Crystallizing covalent organic frameworks from metal organic framework through chemical induced-phase engineering

The ordered porous frameworks like MOFs and COFs are generally constructed using the monomers through distinctive metal-coordinated and covalent linkages. Meanwhile, the inter-structural transition between each class of these porous materials is an under-explored research area. However, such altered frameworks are expected to have exciting features compared to their pristine versions. Herein, we have demonstrated a chemical-induction phase-engineering strategy to transform a two-dimensional conjugated Cu-based SA-MOF (Cu-Tp) into 2D-COFs (Cu-TpCOFs). The structural phase transition offered in-situ pore size engineering from 1.1 nm to 1.5-2.0 nm. Moreover, the Cu-TpCOFs showed uniform and low percentage-doped (~ 1-1.5%) metal distribution and improved crystallinity, porosity, and stability compared to the parent Cu-Tp MOF. The construction of a framework from another framework with new linkages opens interesting opportunities for phase-engineering.

Enzyme-immobilized hierarchically porous covalent organic framework biocomposite for catalytic degradation of broad-range emerging pollutants in water

Efficient enzyme immobilization is crucial for the successful commercialization of large-scale enzymatic water treatment. However, issues such as lack of high enzyme loading coupled with enzyme leaching present challenges for the widespread adoption of immobilized enzyme systems. The present study describes the development and bioremediation application of an enzyme biocomposite employing a cationic macrocycle-based covalent organic framework (COF) with hierarchical porosity for the immobilization of horseradish peroxidase (HRP). The intrinsic hierarchical porous features of the azacalix[4]arene-based COF (ACA-COF) allowed for a maximum HRP loading capacity of 0.76 mg/mg COF with low enzyme leaching (<5.0 %). The biocomposite, HRP@ACA-COF, exhibited exceptional thermal stability (∼200 % higher relative activity than the free enzyme), and maintained ∼60 % enzyme activity after five cycles. LCMSMS analyses confirmed that the HRP@ACA-COF system was able to achieve > 99 % degradation of seven diverse types of emerging pollutants (2-mercaptobenzothiazole, paracetamol, caffeic acid, methylparaben, furosemide, sulfamethoxazole, and salicylic acid)in under an hour. The described enzyme-COF system offers promise for efficient wastewater bioremediation applications.

Chemically Gradient Hydrogen-Bonded Organic Framework Crystal Film

Hydrogen-bonded organic frameworks (HOFs) are ordered supramolecular solid structures, however, nothing much explored as centimeter-scale self-standing films. The fabrication of such crystals comprising self-supported films is challenging due to the limited flexibility and interaction of the crystals, and therefore studies on 2D macrostructures of HOFs are limited to external supports. Herein, we introduce a novel chemical gradient strategy to fabricate a crystal-deposited HOF film on an in-situ-formed COP-film (Tam-Bdca-CGHOF). The fabricated film showed versatility in chemical bonding along its thickness from covalent to hydrogen-bonded network. The kinetic-controlled Tam-Bdca-CGHOF showed enhanced proton conductivity (0.83 µS cm-1) compared to its rapid kinetic analogue, Tam-Bdca-COP (0.21 µS cm-1), which signifies the advantage of bonding-engineering in the same system.

Association between antithyroid peroxidase antibody and recurrent miscarriage

OBJECTIVE

Thyroid disease is the second most commonly affected disease in childbearing women, after diabetes, and thyroid autoimmunity in pregnancy has been connected with adverse pregnancy outcomes such as miscarriage, recurrent miscarriage, preterm birth, and low IQ. The study seeks to determine the correlation between anti-thyroid peroxidase antibodies and unexplained recurrent miscarriage.

PATIENTS AND METHODS

124 women were included in this case-control study, divided into 62 women who have experienced unexplained recurrent miscarriages and 62 healthy women without a history of miscarriage. Screening for TSH and anti-TPO antibody were done for both groups.

RESULTS

The prevalence rate of positive anti-TPO antibody in women with recurrent miscarriage was 19.4%, while in women without miscarriage was 6.5% (which is considerably higher in cases than in women without recurrent miscarriage with a p-value of 0.03 and an odd ratio of 3.48 (95% CI; 1.06-11.48).

CONCLUSIONS

A statistically significant relationship between anti-TPO antibodies and recurrent miscarriage has been detected. We recommend screening for TSH and thyroid antibodies for women with recurrent miscarriages and further studies on the effect of levothyroxine therapy for euthyroid women with antibody positive.

Salicylaldehydate coordinated two-dimensional-conjugated metal-organic frameworks

A novel class of copper-based 2D-c-MOF was synthesized from 1,3,5-triformylphloroglucinol using green mechano-chemistry. Herein, metal coordination with the salicylaldehyde functional moiety was explored for the first time in MOFs. Moreover, an intrinsic semiconductive copper-based SA-MOF thin film was fabricated using an in situ salt-free method at room temperature.

Covalent Organic Framework Based on Azacalix[4]arene for the Efficient Capture of Dialysis Waste Products

Azacalix[n]arenes (ACAs) are lesser-known cousins of calix[n]arenes that contain amine bridges instead of methylene bridges, so they generally have higher flexibility due to enlarged cavities. Herein, we report a highly substituted cationic azacalix[4]arene-based covalent organic framework (ACA-COF) synthesized by the Zincke reaction under microwave irradiation. The current work is a rare example of a synthetic strategy that utilizes the chemical functionalization of an organic macrocycle to constrain its conformational flexibility and, thereby, produce an ordered material. Considering the ACA cavity dimensions, and the density and diversity of the polar groups in ACA-COF, we used it for adsorption of uric acid and creatinine, two major waste products generated during hemodialysis treatment in patients with renal failure. This type of application, which has the potential to save ∼400 L of water per patient per week, has only been recognized in the last decade, but could effectively address the problem of water scarcity in arid areas of the world. Rapid adsorption rates (up to k = 2191 g mg^-1 min^-1) were observed in our COF, exceeding reported values by several orders of magnitude.

Polythiacalixarene-Embedded Gold Nanoparticles for Visible-Light-Driven Photocatalytic CO2 Reduction

Metal nanoparticles are potent reaction catalysts, but they tend to aggregate, thereby limiting their catalytic efficiency. Their coordination with specific functional groups within a porous structure prevents their aggregation and facilitates the mass flow of catalytic starting materials and products. Herein, we use a thiacalix[4]arene-based polymer as a porous support with abundant docking sites for Au nanoparticles. The sulfur atoms bridging the phenolic subunits of thiacalix[4]arene serve as Lewis basic sites that coordinate Au atoms. Therefore, this approach takes advantage of the functional groups inherent in the monomer and avoids laborious postsynthetic modifications of the polymer. The presented system was tested for visible-light-driven photocatalytic CO₂ reduction, where it showed adequate ability to generate 6.74 μmol g^-1 CO over the course of 4 h, while producing small amounts of the CH₄ product. This study aims to stimulate interest in the design and development of synthetically simpler porous polymer supports for various metal nanoparticles in catalytic and other applications.

Solvent‐Influenced Fragmentations in Free‐Standing Three‐Dimensional Covalent Organic Framework Membranes for Hydrophobicity Switching

The ordered open organic frameworks membranes are attractive candidates for flow‐assisted molecular separations. The physicochemical properties of such membranes mostly depend on their selectively chosen functional building blocks. In this work, we have introduced a novel concept of functional switchability of three‐dimensional covalent organic framework (3D‐COF) membranes through a simple solvent‐influenced fragmentation method. This room‐temperature interfacial synthesis provides free‐standing 3D‐COF membranes with distinct physicochemical properties from the same building monomers. Notably, the change of solvent from chloroform to ethyl acetate switches the membrane property from hydrophilic (water contact angle 60°) to hydrophobic (water contact angle 142°) nature. The hydrophobic 3D‐COF membrane selectively passes oil molecules from an oil–water emulsion with a gravitational flux of 1536 L m⁻² h⁻¹.

Metallated Isoindigo-Porphyrin Covalent Organic Framework Photocatalyst with a Narrow Band Gap for Efficient CO2 Conversion

Photocatalytic CO₂ reduction into formate (HCOO^-) has been widely studied with semiconductor and molecule-based systems, but it is rarely investigated with covalent organic frameworks (COFs). Herein, we report a novel donor-acceptor COF named Co-PI-COF composed of isoindigo and metallated porphyrin subunits that exhibits high catalytic efficiency (∼50 μmol formate g^-1 h^-1) at low-power visible-light irradiation and in the absence of rare metal cocatalysts. Density functional theory calculations and experimental diffuse-reflectance measurements are used to explain the origin of catalytic efficiency and the particularly low band gap (0.56 eV) in this material. The mechanism of photocatalysis is also studied experimentally and is found to involve electron transfer from the sacrificial agent to the excited Co-PI-COF. The observed high-efficiency conversion could be ascribed to the enhanced CO₂ adsorption on the coordinatively unsaturated cobalt centers, the narrow band gap, and the efficient transfer of the charge originating from the postsynthetic metallation. It is anticipated that this study will pave the way toward the design of new simple and efficient catalysts for photocatalytic CO₂ reduction into useful products.

A critical review on geosmin and 2-methylisoborneol in water: sources, effects, detection, and removal techniques

The exposure to geosmin (GSM) and 2-methylisoborneol (2-MIB) in water has caused a negative impact on product reputation and customer distrust. The occurrence of these compounds and their metabolites during drinking water treatment processes has caused different health challenges. Conventional treatment techniques such as coagulation, sedimentation, filtration, and chlorination employed in removing these two commonest taste and odor compounds (GSM and 2-MIB) were found to be ineffective and inherent shortcomings. The removal of GSM and MIB were found to be effective using combination of activated carbon and ozonation; however, high treatment cost associated with ozonation technique and poor regeneration efficiency of activated carbon constitute serious setback to the combined system. Other shortcoming of the activated carbon adsorption and ozonation include low adsorption efficiency due to the presence of natural organic matter and humic acid. In light of this background, the review is focused on the sources, effects, environmental pathways, detection, and removal techniques of 2-MIB and GSM from aqueous media. Although advanced oxidation processes (AOPs) were found to be promising to remove the two compounds from water but accompanied with different challenges. Herein, to fill the knowledge gap analysis on these algal metabolites (GSM and 2-MIB), the integration of treatment processes vis-a-viz combination of one or more AOPs with other conventional methods are considered logical to remove these odorous compounds and hence could improve overall water quality.

Potential of using kaolin as a natural adsorbent for the removal of pollutants from tannery wastewater

In the present work, kaolin sample from Gbako Local Government, Niger State, Nigeria was used as an adsorbent for the removal chloride, COD, BOD, sulphate, chromium, cadmium, zinc and the reduction of total alkalinity in tannery wastewater. The kaolin sample was pretreated to enhance its adsorption capacity and then characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), High Resolution Electron Microscopy (HRSEM), High Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive Spectroscopy (EDX), Selective Area Electron Diffraction (SAED) and Brunauer Emmett-Teller (BET). The specific surface area, pore volume and pore diameter of the kaolin were 17 m²/g, 0.018 cm³/g and 3.587 nm, respectively. The adsorption methods of the parameters onto the kaolin were investigated as functions of contact time, adsorbent dosage and temperature. Equilibrium isotherms for the adsorption parameters were carried out experimentally and the adsorption data correlated very well with Jovanovic and Redlich-Peterson models. Furthermore, the adsorption kinetics followed the Avrami model. From the results of the study it was established that kaolin from Gbako, Nigeria can serve as an economic, safe and effective natural adsorbent for the pollutants removal from tannery wastewater.

Weak Intermolecular Interactions in Covalent Organic Framework-Carbon Nanofiber Based Crystalline yet Flexible Devices

The redox-active and porous structural backbone of covalent organic frameworks (COFs) can facilitate high-performance electrochemical energy storage devices. However, the utilities of such 2D materials as supercapacitor electrodes in advanced self-charging power-pack systems have been obstructed due to the poor electrical conductivity and subsequent indigent performance. Herein, we report an effective strategy to enhance the electrical conductivity of COF thin sheets through the in situ solid-state inclusion of carbon nanofibers (CNF) into the COF precursor matrix. The obtained COF-CNF hybrids possess a significant intermolecular π···π interaction between COF and the graphene layers of the CNF. As a result, these COF-CNF hybrids (DqTp-CNF and DqDaTp-CNF) exhibit good electrical conductivity (0.25 × 10^-3 S cm^-1), as well as high performance in electrochemical energy storage (DqTp-CNF: 464 mF cm^-2 at 0.25 mA cm^-2). Also, the fabricated, mechanically strong quasi-solid-state supercapacitor (DqDaTp-CNF SC) delivered an ultrahigh device capacitance of 167 mF cm^-2 at 0.5 mA cm^-2. Furthermore, we integrated a monolithic photovoltaic self-charging power pack by assembling DqDaTp-CNF SC with a perovskite solar cell. The fabricated self-charging power pack delivered excellent performance in the areal capacitance (42 mF cm^-2) at 0.25 mA cm^-2 after photocharging for 300 s.

Influence of place learning on somatostatin levels in the rat brain following environmental deprivation

We have previously reported increased somatostatin levels in the cerebral cortex of rats housed in impoverished environment and subsequently subjected to a behavioural testing procedure, consisting of open-field exposure and spatial learning. The aim of the present study was to evaluate the degree of neurochemical specificity of the activation of somatostatin neurotransmission and to examine whether the altered levels were due to learning stimulation. Adult rats, previously housed individually for 30 days, were exposed to repeated sessions of a spatial learning task (2 days or 14 days) or repeated sessions of free swimming (14 days). The training sessions of the 14 day group consisted in recurrently changed position of the platform in a learning-set paradigm. Our data showed increased somatostatin immunoreactivity, and unchanged substance P immunoreactivity in the posterior part of the cerebral cortex. However, somatostatin levels increased to a similar extent following 14 days of repeated spatial learning sessions as free swimming sessions. We conclude that the activity of the cortical somatostatin system appears to be sensitive to environmentally induced sensorimotor stimulation in general, rather than learning per se. Thus, external stimulation of early clinical dementia patients with preserved sensorimotor receptivity, in an attempt to restore cognitive function, might be associated with altered somatostatin levels.

Transcription factor AP-2 gene expression in adult rat hippocampal regions: effects of environmental manipulations

Environmental enrichment increases glucocorticoid receptor expression in hippocampal pyramidal neurons, but the molecular mechanisms are unknown. Several transcription factors are expressed in hippocampal neurons where they respond to environmental stimuli. In this study 12 adult male rats (n = 6 in each group) were exposed to enriched or isolated environment for 30 days. The expression of AP-2 mRNA, studied by in situ hybridization, was attenuated by environmental enrichment in the CA2 and CA3 subfields of the hippocampus. AP-2 may be involved in the environmental effect of glucocorticoid receptor gene expression in these neurons.

Environmental influence on somatostatin levels and gene expression in the rat brain

In the present study we have quantified preprosomatostatin-mRNA and somatostatin levels in rat brain following environmental stimulation. Animals were housed for 30 days in an enriched or impoverished environment prior to analysis. After 30 days of housing half of the rats from each environment were behaviourally tested for 3 days. Housing in enriched environment improved performance in a spatial learning situation. The open-field behaviour of these animals was characterized by initially higher rearing scores and a more rapid habituation to novel environment as measured by spontaneous locomotor activity. We found significantly elevated somatostatin levels in the cortex following enriched environment, compared with impoverished environment. Exposure to behavioural testing of impoverished animals led to increased cortical somatostatin levels. Hypothalamic somatostatin levels increased significantly after housing in enriched environment, while the testing procedure had no influence. Our data shows that the somatostatin system in the rat brain was activated in association with cognitive changes, that were induced by housing in an enriched environment.

Immunohistochemical and behaviour pharmacological analysis of rats inoculated intranasally with vesicular stomatitis virus

A temperature-sensitive mutant of vesicular stomatitis virus was inoculated intranasally into infant Sprague-Dawley rats aged 9 to 17 days. Rats receiving the virus at 9 days of age had an extensive spread of infection throughout the brain and the animals died after a few days. Rats inoculated at day 11 postnatally survived and the infection was limited to the olfactory pathways, hypothalamus, diagonal bands and the anterior raphe nuclei. Stereological measurements showed that the volume of infected neurons constituted 67 +/- 10% of the total neuronal volume in the dorsal raphe nucleus. Double-labelling experiments revealed that both 5-hydroxytryptamine- and substance P-immunoreactive neurons contained the virus antigen. The motor stimulant effect of amphetamine was studied at 3 months post infection. The increase in amphetamine-induced frequency and duration of rearing was significantly attenuated in infected rats and the amphetamine-induced locomotion was slightly reduced.

Increased expression of brain-derived neurotrophic factor mRNA in rat hippocampus is associated with improved spatial memory and enriched environment

Enriched environment has been shown to enhance learning and memory and to induce morphological changes in the hippocampus. We report that rats housed in an enriched environment showed improved performance in the Morris water maze and decreased spontaneous motor activity. Exposure to behavioural tests increased expression of the mRNA that encodes brain-derived neurotrophic factor in the hippocampus. This was not seen when rats subjected to impoverished housing were tested suggesting that environmental history of the animal is of importance to induce expression of brain-derived neurotrophic factor in the hippocampus that may promote neuronal changes related to learning and memory.

Persistent changes in behaviour and brain serotonin during ageing in rats subjected to infant nasal virus infection

Suckling rats were infected intranasally with the temperature-sensitive mutant G41 strain of vesicular stomatitis virus. The rats survived but demonstrated lifelong learning deficits in the Morris maze and impaired exploratory behaviour in the open field test. When examined at 18 months of age they had a severe loss of neurons in the medial and dorsal raphe nuclei in the brain stem and reduced levels of serotonin and its metabolite 5-hydroxyindole acetic acid in the cerebral neocortex and hippocampus. The levels of noradrenaline, dopamine, homovanillic acid, 3,4-dihydroxyphenylacetic acid, choline acetyltransferase and glutamate decarboxylase were largely unaffected. The permanent disturbance in brain serotonin metabolism did not cause any histological changes in the cerebral cortex. Thus there were no neurofibrillary tangles or amyloid plaques as has been reported as a late effect of chemically induced lesion to the cholinergic system in the rat brain. It is concluded that the brain serotonergic system is especially vulnerable to an episode of virus attack along olfactory pathways and that the neurochemical and behavioural alterations caused by such an episode persist during a major part of the animal's life span.

Learning deficits in aged rats pretreated chronically with barbital and tested late in abstinence: alleviation by tetrahydroaminoacridine

Physostigmine and tetrahydroaminoacridine (THA) have been reported to improve cognitive function in patients with Alzheimer's disease. Two experiments were conducted to examine the effects of these anticholinesterase agents on learning in aged rats pretreated chronically with barbital. In the first experiment animals received barbital in their drinking water for 46 weeks. Controls were given only water. On days 100-104 of abstinence, when the animals were 20 months old, acquisition of the Morris maze task was initiated after treatment with physostigmine. It was found that physostigmine improved learning of the maze task in control but not barbital treated rats. In the second experiment animals received barbital solution or water as in experiment one. On days 100-103 of abstinence they were injected with THA before being tested in the Morris water maze. It was found that THA improved learning in both barbital treated and control rats. These results corroborate clinical findings of improved cognitive function following treatment with THA, and suggest that the therapeutic effects of THA may be mediated by mechanisms distinct from cholinesterase inhibition. Furthermore chronic barbital treatment could be used as a model to study cognitive disturbances in experimental animals.

Environmental influence on behaviour and nerve growth factor in the brain

The influence of the environment on the endogenous levels of nerve growth factor (NGF) in the cortex, hippocampus and septum was examined in adult (82 days old) and juvenile (51 days old) rats. Animals were reared/housed for 30 days in an enriched, standard or isolated environment prior to analysis. In addition, another group of rats were given behavioural tests (4 days) after differential rearing/housing before measurements of NGF. We found complex variations in the level of NGF both in juvenile and adult hippocampus after differential environmental rearing/housing. Rearing/housing in an enriched environment improved performance in the Morris maze and decreased spontaneous motor activity. Exposure to behavioural tests caused alterations in adult hippocampus and septum NGF levels. The results show that testing in a novel environment causes small but significant changes in the hippocampal and septal NGF levels depending upon the environmental history of the animal. In view of the purported involvement of the septohippocampal pathway and NGF in the pathophysiology of Alzheimer's disease, our finding suggests that lack of adequate environmental stimulation might be of importance in age-related behavioural and neurochemical deficits.

Multiple effects of tetrahydroaminoacridine on the cholinergic system: biochemical and behavioural aspects

9-Amino-1,2,3,4-tetrahydroaminoacridine (THA) in combination with lecithin has been reported to improve the memory of Alzheimer's disease patients. We have examined some properties of THA in vitro and in vivo so as to define some of the mechanism(s) by which THA might produce its therapeutic effects. In vitro, THA was more potent at inhibiting human plasma cholinesterase (IC50 = 0.03 microM) than human erythrocyte acetylcholinesterase (IC50 = 0.3 microM) and rat brain acetylcholinesterase (IC50 = 0.32 microM). Radioligand binding studies indicated that THA binds reversibly and competitively to primary M1 and M2 human cortical muscarinic receptors with similar affinities. Moreover, THA showed similar affinity for temporal cortices muscarinic receptors from Alzheimer and non-Alzheimer (control) brains. In vivo, subcutaneous administration of THA (1-8 mg/kg body weight) to adult rats (6 months old) produced a dose dependent decrease in general activity compared to saline-treated rats. However, at a concentration of 0.5 mg/kg body weight, the general activity of the rats was increased compared to saline-treated rats. The cognitive function of the THA-treated adult rats (subcutaneously 2 mg/kg body weight) was not significantly improved compared to saline-treated rats. It is concluded that the mechanisms of action of THA on the cholinergic system involve reversible inhibition of cholinesterases and reversible and competitive interaction with muscarinic acetylcholine receptors. These effects might be of therapeutic value in the treatment of Alzheimer's disease.

Behavioural deficits and serotonin depletion in adult rats after transient infant nasal viral infection

Dysfunction of subcortical serotoninergic neurons has been implicated in some behaviour disturbances. The serotoninergic neurons in the dorsal and median raphe project widely in the brain. They innervate the olfactory bulbs and can be targets for exogenous agents attacking the olfactory epithelium and bulbs. We report here an injury to the serotoninergic neurons after intranasal infection in 12-day-old rats with a temperature-sensitive mutant of vesicular stomatitis virus. The brain infection was focal and transient. Viral antigens could no longer be detected 13-15 days after infection. In spite of this the animals, as adults, had a severe serotonin depletion in the cerebral cortex and hippocampus, and showed abnormal locomotor and explorative behaviour as well as learning deficits. The neocortex was histologically intact and parameters related to other neurotransmitters such as dopamine, noradrenaline, GABA and acetylcholine showed no marked changes. A relatively selective damage to serotoninergic nuclei as a result of virus neuroinvasion through a natural portal of entry, may constitute a new pathogenetic mechanism for cortical dysfunction and behavioural deficits.

Adaptive changes in alpha-2 adrenoceptor mediated responses: analgesia, hypothermia and hypoactivity

The acute effects of the alpha-2 adrenoceptor agonists, clonidine and guanfacine, upon antinociception, hypothermia and motor activity were compared under conditions of receptor antagonism, denervation, and chronic administration of a tricyclic antidepressant compound. The analgesic actions of clonidine and guanfacine were antagonised by idazoxan, an alpha-2 receptor antagonist, but potentiated by pretreatment with the noradrenaline neurotoxin DSP4, and attenuated by chronic treatment with desipramine (DMI). Clonidine- and guanfacine-induced hypothermia was antagonised by idazoxan, potentiated by prior treatment with DSP4 and attenuated by chronic administration with DMI. Both clonidine and guanfacine produced decreases in motor activity that were attenuated by idazoxan but unaffected by prior DSP-4 treatment. Chronic DMI administration also attenuated clonidine-induced hypoactivity but potentiated guanfacine-induced hypoactivity. These diverse results describe both similar and differential adaptive mechanisms modulating the functional effect of alpha-2 receptor systems in the central nervous system.

Effects of THA on ionic currents in myelinated axons of Xenopus laevis

In voltage-clamp experiments with the myelinated nerve fibre of Xenopus laevis, 9-amino-1,2,3,4-tetrahydroacridine (THA) decreased both Na+ and K+ currents and shifted the steady state inactivation potential curve in a negative direction. The effects may be described as (a) a decrease of the permeability constant PNa, (b) a modified potential dependence of the inactivating system and (c) a decrease of PK. The Na+ system was affected more than the K+ system.

Effects of the noradrenaline neurotoxin N-2-chloroethyl-N-ethyl-2-bromo-benzylamine hydrochloride (DSP4) on the blood-brain barrier. An experimental study in the mouse using protein tracer and density determination techniques

Cerebral microvessels receive a noradrenergic innervation originating from the locus coeruleus. Previously, many studies have tried to elucidate the role of the central noradrenergic innervation on the blood-brain barrier (BBB). Many of them are based on chemical destruction of the innervation by local injection of 6-hydroxydopamine (6-OHDA) or physical injury to the locus coeruleus. Such methods are not selective and the results reported are contradictory. We have treated mice with a single i.p. injection of the compound, N-2-chloroethyl-N-ethyl-2-bromo-benzylamine hydrochloride (DSP4). This substance induces a selective noradrenaline depletion and, unlike 6-OHDA, it can pass into the brain after an i.p. injection. The animals were allowed to survive for 6 h to 60 days and the BBB was investigated with i.v.-injected horseradish peroxidase (HRP). Brain density values were also determined to find out of edema developed. The light microscopic distribution of HRP in the brain of DSP4-treated animals did not differ from that in control mice, i.e., there were no signs of increased BBB permeability to this protein tracer caused by DSP4. Density determinations revealed statistically significant reduced values in cerebrum (P less than 0.005) and rhombencephalon (cerebellum) (P less than 0.0005) of animals given 100 mg/kg body wt. of DSP4 indicating development of edema. A minor drop in density of the rhombencephalon (cerebellum) (P less than 0.05 at 48 h) and of the cerebrum (statistically not significant) appeared when 50 mg/kg body wt. of DSP4 was injected.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired performance of rats in the Morris swim-maize test late in abstinence following long-term sodium barbital treatment

Rats were tested for place learning in the Morris swim maze on days 110-114 of abstinence following 48 weeks of treatment with sodium barbital. A retarded acquisition of the swim-maze task, that could not be ascribed to motor impairments, was found in the barbital-treated rats. There was a significant difference in brain weight, but there were no significant differences between the control and barbital-treated rats in the frontal cortical concentrations of noradrenaline (NA), dopamine (DA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), nor in the intra- and extrasynaptosomal activities of cerebral cortical monoamine oxidase towards NA and 5-HT. Postsynaptically, neither the cerebral cortical inositol phospholipid breakdown responses to carbachol and NA (mediated by muscarinic and alpha 1-adrenergic receptors, respectively), nor the striatal and cortical densities of muscarinic receptors labelled by [3H]quinuclidinyl benzilate [( 3H]QNB) were found significantly to be altered in the barbital-treated rats. A strong correlation between the density of striatal and cortical [3H]QNB binding sites was seen for the barbital-treated (r = 0.91) but not for the control (r = -0.05) rats. It is suggested that the deficit in performance of the barbital-treated rats in the Morris maze may be related to a cholinergic dysfunction.

Lack of effects of prenatal exposure to lidocaine on development of behavior in rats

The objective of this investigation was to study the effects of lidocaine upon postnatal development of the rat. Lidocaine, 6 mg/kg (21 mumol/kg), was given to a group of 12 rats. Injections were administered intramuscularly, bilaterally in the masseter muscles, once a day on days 10 and 11 of pregnancy. Twelve control rats were given physiologic saline. Clinical signs, mortality, body weight, and food consumption were recorded during pregnancy and lactation. The duration of gestation was also recorded. The development of the offspring was monitored by tests of spontaneous activity, nociception, learning ability, and physical development. No clinical signs of adverse reactions were seen in any of the groups. In the majority of the learning ability tests, the control and lidocaine-treated groups showed similar results. However, in the schedule of differential reinforcement of low rates of responding (DRL 20), the lidocaine-exposed males received more reinforcements than the controls and made fewer responses. In the tests of nociception, a significant difference between sexes was recorded, in that the females were more sensitive than the males in the shock-titration test. Physical development, as monitored by swimming ability and spontaneous activity, showed no inter-group difference. The present results indicate that prenatal exposure to lidocaine fails to result in postnatal impairment of the development of behavioral performance of a wide range of tasks.

Selective attention and place navigation in rats treated prenatally with methylazoxymethanol

Prenatal treatment of rats on gestation day 15 with methylazoxymethanol (MAM) caused forebrain microencephaly. The behavioral analyses included measures of spontaneous motor activity and tests for cognitive deficits, and were performed when the rats had reached adult age. Female MAM-treated rats failed to demonstrate contextual control of latent inhibition, which confirms earlier findings with male rats. Male MAM-treated rats demonstrated a notable impairment of place navigation in a swim-maze, but showed as strong sensory preconditioning as the control animals. Biochemical analyses indicated considerable increases in catecholamine levels in the cerebral cortex, hippocampus and striatum. The cognitive deficits, characterised by the various conditioning (taste-aversion) and instrumental learning (swim-maze) tasks, suggested that the MAM rats are deficient in their capacity to attend selectively to the relevant stimulus in complex arrangements of the stimulus situation.

Selective lesioning of forebrain noradrenaline neurons at birth abolishes the improved maze learning performance induced by rearing in complex environment

The effect of selective destruction of forebrain noradrenaline (NA) neurons induced by 6-hydroxydopamine (6-OHDA) at Day 1 after birth on Hebb-Williams maze performance was investigated in adult rats housed after weaning in a complex environment (EC) or an isolated (IC) environment for 35 days. Saline treated control rats raised in the EC made fewer errors than those raised in the IC. This effect of EC was completely abolished in 6-OHDA treated rats; for these animals no improved performance due to the housing condition was obtained. Protection of the NA neurons against 6-OHDA neurotoxicity by pretreatment with desipramine (DMI) resulted in an effect of EC identical to that seen in saline-treated controls. Postweaning housing in the IC led to an increased locomotion as compared to housing in EC, but this effect was not affected by neonatal 6-OHDA and/or DMI treatment. Neurochemical analysis confirmed cortical NA and metabolite depletion as well as a good protection by the DMI pretreatment. The present results indicate that central NA neurons are involved critically in mediating mainly the cognitive components of behavioral alterations induced by EC.

Noradrenaline and the context-dependent extinction effect

Three experiments were performed to examine the effects of noradrenaline (NA) depletion upon the context-dependent extinction effects in conditioned taste-aversion learning. Three different methods were used to deplete NA: lesions of the dorsal noradrenergic bundle (DNAB) with 6-hydroxydopamine (6-OHDA), lesions induced by neonatal treatment with 6-OHDA and lesions induced by systemic administration with the NA neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). In each experiment, novel saccharin was presented in novel noisy bottle followed by lithium chloride. Later, during the extinction phase, half the control and half the NA depleted rats received saccharin in noisy bottles while the other half received saccharin in silent bottles. In the control condition, the rats that received saccharin in the noisy bottles (same context as conditioning) showed considerably more aversion than those that received saccharin in the silent bottles (different context to conditioning); NA depletion attenuated this effect. Reinstatement of the conditioning context (noisy bottle) resulted in a stronger aversion in the case where the different context (silent bottle) was present during extinction; this effect was attenuated in the NA depletion condition. These findings maintain a role for noradrenaline in compound conditioning tasks.

5-HT agonist induced analgesia modulated by central but not peripheral noradrenaline depletion in rats

The antinociceptive effect elicited by the 5-hydroxytryptamine (5-HT) agonist 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) was reversed or blocked in animals which had previously sustained severe spinal noradrenaline (NA) depletion via either systemic N-2-chlorethyl-N-ethyl-2-bromobenzylamine hydrochloride (DSP 4), neonatal 6-hydroxydopamine (neon. 6-OHDA), or intrathecal 6-OHDA treatment. Biochemical analysis of the lumbar spinal cord samples confirmed severe central NA depletions. Animals were tested with nondamaging heat pain (tail-flick test, hot-plate test) and electric footshock titration to determine the amount of antinociception or nociception. Peripheral NA depletion following intravenous (i.v.) 6-OHDA injection to adult rats had no effect on the antinociception induced by 5-MeODMT, but did cause severe NA depletions in the left heart atrium. These results suggest a modulatory effect of central and not peripheral noradrenergic system upon 5-HT agonist induced analgesia, and also give evidence that this effect is spinally mediated.

Role of central noradrenaline neurons in the contextual control of latent inhibition in taste aversion learning

Three experiments were performed to examine the effects of noradrenaline (NA) depletion, using 3 different methods: lesions of the dorsal noradrenergic bundle (DB) with 6-hydroxydopamine (6-OHDA), lesions induced by neonatal treatment with 6-OHDA and lesions induced by systemic DSP4 upon latent inhibition, using the taste-aversion learning procedure. NA depleted and control (sham, vehicle or saline) rats were given pre-exposure trials to either novel saccharin or to novel saccharin in a novel type of drinking bottle (the noisy bottle). Later, during conditioning trials saccharin was presented in the noisy bottles for all the rats, followed by lithium chloride injections. Saccharin aversions, tested for in the noisy bottles, indicated considerably weaker saccharin aversions (i.e. more latent inhibition) by the control groups pre-exposed to both saccharin and the noisy bottles. These context-dependent latent inhibition effects were clearly attenuated by all 3 treatments that depleted central NA. Biochemical assays confirmed the NA depletions in each case. The results, demonstrating the intimate role of central NA neurons in contextual control of latent inhibition in taste-aversion learning, appear to conform with current attentional theories of NA function in the forebrain.

The effect of selective noradrenergic lesions upon the stimulation by noradrenaline of inositol phospholipid breakdown in rat hippocampal miniprisms

The breakdown of inositol phospholipid (PI) stimulated by hippocampal noradrenaline in rat miniprisms in vitro was used as an index of alpha 1-adrenoceptor function after selective noradrenergic denervation. Selective denervation was produced by microinjections of 6-hydroxydopamine (6-OHDA) into either the dorsal noradrenergic bundle (DNAB) or the locus coeruleus (LC), or by systemic treatment with the noradrenergic neurotoxin DSP4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine). Fourteen days after these treatments, there was a large depletion of cortical noradrenaline but no change in the stimulation of hippocampal PI breakdown by noradrenaline. It is concluded that selective noradrenergic denervation under the conditions used here does not lead to hippocampal alpha 1-adrenoceptor supersensitivity as assessed by noradrenaline-stimulated PI breakdown.

Attenuation of sensory preconditioning by noradrenaline depletion in the rat

In order to investigate the effect of noradrenaline (NA) depletion upon an associative learning phenomenon, sensory preconditioning, rats were inflicted with either 6-hydroxydopamine-induced lesions of the dorsal noradrenergic bundle (DNAB) or the locus coeruleus (LC), or with systemic injections of the NA neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). Using appropriate controls (the UP groups) sensory preconditioning was demonstrated clearly in the non-lesion conditions (Sham or saline), but was blocked or strongly attenuated in the DNAB and DSP4 conditions. LC lesions did not affect sensory preconditioning. These findings suggest that the loss of central NA may cause some disruption of some aspects of complex associative learning. The role of NA in sensory preconditioning may be relevant to current notions of NA function.

Impaired selective attention in methylazoxymethanol-induced microencephalic rats

Prenatal treatment of rats on gestation day 15 with methylazoxymethanol (MAM) caused forebrain microencephaly. Several behavioral tests were performed when the rats had reached an adult age. MAM treated rats were hyperactive, and were severely impaired in the acquisition of successive position reversal in a T-maze. The microencephalic rats failed also to demonstrate contextual control of latent inhibition (the stimulus preexposure effect) in taste-aversion conditioning. These results indicate that MAM treatment disrupts attentional processes and that this may account for the learning impairment.

Central noradrenaline depletion attenuates amphetamine-induced locomotor behavior

Male rats were given 6-hydroxydopamine-induced lesions of the locus coeruleus (LC) or the dorsal noradrenergic bundle (DNAB), prior to the measurement of locomotor and rearing activity induced by D-amphetamine. The increased locomotor activity induced by D-amphetamine (1.8 mg/kg) was significantly attenuated by both the LC and the DNAB lesions. The stimulatory effect of the 7.2 mg/kg dose of amphetamine was attenuated by the LC lesion, whereas the DNAB lesion potentiated this effect. The LC lesion also attenuated rearing induced by the 7.2 mg/kg dose of amphetamine. These results suggest some involvement of central noradrenergic neurons in the activity induced by amphetamine in the rat.

Central noradrenaline depletion antagonizes aspects of d-amphetamine-induced hyperactivity in the rat

The effects of noradrenaline (NA) depletion upon amphetamine-induced hyperactivity were examined in five experiments. Central NA depletion via either systemic DSP4 or neonatal 6-OHDA antagonised the amphetamine-induced (2 mg/kg SC) increase in rearing behaviour, whereas lesions of the dorsal noradrenergic bundle using 6-hydroxydopamine antagonised the increase in locomotor activity. Peripheral NA depletion following systemic 6-hydroxydopamine to adult rats did not cause any changes in motor activity after acute amphetamine administration. Desipramine, the selective NA uptake inhibitor, blocked the effects of DSP4 upon amphetamine-induced rearing. NA depletion antagonised hyperactivity produced by the 2 mg/kg dose of amphetamine, but not the hyperactivity (rearing or locomotion) effects of amphetamine at 1, 4 or 8 mg/kg.

The hindlimb extension reflex is not a reliable marker of post-decapitation convulsions or spinal noradrenaline depletion in rats

The degree of hindlimb extension reflex (ER), post-decapitation reflex (PDR) and noradrenaline (NA) depletion was measured under various treatment regimens involving the neurotoxins DSP4 and 6-OHDA. Neither neonatal 6-OHDA treatment, direct application of 6-OHDA to the locus coeruleus nor DSP4 treatment produced a blockade of ER that could be associated with the loss of PDR and the spinal NA depletion, whereas intrathecal 6-OHDA treatment caused a strong loss of both ER and PDR related to severe spinal NA depletion. No correlation was obtained between the ER and PDR in a large number of DSP4-treated rats.

Latent inhibition following systemic DSP4: effects due to presence and absence of contextual cues in taste-aversion learning

Three taste-aversion experiments were performed to test the effect of noradrenaline (NA) depletion, following systemic administration of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4), upon the Lubow "latent inhibition" effect in rats. DSP4-treated rats did not demonstrate any attenuation of latent inhibition, the conditioned stimulus (CS) preexposure effect. Instead, when the contextual conditions (provided by a noise-producing bottle) were so arranged that there was a "mismatch" from the saccharin preexposure to the saccharin-aversion conditioning phase, the DSP4 rats showed some considerable enhancement of latent inhibition. This disruption of the contextual control of the degree of latent inhibition evinced by the NA-depleted rats was found to bear a striking resemblance to the attenuated contextual control of extinction in taste aversion by DSP4 treated rats demonstrated earlier. Biochemical analysis of noradrenaline and serotonin accumulation performed after Experiment 1, and postdecapitation reflex analysis after each experiment, confirmed the selective NA depletion. These results are compared to earlier findings concerning noradrenaline and latent inhibition and the effects are discussed with reference to selective attentional and retrieval-based models of noradrenaline function in learning and memory.

T-maze learning, spontaneous activity and food intake recovery following systemic administration of the noradrenaline neurotoxin, DSP4

Following systemic administration of the noradrenaline (NA) neurotoxin, DSP4 (50 mg/kg), rats were found to be retarded in the rate at which they acquired the "right-turn" running response in a modified T-maze choice situation, as measured by the total number of errors per session and median latency to reach the goal box. Desipramine (DMI, 20 mg/kg), injected 30 min before DSP4 blocked the acquisition retardation. DSP4 was found to have a short-lasting effect upon spontaneous motor activity, while food and water intake recovery was complete within 7 days of the injection. Both the NA-accumulation data and endogenous NA concentrations indicated profound NA, but not 5-hydroxytryptamine (5-HT) and dopamine (DA), depletions in the cortex, hippocampus and cerebellum. These data seem to confirm the role of the locus coeruleus-noradrenaline (LC-NA) system in an instrumental learning situation.