Reduction of acethylcolinesterase activity in the brain of mdx mice

Lack of dystrophin in brain structures have been involved with impaired cognitive functions. Acethylcolinesterase (AChE) is implicated in many cognitive functions and probably plays important roles in neurodegenerative disorders. In the present study, we investigated AChE activity in the prefrontal cortex, hippocampus, striatum and cortex of mdx mice. To this aim, brain tissues from male dystrophic mdx and normal control mice were used. We observed that mdx mice display a reduction in AChE activity of 40-60% in all brain structures evaluated. In conclusion, dystrophin deficiency may be affecting AChE activity and contributing negatively, in part, to memory storage and restoring. (C) 2011 Elsevier B.V. All rights reserved.

Dissecting the brain`s fear system reveals the hypothalamus is critical for responding in subordinate conspecific intruders

Effective defense against natural threats in the environment is essential for the survival of individual animals. Thus, instinctive behavioral responses accompanied by fear have evolved to protect individuals from predators and from opponents of the same species (dominant conspecifics). While it has been suggested that all perceived environmental threats trigger the same set of innately determined defensive responses, we tested the alternate hypothesis that different stimuli may evoke differentiable behaviors supported by distinct neural circuitry. The results of behavioral, neuronal immediate early gene activation, lesion, and neuroanatomical experiments indicate that the hypothalamus is necessary for full expression of defensive behavioral responses in a subordinate conspecific, that lesions of the dorsal premammillary nucleus drastically reduce behavioral measures of fear in these animals, and that essentially separate hypothalamic circuitry supports defensive responses to a predator or a dominant conspecific. It is now clear that differentiable neural circuitry underlies defensive responses to fear conditioning associated with painful stimuli, predators, and dominant conspecifics and that the hypothalamus is an essential component of the circuitry for the latter two stimuli.

Insights on eukaryotic translation initiation factor 5A (eIF5A) in the brain and aging

Long-term memory, a persistent form of synaptic plasticity, requires translation of a subset of mRNA present in neuronal dendrites during a short and critical period through a mechanism not yet fully elucidated. Western blotting analysis revealed a high content of eukaryotic translation initiation factor 5A (eIF5A) in the brain of neonatal rats, a period of intense neurogenesis rate, differentiation and synaptic establishment, when compared to adult rats. Immunohistochemistry analysis revealed that eIF5A is present in the whole brain of adult rats showing a variable content among the cells from different areas (e.g. cortex, hippocampus and cerebellum). A high content of eIF5A in the soma and dendrites of Purkinje cells, key neurons in the control of motor long-term memory in the cerebellum, was observed. Detection of high eIF5A content was revealed in dendritic varicosities of Purkinje cells. Evidence is presented herein that a reduction of eIF5A content is associated to brain aging. (C) 2008 Elsevier B.V. All rights reserved.

Trypanosoma evansi: Adenosine deaminase activity in the brain of infected rats

The study was undertaken to evaluate changes in the activity of adenosine deaminase (ADA) in brains of rats infected by Trypanosoma evansi. Each rat was intraperitoneally infected with 10(6) trypomastigotes either suspended in fresh (group A; n = 13) and cryopreserved blood (group B; n = 13). Thirteen animals were used as control (group C). ADA activity was estimated in the cerebellum, cerebral cortex, striatum and hippocampus. No differences (P > 0.05) in ADA activity were observed in the cerebellum between infected and non-infected animals. Significant (P < 0.05) reductions in ADA activity occurred in cerebral cortex in acutely (day 4 post-infection; PI) and chronically (day 20 PI) infected rats. ADA activity was significantly (P < 0.05) decreased in the hippocampus in acutely infected rats, but significantly (P < 0.05) increased in the chronically infected rats. Significant (P < 0.05) reductions in ADA activity occurred in the striatum of chronically infected rats. Parasites could be found in peripheral blood and brain tissue through microscopic examination and PCR assay, respectively, in acutely and chronically infected rats. The reduction of ADA activity in the brain was associated with high levels of parasitemia and anemia in acute infections. Alterations in ADA activity of the brain in T. evansi-infected rats may have implications for pathogenesis of the disease. (C) 2010 Elsevier Inc. All rights reserved.

Leptin Targets in the Mouse Brain

The central actions of leptin are essential for homeostatic control of adipose tissue mass, glucose metabolism, and many autonomic and neuroendocrine systems. In the brain, leptin acts on numerous different cell types via the long-form leptin receptor (LepRb) to elicit its effects. The precise identification of leptin`s cellular targets is fundamental to understanding the mechanism of its pleiotropic central actions. We have systematically characterized LepRb distribution in the mouse brain using in situ hybridization in wildtype mice as well as by EYFP immunoreactivity in a novel LepRb-IRES-Cre EYFP reporter mouse line showing high levels of LepRb mRNA/EYFP coexpression. We found substantial LepRb mRNA and EYFP expression in hypothalamic and extrahypothalamic sites described before, including the dorsomedial nucleus of the hypothalamus, ventral premammillary nucleus, ventral tegmental area, parabrachial nucleus, and the dorsal vagal complex. Expression in insular cortex, lateral septal nucleus, medial preoptic area, rostral linear nucleus, and in the Edinger-Westphal nucleus was also observed and had been previously unreported. The LepRb-IRES-Cre reporter line was used to chemically characterize a population of leptin receptor-expressing neurons in the midbrain. Tyrosine hydroxylase and Cre reporter were found to be coexpressed in the ventral tegmental area and in other midbrain dopaminergic neurons. Lastly, the LepRbI-RES-Cre reporter line was used to map the extent of peripheral leptin sensing by central nervous system (CNS) LepRb neurons. Thus, we provide data supporting the use of the LepRb-IRES-Cre line for the assessment of the anatomic and functional characteristics of neurons expressing leptin receptor. J. Comp. Neurol. 514:518-532, 2009. (C) 2009 Wiley-Liss, Inc.

Exercise-induced plasticity of AMPA-type glutamate receptor subunits in the rat brain

The aim of this study was to analyze the plastic effects of moderate exercise upon the motor cortex (M1 and M2 areas), cerebellum (Cb), and striatum (CPu) of the rat brain This assessment was made by verifying the expression of AMPA type glutamate receptor subunits (GluR1 and GluR2/3) We used adult Wistar rats, divided into 5 groups based on duration of exercise training, namely 3 days (EX3), 7 days (EX7) 15 days (EX15) 30 days (EX30), and sedentary (S) The exercised animals were subjected to a treadmill exercise protocol at the speed of the 10 meters/min for 40 mm After exercise, the brains were subjected to immunohistochemistry and immunoblotting to analyze changes of GluR1 and GluR2/3, and plasma cortcosterone was measured by ELISA in order to verify potential stress induced by physical training Overall the results of immunohistochemistry and immunoblotting were similar and revealed that GluR subunits show distinct responses over the exercise periods and for the different structures analyzed In general, there was increased expression of GluR subunits after longer exercise periods (such as EX30) although some opposite effects were seen after short periods of exercise (Ex3) In a few cases biphasic patterns with decreases and subsequent increases of GluR expression were seen and may represent the outcome of exercise dependent, complex regulatory processes The data show that the protocol used was able to promote plastic GluR changes during exercise, suggesting a specific involvement of these receptors in exercise induced plasticity processes in the brain areas tested (C) 2010 Elsevier B V All rights reserved

Eag 1, Eag 2 and Kcnn3 gene brain expression of isolated reared rats

The Eag1 and Eag2, voltage-dependent potassium channels, and the small-conductance calcium-activated potassium channel (Kcnn3) are highly expressed in limbic regions of the brain, where their function is still unknown. Eag1 co-localizes with tyrosine hydroxilase enzyme in the substantia nigra and ventral tegmental area. Kcnn3 deficiency leads to enhanced serotonergic and dopaminergic neurotransmission accompanied by distinct alterations in emotional behaviors. As exposure to stress is able to change the expression and function of several ion channels, suggesting that they might be involved in the consequences of stress, we aimed at investigating Eag 1, Eag2 and Kcnn3 mRNA expression in the brains of rats submitted to isolation rearing. As the long-lasting alterations in emotional and behavioral regulation after stress have been related to changes in serotonergic neurotransmission, expressions of serotonin Htr1a and Htr2a receptors in male Wistar rats` brain were also investigated. Rats were reared in isolation or in groups of five for nine weeks after weaning. Isolated and socially reared rats were tested for exploratory activity in the open field test for 5 min and brains were processed for reverse-transcription coupled to quantitative polymerase chain reaction (qRT-PCR). Isolated reared rats showed decreased exploratory activity in the open field. Compared to socially reared rats, isolated rats showed reduced Htr2a mRNA expression in the striatum and brainstem and reduced Eag2 mRNA expression in all examined regions except cerebellum. To our knowledge, this is the first work to show that isolation rearing can change Eag2 gene expression in the brain. The involvement of this channel in stress-related behaviors is discussed.

Sexually Dimorphic Effect of the Val66Met Polymorphism of BDNF on Susceptibility to Alzheimer`s Disease: New Data and Meta-Analysis

Conflicting results have been reported as to whether genetic variations (Val66Met and C270T) of the brain-derived neurotrophic factor gene (RDNF) confer susceptibility to Alzheimer`s disease (AD). We genotyped these polymorphisms in a Japanese sample of 657 patients with AD and 525 controls, and obtained weak evidence of association for Val66Met (P = 0.063), but not for C270T. After stratification by sex, we found a significant allelic association between Val66Met and AD in women (P = 0.017), but not in men. To confirm these observations, we collected genotyping data for each sex from 16 research centers worldwide (4,711 patients and 4,537 controls in total). The meta-analysis revealed that there was a clear sex difference in the allelic association; the Met66 allele confers susceptibility to AD in women (odds ratio = 1.14, 95% CI 1.05-1.24, P = 0.002), but not in men. Our results provide evidence that the Met66 allele of BDNF has a sexually dimorphic effect on susceptibility to AD. (C) 2009 Wiley-Liss, Inc.

Striatum brain-derived neurotrophic factor levels are decreased in dystrophin-deficient mice

Brain dystrophin is enriched in the postsynaptic densities of pyramidal neurons specialized regions of the subsynaptic cytoskeletal network, which are critical for synaptic transmission and plasticity. Lack of dystrophin in brain structures have been involved with impaired cognitive functions. The brain-derived neurotrophic factor (BDNF) is a regulator of neuronal survival, fast synaptic transmission, and activity-dependent synaptic plasticity. The present study investigated BDNF protein levels by Elisa analysis in prefrontal cortex, cerebellum, hippocampus, striatum and cortex tissues from male dystrophic mdx (n = 5) and normal C57BL10 mouse (n = 5). We observed that the mdx mouse display diminution in BDNF levels in striatum (t = 6.073; df = 6; p = 0.001), while a tendency of decrease in BDNF levels was observed in the prefrontal cortex region (t = 1.962; df = 6; p = 0.096). The cerebellum (t = 1.258; df = 7; p = 0.249), hippocampus (t = 0.631; df = 7; p = 0.548) and cortex (t = 0.572; df = 7; p = 0.586) showed no significant alterations as compared to wt mouse. In conclusion, we demonstrate that only striatum decreased BDNF levels compared with wild-type (wt) mouse, differently to the other areas of the brain. This dystrophin deficiency may be affecting BDNF levels in striatum and contributing, in part, in memory storage and restoring. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Acquisition of Pavlovian Fear Conditioning Using beta-Adrenoceptor Activation of the Dorsal Premammillary Nucleus as an Unconditioned Stimulus to Mimic Live Predator-Threat Exposure

In the present work, we sought to mimic the internal state changes in response to a predator threat by pharmacologically stimulating the brain circuit involved in mediating predator fear responses, and explored whether this stimulation would be a valuable unconditioned stimulus (US) in an olfactory fear conditioning paradigm (OFC). The dorsal premammillary nucleus (PMd) is a key brain structure in the neural processing of anti-predatory defensive behavior and has also been shown to mediate the acquisition and expression of anti-predatory contextual conditioning fear responses. Rats were conditioned by pairing the US, which was an intra-PMd microinjection of isoproterenol (ISO; beta-adrenoceptor agonist), with amyl acetate odor-the conditioned stimulus (CS). ISO (10 and 40 nmol) induced the acquisition of the OFC and the second-order association by activation of beta-1 receptors in the PMd. Furthermore, similar to what had been found for contextual conditioning to a predator threat, atenolol (beta-1 receptor antagonist) in the PMd also impaired the acquisition and expression of OFC promoted by ISO. Considering the strong glutamatergic projections from the PMd to the dorsal periaqueductal gray (dPAG), we tested how the glutamatergic blockade of the dPAG would interfere with the OFC induced by ISO. Accordingly, microinjections of NMDA receptor antagonist (AP5, 6 nmol) into the dPAG were able to block both the acquisition, and partially, the expression of the OFC. In conclusion, we have found that PMd beta-1 adrenergic stimulation is a good model to mimic predatory threat-induced internal state changes, and works as a US able to mobilize the same systems involved in the acquisition and expression of predator-related contextual conditioning. Neuropsychopharmacology (2011) 36, 926-939; doi:10.1038/npp.2010.231; published online 5 January 2011

Neuronal Expression of Cd36, Cd44, and Cd83 Antigen Transcripts Maps to Distinct and Specific Murine Brain Circuits

Cells recruited by the innate immune response rely on surface-expressed molecules in order to receive signals from the local environment and to perform phagocytosis, cell adhesion, and others processes linked to host defense. Hundreds of surface antigens designated through a cluster of differentiation (CD) number have been used to identify particular populations of leukocytes. Surprisingly, we verified that the genes that encode Cd36 and Cd83 are constitutively expressed in specific neuronal cells. For instance, Cd36 mRNA is expressed in some regions related to circuitry involved in pheromone responses and reproductive behavior. Cd44 expression, reanalyzed and detailed here, is associated with the laminar formation and midline thalamic nuclei in addition to striatum, extended amygdala, and a few hypothalamic, cortical, and hippocampal regions. A systemic immune challenge was able to increase Cd44 expression quickly in the area postrema and motor nucleus of the vagus but not in regions presenting expressive constitutive expression. In contrast to Cd36 and Cd44, Cd83 message was widely distributed from the olfactory bulb to the brain stem reticular formation, sparing the striatopallidum, olivary region, and cerebellum. Its pattern of expression nevertheless remained strongly associated with hypothalamic, thalamic, and hindbrain nuclei. Unlike the other transcripts, Cd83 mRNA was rapidly modulated by restraint stress. Our results indicate that these molecules might play a role in specific neural circuits and present functions other than those attributed to leukocyte biology. The data also suggest that these surface proteins, or their associated mRNA, could be used to label neurons in specific circuits/regions. J. Comp. Neurol. 517:906-924, 2009. (C) 2009 Wiley-Liss, Inc.

Forebrain projections to brainstem nuclei involved in the control of mandibular movements in rats

Mandibular movements occur through the triggering of trigeminal motoneurons. Aberrant movements by orofacial muscles are characteristic of orofacial motor disorders, such as nocturnal bruxism (clenching or grinding of the dentition during sleep). Previous studies have suggested that autonomic changes occur during bruxism episodes. Although it is known that emotional responses increase jaw movement, the brain pathways linking forebrain limbic nuclei and the trigeminal motor nucleus remain unclear. Here we show that neurons in the lateral hypothalamic area, in the central nucleus of the amygdala, and in the parasubthalamic nucleus, project to the trigeminal motor nucleus or to reticular regions around the motor nucleus (Regio h) and in the mesencephalic trigeminal nucleus. We observed orexin co-expression in neurons projecting from the lateral hypothalamic area to the trigeminal motor nucleus. In the central nucleus of the amygdala, neurons projecting to the trigeminal motor nucleus are innervated by corticotrophin-releasing factor immunoreactive fibers. We also observed that the mesencephalic trigeminal nucleus receives dense innervation from orexin and corticotrophin-releasing factor immunoreactive fibers. Therefore, forebrain nuclei related to autonomic control and stress responses might influence the activity of trigeminal motor neurons and consequently play a role in the physiopathology of nocturnal bruxism.

The Ventral Premammillary Nucleus Links Fasting-Induced Changes in Leptin Levels and Coordinated Luteinizing Hormone Secretion

Physiological conditions of low leptin levels like those observed during negative energy balance are usually characterized by the suppression of luteinizing hormone (LH) secretion and fertility. Leptin administration restores LH levels and reproductive function. Leptin action on LH secretion is thought to be mediated by the brain. However, the neuronal population that mediates this effect is still undefined. The hypothalamic ventral premammillary nucleus (PMV) neurons express a dense concentration of leptin receptors and project to brain areas related to reproductive control. Therefore, we hypothesized that the PMV is well located to mediate leptin action on LH secretion. To test our hypothesis, we performed bilateral excitotoxic lesions of the PMV in adult female rats. PMV-lesioned animals displayed a clear disruption of the estrous cycle, remaining in anestrus for 15-20 d. After apparent recovery of cyclicity, animals perfused in the afternoon of proestrus showed decreased Fos immunoreactivity in the anteroventral periventricular nucleus and in gonadotropin releasing hormone neurons. PMV-lesioned animals also displayed decreased estrogen and LH secretion on proestrus. Lesions caused no changes in mean food intake and body weight up to 7 weeks after surgery. We further tested the ability of leptin to induce LH secretion in PMV-lesioned fasted animals. We found that complete lesions of the PMV precluded leptin stimulation of LH secretion on fasting. Our findings demonstrate that the PMV is a key site linking changing levels of leptin and coordinated control of reproduction.

Discrete retinal input to the parabrachial complex of a new-world primate, the common marmoset (Callithrix jacchus)

Traditional retinal projections target three functionally complementary systems it) the brain of mammals: the primary visual system, the visuomotor integration systems and the circadian timing system. In recent years, studies in several animals have been conducted to investigate the retinal projections to these three systems, despite some evidence of additional targets. The aim of this study was to disclose a previously unknown connection between the retina and the parabrachial complex of the common marmoset, by means of the intraocular injection of cholera toxin Subunit b. A few labeled retinal fibers/terminals that are detected in the medial parabrachial portion of the marmoset brain show clear varicosities, Suggesting terminal fields. Although the possible role of these projections remains unknown, they may provide a modulation of the cholinergic parabrachial neurons which project to the thalamic dorsal lateral geniculate nucleus. (c) 2008 Elsevier Ireland Ltd. All rights reserved.

The periaqueductal gray and its potential role in maternal behavior inhibition in response to predatory threats

Animals faced with conflicting cues, such as predatory threat and a given rewarding stimulus, must make rapid decisions to engage in defensive versus other appetitive behaviors. The brain mechanisms mediating such responses are poorly understood. However, the periaqueductal gray (PAG) seems particularly suitable for accomplishing this task. The PAG is thought to have, at least, two distinct general roles on the organization of motivated responses, i.e., one on the execution of defensive and reproductive behaviors, and the other on the motivational drive underlying adaptive responses. We have presently examined how the PAG would be involved in mediating the behavioral choice between mutually incompatible behaviors, such as reproduction or defense, when dams are exposed to pups and cat odor. First, we established the behavioral protocol and observed that lactating rats, simultaneously exposed to pups and cat odor, inhibited maternal behavior and expressed clear defensive responses. We have further revealed that cat odor exposure up-regulated Fos expression in the dorsal PAG, and that NMDA cytotoxic lesions therein were able to restore maternal responses, and, at the same time, block defensive responsiveness to cat odor. Potential paths mediating the dorsal PAG influences on the inhibition of appetitive (i.e., retrieving behavior) and consummatory (i.e., nursing) maternal responses are discussed. Overall, we were able to confirm the dual role of the PAG, where, in the present case, the dorsal PAG, apart from organizing defensive responses, also appears to account for the behavioral inhibition of non-defensive responses. (C) 2010 Elsevier B.V. All rights reserved.