Depressive-like behavior is paired to monoaminergic alteration in a murine model of Alzheimer's disease

Background: Neuropsychiatric signs are critical in primary caregiving of Alzheimer patients and have not yet been fully investigated in murine models. Methods: 18-month-old 3.Tg-AD Male mice and their wild-type Male littermates (non-Tg) were used. The open field test and the elevated plus maze test were used to evaluate anxiety-like behaviors, whereas the Porsolt forced swim test, the tail suspension test, and the sucrose preference test for antidepressant/depression-coping behaviors. Neurochemical study was conducted by microdialysis in freely-moving mice, analyzing the basal and K+-stimulated monoamine output in the frontal cortex and ventral hippocampus. Moreover by immunohistochemistry, we analysed the expression of Tyrosin hydroxylase and Tryptophan hydroxylase, which play a key role in the synthesis of monoamines. Results: Aged 3.Tg-AD mice exhibited a higher duration of immobility in the forced swim and tail suspension tests (predictors of depression-like behavior) which was not attenuated by a noradrenaline reuptake inhibitor, desipramine. In the sucrose preference test, 3.Tg-AD mice showed a significantly lower sucrose preference compared to the non-Tg group, without any difference in total fluid intake. In contrast, the motor functions and anxiety-related emotional responses of 3.Tg-AD mice were normal, as detected by the open-field and elevated plus-maze tests. To strengthen these results, we then evaluated the monoaminergic neurotransmissions by in vivo microdialysis and immunohistochemistry. In particular, with the exception of the basal hippocampal dopamine levels, 3.Tg-AD mice exhibited a lower basal extracellular output of amines in the frontal cortex and ventral hippocampus and also a decreased extracellular response to K+ stimulation. Such alterations occur with obvious local amyloid-β and tau pathologies and without gross alterations in the expression of Tyrosin and Tryptophan hydroxylase. Conclusions: These results suggest that 3.Tg-AD mice exhibit changes in depression-related behavior involving aminergic neurotrasmitters and provide an animal model for investigating AD with depression

MUCOADHESIVE MICROSPHERES: AN EMINENT ROLE IN CONTROLLED DRUG DELIVERY

ABSTRACT Mucoadhesion is simply known as interfacial force interactions between polymeric materials and mucosal tissues. In the last two decades mucoadhesive microspheres have received considerable attention for design of novel drug delivery systems due to their ability to prolong the residence time of dosage forms and to enhance drug bioavailability. Mucoadhesive microspheres have advantages like efficient absorption and enhanced bioavailability of the drugs due to a high surface to volume ratio, a much more intimate contact with the mucus layer, controlled and sustained release of drug from dosage form and specific targeting of drugs to the absorption site. Microspheres are the carrier linked drug delivery system in which particle size is ranges from 1-1000 μm range in diameter having a core of drug and entirely outer layers of polymer as coating material. Keywords: mucoadhesion, microspheres, controlled release, residence time. INTRODUCTION Since many years several kinds of diseases that may be acute or chronic diseases can be treated by using pharmaceutical dosage form like solutions, tablets, capsules, syrups, suspension, emulsion, ointments, creams, gels which can be used as orally, topically, or intravascular route. To get the proper therapeutic effect of these pharmaceutical dosage forms they should be administered several times a day, this results consequently undesirable toxicity, fluctuation in drug level and poor efficiency or therapeutic effect. Controlled release dosage form plays eminent role to overcome the problems which are discussed above. The most important example of controlled drug delivery system is mucoadhesive microspheres which can improve the therapeutic effect of administered drug. Also bioavailability of drug is also better than other conventional system because mucoadhesive microspheres remain close to the mucous membrane and absorption tissue. Drug delivery systems (DDS) that can precisely control the release rates or target drugs to a specific body site have had an enormous impact on the healthcare system. The last two and developing novel delivery systems referred to as "mucoadhesive microspheres". [1] Physiology of mucin Mucus is produced in the eye, ear, nose and mouth. It also lines the respiratory, gastrointestinal and reproductive tracts. Its primary functions are the protection and lubrication of the underlying epithelium. Human cervical mucus, for instance, plays an integral role in both conception and contraception. It is essential to understand the structure and physical chemistry of mucus if the latter is to be exploited as a site for bioadhesive controlled drug release. Since the gastrointestinal tract is the primary site for drug absorption, the physiology of this site will be the focus of this discussion. The gelling properties which are essential to the function of mucus are the direct result of the glycoprotein present in the mucosal secretion. This glycoprotein is generally the same for various secretion sites within the body; however, specific and subtle biochemical differences have been identified. Mucus may be either constantly or intermittently secreted. The amount of mucus secreted also varies. The glycoproteinic component of mucus is a high molecular weight, highly glycosylated macromolecular system. This polydisperse natural polymer makes up between 0.5 and 5% of the fully hydrated mucus secretion. [10] The size of the intact molecule is approximately 1.8 x 10 6 , but the molecular weight of undegraded gastric mucin is as high as 4.5 x 10 7 . These macromolecules are highly expanded random coils made up of monomeric glycoproteins which for humans range from 5.5 x 1o 5 in the stomach to 2.4 x lo 5 in the small intestine. Oligosaccharide branches are attached to 63% of the protein core while the remainder of There are 34 disulphide bridges per molecule of rat goblet cell mucin, which has a molecular weight of 2 x 10 6 , while porcine intestinal mucin has 28 bridges per molecule. Human mucin has a similar density of disulphide bonds. The protein spine of the macromolecule has about 800 amino acid residues. Sugar chains are attached at about every three residues along the glycosylated regions; this results in approximately 200 side chains per molecule. This molecule is resistant to proteolytic attack in the glycosylated regions only. Thus, charge interactions may have a significant effect on the behaviour of mucus glycoproteins. The mucous gel covering the epithelium varies in thickness. In the human stomach, the mean thickness is 192 pm, while in the duodenum the thickness ranges from 10 to 400 pm In the gastrointestinal tract, mucus facilitates the passage of food and boluses through the alimentary canal. It also helps shield the epithelium from shear forces induced by peristaltic waves, and resists auto digestion. These functions are promoted by the constant secretion of mucus to replenish losses from turbulence and degradation. In response to an irritant, the amount of acidic side chains in the glycoprotein increases from 50 to 80%, making the macromolecule more negatively charged. The submucosal gland layer increases in depth and the number of goblet cells increases. The total content of non dialysable solids and pH also increase. In the GI tract, DNA and albumin thicken mucus in the diseased state. Mucosal irritation, such as exposure to alcohol or bile salts, elicits accelerated mucin release. Disease can significantly alter the nature and thickness of the mucus. This may lead to a change in the behaviour of the delivery system. Any drug delivery system which is intended to adhere to the mucus epithelium will need to adapt to a substrate which varies in depth and consistency, and may also change biochemically. Hypersecretion, which is more common than hyposecretion during disease, increases the transit rate through the GI tract, and thus reduces the residence time of a mucoadhesive device. Thus, it is essential to consider the physiology of the system when optimizing the formulation of an adhesive controlled release device. CLASSIFICATION OF MUCOADHESIVE POLYMERS Mucoadhesion is defined as interfacial force interactions between polymeric materials and mucosal tissues. In the last two decades mucoadhesive polymers have received considerable attention for design of novel drug delivery systems due to their ability to prolong the residence time of dosage forms and to enhance drug bioavailability. Various administration routes, such as ocular, nasal, gastrointestinal, vaginal and rectal, make mucoadhesive drug delivery systems attractive and flexible in dosage forms development. Mucoadhesive polymers can be classified as,- I. Traditional non-specific first-generation mucoadhesive polymers First-generation mucoadhesive polymers may be divided into three main subsets, namely: (1) Anionic polymers:-Anionic polymers are widely employed for its greatest mucoadhesive strength and low toxicity. These polymers are characterised by the presence of sulphate and carboxyl group that gives rise to net negative charge at PH values exceeding the pka of polymer. Example:-polyacrylic acid (PAA) & its weakly cross linked derivatives, Sodium carboxymethyl cellulose (NACMC) [30] (2) Cationic polymers: -The most conveniently and widely used cationic polymer is chitosan which is produced by deacetylation of chitin. Chitin is a natural polysaccharide found predominantly in the shells of crustaceans such as crabs and shrimp, the cuticles of insects, and the cell walls of fungi. It is one of the most abundant biopolymers next to cellulose Most of the naturally occurring polysaccharides, e.g. cellulose, dextran, pectin, alginic acid, agar, agarose and carrageenans, are neutral or acidic in nature, whereas chitin and chitosan are examples of highly basic polysaccharides. The unique properties include II.Novel second-generation mucoadhesive polymers: The major disadvantage in using traditional nonspecific mucoadhesive systems (first generation) is that adhesion may occur at sites other than those intended. Unlike first-generation non-specific platforms, certain second-generation polymer platforms are less susceptible to mucus turnover rates, with some species binding directly to mucosal surfaces; more accurately termed ''cytoadhesives". Furthermore as surface carbohydrate and protein composition at potential target sites vary regionally, more accurate drug delivery may be achievable. MUCOADHESION Due its relative complexity, it is likely that the process of mucoadhesion cannot be described by just one of these theories. In considering the mechanism of mucoadhesion, a whole range 'scenarios' for in-vivo mucoadhesive bond formation are possible. These include: A). Dry or partially hydrated dosage forms contacting surfaces with substantial mucus layers (typically particulates administered into the nasal cavity). B). fully hydrated dosage forms contacting surfaces with substantial mucus layers (typically particulates of many 'First Generation'mucoadhesives that have hydrated in the luminal contents on delivery to the lower gastrointestinal tract). C). Dry or partially hydrated dosage forms contacting surfaces with thin/discontinuous mucus layers (typically tablets or patches in the oral cavity or vagina). D). fully hydrated dosage forms contacting surfaces with thin/discontinuous mucus layers (typically aqueous semisolids or liquids administered into the oesophagus or eye). It is unlikely that the mucoadhesive process will be the same in each case. In the study of adhesion generally, two steps in the adhesive process have been identified Step 2 -Consolidation stage: Various physicochemical interactions occur to consolidate and strengthen the adhesive joint, leading to prolonged adhesion. THEORIES ON MUCOADHESION [4, 5] Various kinds of theories are there which can explain the mechanism of mucoadhesion they are discussed below, TYPES OF MICROSPHERES Mucoadhesive microspheres:-Adhesion can be defined as sticking of drug to the membrane by using the sticking property of the water soluble polymers. Adhesion of drug delivery device to the mucosal membrane such as buccal, ocular, rectal, nasal etc can be termed as bio -adhesion. These kinds of microspheres exhibit a prolonged residence time at the site of application and causes intimate contact with the absorption site and produces better therapeutic action. [26] Magnetic microspheres:-This kind of delivery system is very much important which localises the drug to the disease site. In this larger amount of freely circulating drug can be replaced by smaller amount of magnetically targeted drug. Magnetic carriers receive magnetic responses to a magnetic field from incorporated materials that are used for magnetic microspheres are chitosan, dextran etc. The different type are, Therapeutic magnetic microspheres: Are used to deliver chemotherapeutic agent to liver tumour. Drugs like proteins and peptides can also be targeted through this system.6 Diagnostic microspheres: Can be used for imaging liver metastases and also can be used to distinguish bowel loops from other abdominal structures by forming nano size particles supramagnetic iron oxides. Floating microspheres:-In this type of microspheres the bulk density is less than the gastric fluid and so remains buoyant in stomach without affecting gastric emptying rate. The release rate of drug is slow at the desired rate, if the system is floating on gasteric content and increases gastric residence and increases fluctuation in plasma concentration

Role of the basolateral amygdala in mediating the effects of the fatty acid amide hydrolase inhibitor URB597 on HPA axis response to stress.

The endocannabinoid system is an important regulator of neuroendocrine and behavioral adaptation in stress related disorders thus representing a novel potential therapeutic target. The aim of this study was to determine the effects of the fatty acid amide hydrolase (FAAH) inhibitor URB597 on stress mediators of HPA axis and to study the role of the basolateral amygdala (BLA) in responses to forced swim stress. Systemic administration of URB597 (0.1 and 0.3mg/kg) reduced the forced swim stress-induced activation of HPA axis. More specifically, URB597 decreased stress-induced corticotropin-releasing hormone (CRH) mRNA expression in the paraventricular nucleus (PVN) of the hypothalamus, and pro-opiomelanocortin (POMC) mRNA expression dose-dependently in pituitary gland without affecting plasma corticosterone levels. URB597 treatment also attenuated stress-induced neuronal activation of the amygdala and PVN, and increased neuronal activation in the locus coeruleus (LC) and nucleus of solitary tract (NTS). Injection of the CB1 receptor antagonist AM251 (1ng/side) in the BLA significantly attenuated URB597-mediated effects in the PVN and completely blocked those induced in the BLA. These results suggest that the BLA is a key structure involved in the anti-stress effects of URB597, and support the evidence that enhancement of endogenous cannabinoid signaling by inhibiting FAAH represents a potential therapeutic strategy for the management of stress-related disorders

Role of the basolateral amygdala in mediating the effects of the fatty acid amide hydrolase inhibitor URB597 on HPA axis response to stress

The endocannabinoid system is an important regulator of neuroendocrine and behavioral adaptation in stress related disorders thus representing a novel potential therapeutic target. The aim of this study was to determine the effects of the fatty acid amide hydrolase (FAAH) inhibitor URB597 on stress mediators of HPA axis and to study the role of the basolateral amygdala (BLA) in responses to forced swim stress. Systemic administration of URB597 (0.1 and 0.3mg/kg) reduced the forced swim stress-induced activation of HPA axis. More specifically, URB597 decreased stress-induced corticotropin-releasing hormone (CRH) mRNA expression in the paraventricular nucleus (PVN) of the hypothalamus, and pro-opiomelanocortin (POMC) mRNA expression dose-dependently in pituitary gland without affecting plasma corticosterone levels. URB597 treatment also attenuated stress-induced neuronal activation of the amygdala and PVN, and increased neuronal activation in the locus coeruleus (LC) and nucleus of solitary tract (NTS). Injection of the CB1 receptor antagonist AM251 (1ng/side) in the BLA significantly attenuated URB597-mediated effects in the PVN and completely blocked those induced in the BLA. These results suggest that the BLA is a key structure involved in the anti-stress effects of URB597, and support the evidence that enhancement of endogenous cannabinoid signaling by inhibiting FAAH represents a potential therapeutic strategy for the management of stress-related disorders

Biological mechanisms associated with increased perseveration and hyperactivity in a genetic mouse model of neurodevelopmental disorder

Chromosomal deletions at Xp22.3 appear to influence vulnerability to the neurodevelopmental disorders attention deficit hyperactivity disorder (ADHD) and autism. 39,X(Y*)O mice, which lack the murine orthologue of the Xp22.3 ADHD candidate gene STS (encoding steroid sulfatase), exhibit behavioural phenotypes relevant to such disorders (e.g. hyperactivity), elevated hippocampal serotonin (5-HT) levels, and reduced serum levels of dehydroepiandrosterone (DHEA). Here we initially show that 39,X(Y*)O mice are also deficient for the recently-characterised murine orthologue of the Xp22.3 autism candidate gene ASMT (encoding acetylserotonin-O-methyltransferase). Subsequently, to specify potential behavioural correlates of elevated hippocampal 5-HT arising due to the genetic lesion, we compared 39,X(Y*)O MF1 mice to 40,XY MF1 mice on behavioural tasks taxing hippocampal and/or 5-HT function (a 'foraging' task, an object-location task, and the 1-choice serial reaction time task of impulsivity). Although Sts/Asmt deficiency did not influence foraging behaviour, reactivity to familiar objects in novel locations, or 'ability to wait', it did result in markedly increased response rates; these rates correlated with hippocampal 5-HT levels and are likely to index behavioural perseveration, a frequent feature of neurodevelopmental disorders. Additionally, we show that whilst there was no systematic relationship between serum DHEA levels and hippocampal 5-HT levels across 39,X(Y*)O and 40,XY mice, there was a significant inverse linear correlation between serum DHEA levels and activity. Our data suggest that deficiency for genes within Xp22.3 could influence core behavioural features of neurodevelopmental disorders via dissociable effects on hippocampal neurochemistry and steroid hormone levels, and that the mediating neurobiological mechanisms may be investigated in the 39,X(Y*)O model

Depressive-like behavior is paired to monoaminergic alteration in a murine model of Alzheimer's disease

BACKGROUND: Neuropsychiatric signs are critical in primary caregiving of Alzheimer patients and have not yet been fully investigated in murine models. METHODS: 18-month-old 3×Tg-AD male mice and their wild-type male littermates (non-Tg) were used. The open field test and the elevated plus maze test were used to evaluate anxiety-like behaviors, whereas the Porsolt forced swim test, the tail suspension test, and the sucrose preference test for antidepressant/depression-coping behaviors. Neurochemical study was conducted by microdialysis in freely-moving mice, analyzing the basal and K(+)-stimulated monoamine output in the frontal cortex and ventral hippocampus. Moreover by immunohistochemistry, we analysed the expression of Tyrosin hydroxylase and Tryptophan hydroxylase, which play a key role in the synthesis of monoamines. RESULTS: Aged 3×Tg-AD mice exhibited a higher duration of immobility in the forced swim and tail suspension tests (predictors of depression-like behavior) which was not attenuated by a noradrenaline reuptake inhibitor, desipramine. In the sucrose preference test, 3×Tg-AD mice showed a significantly lower sucrose preference compared to the non-Tg group, without any difference in total fluid intake. In contrast, the motor functions and anxiety-related emotional responses of 3×Tg-AD mice were normal, as detected by the open-field and elevated plus-maze tests. To strengthen these results, we then evaluated the monoaminergic neurotransmissions by in vivo microdialysis and immunohistochemistry. In particular, with the exception of the basal hippocampal dopamine levels, 3×Tg-AD mice exhibited a lower basal extracellular output of amines in the frontal cortex and ventral hippocampus and also a decreased extracellular response to K(+) stimulation. Such alterations occur with obvious local amyloid-β and tau pathologies and without gross alterations in the expression of Tyrosin and Tryptophan hydroxylase. CONCLUSIONS: These results suggest that 3×Tg-AD mice exhibit changes in depression-related behavior involving aminergic neurotrasmitters and provide an animal model for investigating AD with depression

Depressive-Like Behavior Is Paired to Monoaminergic Alteration in a Murine Model of Alzheimer's Disease.

BACKGROUND: Neuropsychiatric signs are critical in primary caregiving of Alzheimer patients and have not yet been fully inves tigated in murine models. METHODS: 18-month-old 3×Tg-AD male mice and their wild-type male littermates (non-Tg) were used. The open field test and the elevated plus maze test were used to evaluate anxiety-like behaviors, whereas the Porsolt forced swim test, the tail suspension test, and the sucrose preference test for antidepressant/depression-coping behaviors. Neurochemical study was conducted by microdialysis in freely-moving mice, analyzing the basal and K+-stimulated monoamine output in the frontal cortex and ventral hippocampus. Moreover by immunohistochemistry, we analysed the expression of Tyrosin hydroxylase and Tryptophan hydroxylase, which play a key role in the synthesis of monoamines. RESULTS: Aged 3×Tg-AD mice exhibited a higher duration of immobility in the forced swim and tail suspension tests (predictors of depression-like behavior) which was not attenuated by a noradrenaline reuptake inhibitor, desipramine. In the sucrose preference test, 3×Tg-AD mice showed a significantly lower sucrose preference compared to the non-Tg group, without any difference in total fluid intake. In contrast, the motor functions and anxiety-related emotional responses of 3×Tg-AD mice were normal, as detected by the open-field and elevated plus-maze tests. To strengthen these results, we then evaluated the monoaminergic neurotransmissions by in vivo microdialysis and immunohistochemistry. In particular, with the exception of the basal hippocampal dopamine levels, 3×Tg-AD mice exhibited a lower basal extracellular output of amines in the frontal cortex and ventral hippocampus and also a decreased extracellular response to K+ stimulation. Such alterations occur with obvious local amyloid-β and tau pathologies and without gross alterations in the expression of Tyrosin and Tryptophan hydroxylase. CONCLUSIONS: These results suggest that 3×Tg-AD mice exhibit changes in depression-related behavior involving aminergic neurotrasmitters and provide an animal model for investigating AD with depression

High dietary fat intake influences the activation of specific hindbrain and hypothalamic nuclei by the satiety factor oleoylethanolamide

Chronic exposure to a diet rich in fats changes the gastrointestinal milieu and alters responses to several signals involved in the control of food intake. Oleoylethanolamide (OEA) is a gut-derived satiety signal released from enterocytes upon the ingestion of dietary fats. The anorexigenic effect of OEA, which requires intestinal PPAR-alpha receptors and is supposedly mediated by vagal afferents, is associated with the induction of c-fos in several brain areas involved in the control of food intake, such as the nucleus of the solitary tract (NST) and the hypothalamic paraventricular (PVN) and supraoptic nuclei (SON). In the present study we investigated whether the exposure to a high fat diet (HFD) alters the hindbrain and hypothalamic responses to OEA. To this purpose we evaluated the effects of OEA at a dose that reliably inhibits eating (10mg/kg i.p.) on the induction of c-fos in the NST, area postrema (AP), PVN and SON in rats maintained either on standard chow or a HFD. We performed a detailed analysis of the different NST subnuclei activated by i.p. OEA and found that peripheral OEA strongly activates c-fos expression in the AP, NST and in the hypothalamus of both chow and HFD fed rats. The extent of c-fos expression was, however, markedly different between the two groups of rats, with a weaker activation of selected NST subnuclei and stronger activation of the PVN in HFD-fed than in chow-fed rats. HFD-fed rats were also more sensitive to the immediate hypophagic action of OEA than chow-fed rats. These effects may be due to a decreased sensitivity of vagal afferent fibers that might mediate OEA's actions on the brain and/or an altered sensitivity of brain structures to OEA

Inhibition of anandamide hydrolysis enhances noradrenergic and GABAergic transmission in the prefrontal cortex and basolateral amygdala of rats subjected to acute swim stress.

Limbic forebrain endocannabinoid (eCB) signaling is critically involved in stress integration by modulating neurotransmitters release. The purpose of this study was to examine, by brain microdialysis, the effects of fatty acid amide hydrolase (FAAH) inhibition on noradrenergic and γ-aminobutyric acid (GABA)-ergic neurotransmission in the prefrontal cortex (PFC) and basolateral amygdala (BLA) of rats subjected to a 20-min swim stress. Microdialysis started on stress- and drug-naïve rats that were treated with the FAAH inhibitor URB597 (0.1 or 0.3 mg/kg) 30 min before undergoing the stress procedure. Dialysate samples were collected every 20 min from the beginning of the experiment. Concentrations of noradrenaline (NA) and GABA were determined by HPLC coupled to electrochemical and fluorescence detection, respectively. We found that neither URB597 treatment nor 20 min of swim stress exposure per se altered NA and GABA extracellular levels in PFC or BLA. Interestingly, rats treated with 0.1 mg/kg of URB597 followed by 20 min of stress showed significantly higher NA and GABA levels in PFC and BLA. These effects were absent in rats treated with 0.3 mg/kg URB597, indicating a dose-specific effect. Moreover, we found that the pretreatment with the CB1 receptor antagonist rimonabant blocked the URB597 effects on NA and GABA release in PFC and BLA of animals subjected to forced swimming. The present study might provide an important first step toward understanding the mechanisms through which URB597 modulates stress-induced neuroendocrine secretion and behavioral coping strategies