa CIP 103467. Changes to the residual internal contamination level of these endoscopes when stored inside or outside the drying cabinet for 12, 24, 48 or 72 h were compared. When stored in the drying and storage cabinet, microbial contamination levels on endoscopes were lower than the number of bacteria initially introduced and could decrease considerably thereafter. For endoscopes stored outside the drying storage cabinet, microbial numbers were stable or even increased. These data demonstrate the advantages of such endoscope drying/storage cabinets that limit the risk of bacterial proliferation in the internal channels of endoscopes during storage, and which ensure that the disinfection level reached at the end of the reprocessing procedure is maintained.

Comparison of the fixative properties of five disinfectant solutions.

Following a French circular published in 2001, the use of glutaraldehyde for the disinfection of reusable medical devices was abandoned in favour of non-fixative disinfectants such as peracetic-acid-based solutions. Data published regarding the fixative properties of alternative disinfectants remain contradictory. We compared the effect of repetitive treatments of polytetrafluoroethylene (PTFE) tubes, contaminated by a liquid medium inoculated with Pseudomonas aeruginosa, using five different disinfectant solutions: two peracetic acid solutions (with and without an activator), glutaraldehyde, ortho-phthaldehyde and succine dialdehyde. The results confirmed that repeated treatments of a PTFE tube with a 2% glutaraldehyde solution induce an important accumulation and/or fixation of protein, compared to peracetic-acid-based disinfectants, for which the accumulation and/or fixation of proteins remain low and vary from one formulation to another.

Biomimetic Electronic Devices for Measuring Bacterial Membrane Disruption.

Antibiotic discovery has experienced a severe slowdown in terms of discovery of new candidates. In vitro screening methods using phospholipids to model the bacterial membrane provide a route to identify molecules that specifically disrupt bacterial membranes causing cell death. Thanks to the electrically insulating properties of the major component of the cell membrane, phospholipids, electronic devices are highly suitable transducers of membrane disruption. The organic electrochemical transistor (OECT) is a highly sensitive ion-to-electron converter. Here, the OECT is used as a transducer of the permeability of a lipid monolayer (ML) at a liquid:liquid interface, designed to read out changes in ion flux caused by compounds that interact with, and disrupt, lipid assembly. This concept is illustrated using the well-documented antibiotic Polymixin B and the highly sensitive quantitation of permeability of the lipid ML induced by two novel recently described antibacterial amine-based oligothioetheramides is shown, highlighting molecular scale differences in their disruption capabilities. It is anticipated that this platform has the potential to play a role in front-line antimicrobial compound design and characterization thanks to the compatibility of semiconductor microfabrication technology with high-throughput readouts.

Design of Multimodal Small Molecules Targeting miRNAs Biogenesis: Synthesis and In Vitro Evaluation.

microRNAs (miRNAs) are emerging as novel biological targets for medicinal chemists to develop chemical tools for intracellular regulation. In this context, the discovery of small-molecule drugs targeting specific miRNAs and modulating their production or function represents a very promising approach that could be further developed for targeted therapy in miRNA-related pathologies. Here, we describe the design of multimodal small molecules as RNA ligands targeting DICER-mediated miRNA maturation. The synthesis and the biochemical evaluation as ligands of stem-loop-structured precursor microRNAs (pre-miRNAs) are reported.

Localization of the 5-hydroxytryptamine2C receptor protein in human and rat brain using specific antisera.

The mouse 5-HT2C receptor and its third and fourth (C-terminal) cytoplasmic domain have been expressed as fusion proteins in bacteria. After purification antisera were generated against the fusion proteins. Characterization by immunoblotting using eukaryotic cells expressing the 5-HT2C and 5-HT2A receptors showed that high titer antibodies could be obtained only against the third and fourth cytoplasmic domain but not the entire receptor. Affinity purified antibodies were used to study the location of 5-HT2C receptors in rat and human brain sections. This distribution was compared with the location of 5-HT2C receptor binding sites as determined by [3H]mesulergine, a 5-HT2C receptor radioligand. The antibodies recognized sites in the rat choroid plexus, hippocampus, cerebral cortex, striatum and substantia nigra with a similar distribution as the 5-HT2C binding sites. One antiserum directed against the 5-HT2C receptor C-terminus crossreacted with the human receptor protein in immunoblots. In human brain sections it labelled sites including cerebral cortex, substantia nigra and cerebellum. Our results demonstrate that the antibodies are suitable to identify 5-TH2C receptors in rat and human brain. They visualize a protein distribution which correlates well with the location of the 5-HT2C receptor binding sites as would be expected if affinity states do not influence the binding pattern.

Embryonic and postnatal mRNA distribution of five somatostatin receptor subtypes in the rat brain.

The messenger RNA (mRNA) expression of somatostatin (SRIF) receptors SSTR-1, SSTR-2, SSTR-3, SSTR-4 and SSTR-5 (called sst1-5, now) was studied in rat brain between embryonic day 17 (E17) and post-natal day 5 (P5) by in situ hybridization histochemistry and compared to that of adult rats. sst1 receptor mRNA expression was very low and restricted at E17, spread out at E18, to reach very high levels comparable to that of adult at P5 (e.g. in temia tecta, posteromedial cortical amygdaloid nucleus, subiculum). At E17/E18, sst2 receptor mRNA expression was low and limited (telencephalon); significant levels were present at P5 in allocortex, hippocampus, locus coeruleus, similarly to adult brain. sst3 receptor mRNA was high at E17 in most brain regions, and almost as ubiquitous as in adult brain at P5. sst4 receptor mRNA was apparently absent at E17, with low levels in the hippocampus, amygdala and habenula at E18; a wider distribution, especially in the hippocampus and cerebral cortex was observed at P5, similar to that of adult. sst5 receptor mRNA was not detected at E17 and negligible at E18; low levels were found in the cortex, hippocampus and cerebellum at P5. However, in adult brain, only the cerebellum and hind-brain showed some sst5 receptor mRNA transcripts. The presence and distribution of SRIF receptor mRNAs differs substantially in embryo and adult brain. Some mRNAs are present throughout development, while others proceed only postnatally to the adult form. There are striking differences within and between the different SRIF receptor mRNAs, suggesting a role in neurogenesis for some SRIF receptors (e.g. sst2). However, mRNA and protein levels do not necessarily correlate.