What's a brain: neuroanatomy and neurochemistry of anxiety disorders in dogs

This review deals with the neurocircuitry of fear and anxiety disorders, with the focus on neuroanatomy and neurochemistry. This knowledge is required to correctly diagnose and treat dogs with anxiety-related behavioral disorders. Research to date has shown the involvement of the frontal cortex, the amygdala, the thalamus and the hippocampus as core regions in regulating fear. Imbalances (hyper- or hypoactivation) in this fear circuitry can trigger inappropriate fear responses, i.e. anxiety disorders. Serotonin, dopamine and norepinephrine are the main neurotransmitters of emotion in the brain, but gamma-aminobutyric acid (GABA), glutamate, and the hypothalamic-pituitary-adrenal (HPA) axis producing glucocorticoids are also important in the neurochemistry of anxiety

Neurochemistry

Neurochemistry is a flourishing academic field that contributes to our understanding of molecular, cellular and medical neurobiology. As a scientific discipline, neurochemistry studies the role of chemicals that build the nervous system, it explores the function of neurons and glial cells in health and disease, it discovers aspects of cell metabolism and neurotransmission, and it reveals how degenerative processes are at work in the nervous system. Accordingly, this book contains chapters from a variety of topics that fall into the following broad sections: I. Neural Membranes and Intracellular Signaling, II. Neural Processing and Intercellular Signaling, III. Growth, Development and Differentiation, and IV. Neurodegenerative Diseases. The book presents comprehensive reviews in these different areas written by experts in their respective fields. Neurodegeneration and neuronal diseases are featured prominently and are a recurring theme throughout most chapters. This book will be a most valuable resource for neurochemists and other scientists alike. In addition, it will contribute to the training of current and future neurochemists and, hopefully, will lead us on the path to curing some of the biggest challenges in human health

How to run a brain bank. A report from the Austro-German brain bank

The sophisticated analysis of and growing information on the human brain requires that acquisition, dissection, storage and distribution of rare material are managed in a professional way. In this publication we present the concept and practice of our brain bank. Both brain tissue and information are handled by standardized procedures and flow in parallel from pathology to neuropathology and neurochemistry. Data concerning brain material are updated with clinical information gained by standardized procedures

Inactivation of presenilins causes pre-synaptic impairment prior to post-synaptic dysfunction

Synaptic dysfunction is widely thought to be a pathogenic precursor to neurodegeneration in Alzheimer’s disease (AD), and the extent of synaptic loss provides the best correlate for the severity of dementia in AD patients. Presenilins 1 and 2 are the major causative genes of early‐onset familial AD. Conditional inactivation of presenilins in the adult cerebral cortex results in synaptic dysfunction and memory impairment, followed by age‐dependent neurodegeneration. To characterize further the consequence of presenilin inactivation in the synapse, we evaluated the temporal development of pre‐synaptic and post‐synaptic deficits in the Schaeffer‐collateral pathway of presenilin conditional double knockout (PS cDKO) mice prior to onset of neurodegeneration. Following presenilin inactivation at 4 weeks, synaptic facilitation and probability of neurotransmitter release are impaired in PS cDKO mice at 5 weeks of age, whereas post‐synaptic NMDA receptor (NMDAR)‐mediated responses are normal at 5 weeks but impaired at 6 weeks of age. Long‐term potentiation induced by theta burst stimulation is also reduced in PS cDKO mice at 6 weeks of age. These results show that loss of presenilins results in pre‐synaptic deficits in short‐term plasticity and probability of neurotransmitter release prior to post‐synaptic NMDAR dysfunction, raising the possibility that presenilins may regulate post‐synaptic NMDAR function in part via a trans‐synaptic mechanism.This work was supported by the National Institute of Health NS041783 (to J.S.). We would like to thank Xiaoyan Zou and Huailong Zhao for technical assistance. (NS041783 - National Institute of Health)Published versio

Pituitary Adenylate Cyclase-Activating Polypeptide Orchestrates Neuronal Regulation Of The Astrocytic Glutamate-Releasing Mechanism System x\u3csub\u3ec\u3c/sub\u3e\u3csup\u3e−\u3c/sup\u3e

Glutamate signaling is achieved by an elaborate network involving neurons and astrocytes. Hence, it is critical to better understand how neurons and astrocytes interact to coordinate the cellular regulation of glutamate signaling. In these studies, we used rat cortical cell cultures to examine whether neurons or releasable neuronal factors were capable of regulating system xc-(Sxc), a glutamate-releasing mechanism that is expressed primarily by astrocytes and has been shown to regulate synaptic transmission. We found that astrocytes cultured with neurons or exposed to neuronal-conditioned media displayed significantly higher levels of Sxc activity. Next, we demonstrated that the pituitary adenylate cyclase-activating polypeptide (PACAP) may be a neuronal factor capable of regulating astrocytes. In support, we found that PACAP expression was restricted to neurons, and that PACAP receptors were expressed in astro-cytes. Interestingly, blockade of PACAP receptors in cultures comprised of astrocytes and neurons significantly decreased Sxc activity to the level observed in purified astrocytes, whereas application of PACAP to purified astrocytes increased Sxc activity to the level observed in cultures comprised of neurons and astrocytes. Collectively, these data reveal that neurons coordinate the actions of glutamate-related mechanisms expressed by astrocytes, such as Sxc, a process that likely involves PACAP

Differential detection of impact site versus rotational site injury by magnetic resonance imaging and microglial morphology in an unrestrained mild closed head injury model.

Seventy-five percent of all traumatic brain injuries are mild and do not cause readily visible abnormalities on routine medical imaging making it difficult to predict which individuals will develop unwanted clinical sequelae. Microglia are brain-resident macrophages and early responders to brain insults. Their activation is associated with changes in morphology or expression of phenotypic markers including P2Y12 and major histocompatibility complex class II. Using a murine model of unrestrained mild closed head injury (mCHI), we used microglia as reporters of acute brain injury at sites of impact versus sites experiencing rotational stress 24 h post-mCHI. Consistent with mild injury, a modest 20% reduction in P2Y12 expression was detected by quantitative real-time PCR (qPCR) analysis but only in the impacted region of the cortex. Furthermore, neither an influx of blood-derived immune cells nor changes in microglial expression of CD45, TREM1, TREM2, major histocompatibility complex class II or CD40 were detected. Using magnetic resonance imaging (MRI), small reductions in T2 weighted values were observed but only near the area of impact and without overt tissue damage (blood deposition, edema). Microglial morphology was quantified without cryosectioning artifacts using ScaleA(2) clarified brains from CX3CR1-green fluorescence protein (GFP) mice. The cortex rostral to the mCHI impact site receives greater rotational stress but neither MRI nor molecular markers of microglial activation showed significant changes from shams in this region. However, microglia in this rostral region did display signs of morphologic activation equivalent to that observed in severe CHI. Thus, mCHI-triggered rotational stress is sufficient to cause injuries undetectable by routine MRI that could result in altered microglial surveillance of brain homeostasis. Acute changes in microglial morphology reveal brain responses to unrestrained mild traumatic brain injury In areas subjected to rotational stress distant from impact site In the absence of detectable changes in standard molecular indicators of brain damage, inflammation or microglial activation. That might result in decreased surveillance of brain function and increased susceptibility to subsequent brain insults

GABA\u3csub\u3eB\u3c/sub\u3e Receptors Couple to Gα\u3csub\u3eq\u3c/sub\u3e to Mediate Increases in Voltage-Dependent Calcium Current During Development

Metabotropic GABAB receptors are known to modulate the activity of voltage-dependent calcium channels. Previously, we have shown that GABAB receptors couple to a non-Gi/o G-protein to enhance calcium influx through L-type calcium channels by activating protein kinase C in neonatal rat hippocampal neurons. In this study, the components of this signaling pathway were investigated further. Gαq was knocked down using morpholino oligonucleotides prior to examining GABAB-mediated enhancement of calcium influx. When Gαq G-proteins were eliminated using morpholino-mediated knockdown, the enhancing effects of the GABAB receptor agonist baclofen (10 μM) on calcium current or entry were eliminated. These data suggest that GABAB receptors couple to Gαq to regulate calcium influx. Confocal imaging analysis illustrating colocalization of GABAB receptors with Gαq supports this hypothesis. Furthermore, baclofen treatment caused translocation of PKCα (protein kinase C α) but not PKCβ or PKCε, suggesting that it is the α isoform of PKC that mediates calcium current enhancement. Inhibition of calcium/calmodulin-dependent kinase II did not affect the baclofen-mediated enhancement of calcium levels. In summary, activation of GABAB receptors during development leads to increased calcium in a subset of neurons through Gαq signaling and PKCα activation without the involvement of calcium/calmodulin-dependent kinase II

Lipid peroxidation is essential for α-synuclein-induced cell death.

Parkinson's disease is the second most common neurodegenerative disease and its pathogenesis is closely associated with oxidative stress. Deposition of aggregated α-synuclein (α-Syn) occurs in familial and sporadic forms of Parkinson's disease. Here, we studied the effect of oligomeric α-Syn on one of the major markers of oxidative stress, lipid peroxidation, in primary co-cultures of neurons and astrocytes. We found that oligomeric but not monomeric α-Syn significantly increases the rate of production of reactive oxygen species, subsequently inducing lipid peroxidation in both neurons and astrocytes. Pre-incubation of cells with isotope-reinforced polyunsaturated fatty acids (D-PUFAs) completely prevented the effect of oligomeric α-Syn on lipid peroxidation. Inhibition of lipid peroxidation with D-PUFAs further protected cells from cell death induced by oligomeric α-Syn. Thus, lipid peroxidation induced by misfolding of α-Syn may play an important role in the cellular mechanism of neuronal cell loss in Parkinson's disease. We have found that aggregated α-synuclein-induced production of reactive oxygen species (ROS) that subsequently stimulates lipid peroxidation and cell death in neurons and astrocytes. Specific inhibition of lipid peroxidation by incubation with reinforced polyunsaturated fatty acids (D-PUFAs) completely prevented the effect of α-synuclein on lipid peroxidation and cell death

A tight coupling between β\u3csub\u3e2\u3c/sub\u3eY97 and β\u3csub\u3e2\u3c/sub\u3eF200 of the GABA\u3csub\u3eA\u3c/sub\u3e receptor mediates GABA binding

The GABAA receptor is an oligopentameric chloride channel that is activated via conformation changes induced upon the binding of the endogenous ligand, GABA, to the extracellular inter-subunit interfaces. Although dozens of amino acid residues at the α/β interface have been implicated in ligand binding, the structural elements that mediate ligand binding and receptor activation are not yet fully described. In this study, double-mutant cycle analysis was employed to test for possible interactions between several arginines (α1R67, α1R120, α1R132, and β2R207) and two aromatic residues (β2Y97 and β2F200) that are present in the ligand-binding pocket and are known to influence GABA affinity. Our results show that neither α1R67 nor α1R120 is functionally coupled to either of the aromatics, whereas a moderate coupling exists between α1R132 and both aromatic residues. Significant functional coupling between β2R207 and both β2Y97 and β2F200 was found. Furthermore, we identified an even stronger coupling between the two aromatics, β2Y97 and β2F200, and for the first time provided direct evidence for the involvement of β2Y97 and β2F200 in GABA binding. As these residues are tightly linked, and mutation of either has similar, severe effects on GABA binding and receptor kinetics, we believe they form a single functional unit that may directly coordinate GABA

CCAAT/enhancer binding protein β expression is increased in the brain during HIV-1-infection and contributes to regulation of astrocyte tissue inhibitor of metalloproteinase-1

Human immunodeficiency virus (HIV)-1-associated neurocognitive disorders (HAND) associated with infection and activation of mononuclear phagocytes (MP) in the brain, occur late in disease. Infected/activated MP initiate neuroinflammation activating glial cells and ultimately disrupting neuronal function. Astrocytes secrete tissue inhibitor of metalloproteinase (TIMP)-1 in response to neural injury. Altered TIMP-1 levels are implicated in several CNS diseases. CCAAT enhancer-binding protein ß (C/EBPß), a transcription factor, is expressed in rodent brains in response to neuroinflammation, implicating it in Alzheimer’s, Parkinson’s, and HAND. Here, we report that C/EBPß mRNA levels are elevated and its isoforms differentially expressed in total brain tissue lysates of HIV-1-infected and HIV-1 encephalitis patients. In vitro, HAND-relevant stimuli additively induce C/EBPß nuclear expression in human astrocytes through 7 days of treatment. Over-expression of C/EBPß increases TIMP-1 promoter activity, mRNA, and protein levels in human astrocytes activated with interleukin-1ß. Knockdown of C/EBPß with siRNA decreases TIMP-1 mRNA and protein levels. These data suggest that C/EBPß isoforms are involved in complex regulation of astrocyte TIMP-1 production during HIV-1 infection; however, further studies are required to completely understand their role during disease progression