Avian Central Nervous System Research Articles

Fossil basicranium clarifies the origin of the avian central nervous system and inner ear.

Among terrestrial vertebrates, only crown birds (Neornithes) rival mammals in terms of relative brain size and behavioural complexity. Relatedly, the anatomy of the avian central nervous system and associated sensory structures, such as the vestibular system of the inner ear, are highly modified with respect to those of other extant reptile lineages. However, a dearth of three-dimensional Mesozoic fossils has limited our knowledge of the origins of the distinctive endocranial structures of crown birds. Traits such as an expanded, flexed brain, a ventral connection between the brain and spinal column, and a modified vestibular system have been regarded as exclusive to Neornithes. Here, we demonstrate all of these ‘advanced’ traits in an undistorted braincase from an Upper Cretaceous enantiornithine bonebed in southeastern Brazil. Our discovery suggests that these crown bird-like endocranial traits may have originated prior to the split between Enantiornithes and the more crownward portion of avian phylogeny over 140 Ma, while coexisting with a remarkably plesiomorphic cranial base and posterior palate region. Altogether, our results support the interpretation that the distinctive endocranial morphologies of crown birds and their Mesozoic relatives are affected by complex trade-offs between spatial constraints during development.

Central Nervous System Associated With Light Perception and Physiological Responses of Birds.

Environmental light that animal receives (i.e., photoperiod and light intensity) has recently been shown that it affects avian central nervous system for the physiological responses to the environment by up or downregulation of dopamine and serotonin activities, and this, in turn, affects the reproductive function and stress-related behavior of birds. In this study, the author speculated on the intriguing possibility that one of the proposed avian deep-brain photoreceptors (DBPs), i.e., melanopsin (Opn4), may play roles in the dual sensory-neurosecretory cells in the hypothalamus, midbrain, and brain stem for the behavior and physiological responses of birds by light. Specifically, the author has shown that the direct light perception of premammillary nucleus dopamine-melatonin (PMM DA-Mel) neurons is associated with the reproductive activation in birds. Although further research is required to establish the functional role of Opn4 in the ventral tegmental area (VTA), dorsal raphe nucleus, and caudal raphe nucleus in the light perception and physiological responses of birds, it is an exciting prospect because the previous results in birds support this hypothesis that Opn4 in the midbrain DA and serotonin neurons may play significant roles on the light-induced welfare of birds.

Purinergic Regulation of Food and Fat Intakes in Broiler’s Central Nervous System

BACKGROUND: Adenosine has many physiological roles in the brain, and in rodents, it changes food intake when applied centrally. OBJECTIVES: We investigated the effect of central injection of the purine molecule adenosine on both food and fat intakes in neonatal chicks. METHODS: In the first trial, various doses of adenosine (an endogenous P1 receptor agonist), and its synthetic antagonist CGS-15943, were injected intracerebroventricularly (ICV) to the chicks and the cumulative food intake was measured at definite time intervals. The second trial was similar to the first one, only the chicks were fed with a high-fat diet. RESULTS: Adenosine did not affect food or fat intake. Food consumption was increased 30 min after injection of CGS-15943. CGS-15943 also increased fat intake in chicks fed a high-fat diet. CONCLUSIONS: The present study suggests that in the avian central nervous system, P1 receptors are entailed in the regulation of food and fat intake in an antagonistic manner.

Analysis of the source of aggressiveness in gamecocks

Although the fighting behaviour in gamecocks has evolved because of artificial selection, it is unknown whether the selection for aggressiveness affects neurotransmitter levels in the avian central nervous system. We sought to identify the source and origin of this trait. We collected the brain samples from 6 female Shamo gamecocks and 5 Shaver Brown chickens (control; bred for egg production). The midbrain levels of norepinephrine (NE) were significantly higher in Shamo gamecocks (P = 0.0087) than in the controls. Moreover, alleles encoding adrenergic receptors differed between the breeds in terms of response to NE. Gene mutations specific to Shamo and potentially associated with fighting behaviour were in sites T440N of ADRα1D; V296I of ADRα2A; and T44I, Q232R, and T277M of ADRβ2. The evolutionary analysis indicated that the ADRβ2 (T44I and Q232R) mutations were heritable in all Galliformes, whereas the T440N mutation of ADRα1D and V296I mutations of ADRα2A were unique to Shamo and originated by artificial selection. A high NE level may confer a selective advantage by enabling gamecocks to be aggressive and pain tolerant. Therefore, the strong fighting behaviour of Shamo has resulted from a combination of naturally inherited and mutant genes derived by artificial selection.

Host CARD11 Inhibits Newcastle Disease Virus Replication by Suppressing Viral Polymerase Activity in Neurons.

Host factors play multiple essential roles in the replication and pathogenesis of mammalian neurotropic viruses. However, the cellular proteins of the central nervous system (CNS) involved in avian neurotropic virus infection have not been completely elucidated. Here, we employed a gene microarray to identify caspase recruitment domain-containing protein 11 (CARD11), a lymphoma-associated scaffold protein presenting brain-specific upregulated expression in a virulent neurotropic Newcastle disease virus (NDV)-infected natural host. Chicken primary neuronal cells infected with NDV appeared slightly syncytial and died quickly. CARD11 overexpression inhibited viral replication and delayed cytopathic effects; conversely, depletion of CARD11 enhanced viral replication and cytopathic effects in chicken primary neuronal cells. The inhibition of viral replication by CARD11 could not be blocked with CARD11-Bcl10-MALT1 (CBM) signalosome and NF-κB signaling inhibitors. CARD11 was found to interact directly with the viral phosphoprotein (P) through its CC1 domain and the X domain of P; this X domain also mediated the interaction between P and the viral large polymerase protein (L). The CARD11 CC1 domain and L competitively bound to P via the X domain that hindered the P-L interaction of the viral ribonucleoprotein (RNP) complex, resulting in a reduction of viral polymerase activity in a minigenome assay and inhibition of viral replication. Animal experiments further revealed that CARD11 contributed to viral replication inhibition and neuropathology in infected chicken brains. Taken together, our findings identify CARD11 as a brain-specific antiviral factor of NDV infection in avian species.IMPORTANCE Newcastle disease virus (NDV) substantially impacts the poultry industry worldwide and causes viral encephalitis and neurological disorders leading to brain damage, paralysis, and death. The mechanism of interaction between this neurotropic virus and the avian central nervous system (CNS) is largely unknown. Here, we report that host protein CARD11 presented brain-specific upregulated expression that inhibited NDV replication, which was not due to CARD11-Bcl10-MALT1 (CBM) complex-triggered activation of its downstream signaling pathways. The inhibitory mechanism of viral replication is through the CARD11 CC1 domain, and the viral large polymerase protein (L) competitively interacts with the X domain of the viral phosphoprotein (P), which hampers the P-L interaction, suppressing the viral polymerase activity and viral replication. An in vivo study indicated that CARD11 alleviated neuropathological lesions and reduced viral replication in chicken brains. These results provide insight into the interaction between NDV infection and the host defense in the CNS and a potential antiviral target for viral neural diseases.

3.0 Tesla magnetic resonance imaging anatomy of the central nervous system, eye, and inner ear in birds of prey.

Despite the increasing interest in the clinical neurology of birds, little is known about the magnetic resonance imaging (MRI) appearance of the avian central nervous system, eye, and inner ear. The objective of this cadaveric study was to document the MRI anatomic features of the aforementioned structures using a high-resolution 3.0 Tesla MRI system. The final study group consisted of 13 cadavers of the diurnal birds of prey belonging to six species. Images were acquired in sagittal, dorsal, and transverse planes using T1-weighted and T2-weighted turbo spin echo sequences. A necropsy with macroscopic analysis of the brain and spinal cord was performed on all cadavers. Microscopic examination of the brain was performed on one cadaver of each species; the spinal cord was examined in three subjects. Anatomic structures were identified on the magnetic resonance images based on histologic slices and available literature. Very good resolution of anatomic detail was obtained. The olfactory bulbs; cerebral hemispheres; diencephalon; optic lobe; cerebellum; pons; ventricular system; optic, trigeminal, and facial nerves; pineal and pituitary glands; as well as the semicircular canals of the inner ear were identified. Exquisite detail was achieved on the ocular structures. In the spinal cord, the gray and white matter differentiation and the glycogen body were identified. This study establishes normal MRI anatomy of the central nervous system, eye, and inner ear of the birds of prey; and may be used as a reference in the assessment of neurologic disorders or visual impairment in this group of birds.

In Vivo and In Vitro Knockdown Approaches in the Avian Embryo as a Means to Study Semaphorin Signaling.

A combination of both in vivo and in vitro techniques is invaluable for studying semaphorin signaling in the avian central nervous system. Here we describe how both types of approaches can be used to compliment each other in order to unravel the role that semaphorins play during embryonic development and elucidate the functional consequences of semaphorin knockdown using RNA interference vectors. We describe and discuss specifically the use of in ovo electroporation and primary oculomotor neuron culture to identify the role of semaphorins in oculomotor neuron migration and assess functional consequences of semaphorin disruption in this system.

Recent Research on the Centrifugal Visual System in Mammalian Species

Ample evidence indicates that both retinofugal (classical visual and the retino-hypothalamic pathways) and retinopetal connections (centrifugal visual system) are found between the eye and the central nervous system. More than hundred years ago Ramon Y Cajal and Dogiel, whose names are very well known by neuro-anatomists, described the termination pattern of the fibers deriving from the avian central nervous system. However, the location of nerve cell bodies was not known at that time. In the last century many data accumulated about these neurons not only in lower vertebrates but in mammals as well. The structures where the neurons give rise to the centrifugal visual fibres in mammals are the following: reticular formation and raphe nuclei of the midbrain, superior colliculus, pretectum, gray matter of the midbrain, dentate gyrus, CA1 and CA3 regions of the hippocampus, olfactory tubercle, habenula, indusium griseum, hypothalamic supraoptic, Para ventricular and arcuate nuclei, and the lateral hypothalamus. The centrifugal visual fibers enter the optic nerve layer, then reach the inner plexiform layer and terminate in the inner nulear layer of the retina in the vicinity of the amacrine cells. A series of neuropeptides and neurotransmitters was described in the origin of the centrifugal visual system. These are the followings: luteinizing hormone releasing hormone, pituitary adenylate cyclase activating polypeptide, vasoactive intestinal polypeptide, serotonin, histamine and leu-enkephalin. Several hypotheses arose on the function of this system. Centrifugal visual system arising from the histaminergic mammillary neurons modifies the sleep/wake cycle. Hallucinogenic drugs through the limbic system may cause disturbance of visual function and result in seeing visual hallucinations or distorted images.

A Cholesterol Tag at the N Terminus of the Relatively Broad-Spectrum Fusion Inhibitory Peptide Targets an Earlier Stage of Fusion Glycoprotein Activation and Increases the Peptide's Antiviral Potency In Vivo

In previous work, we designed peptides that showed potent inhibition of Newcastle disease virus (NDV) and infectious bronchitis virus (IBV) infections in chicken embryos. In this study, we demonstrate that peptides modified with cholesterol or 3 U of polyethylene glycol (PEG3) conjugated to the peptides' N termini showed even more promising antiviral activities when tested in animal models. Both cholesterol- and cholesterol-PEG3-tagged peptides were able to protect chicken embryos from infection with different serotypes of NDV and IBV when administered 12 h prior to virus inoculation. In comparison, the untagged peptides required intervention closer to the time of viral inoculation to achieve a similar level of protection. Intramuscular injection of cholesterol-tagged peptide at 1.6 mg/kg 1 day before virus infection and then three times at 3-day intervals after viral inoculation protected 70% of the chickens from NDV infection. We further demonstrate that the cholesterol-tagged peptide has an in vivo half-life greater than that of untagged peptides. It also has the potential to cross the blood-brain barrier to enter the avian central nervous system (CNS). Finally, we show that the cholesterol-tagged peptide could play a role before the viral fusion peptide's insertion into the host cell and thereby target an earlier stage of fusion glycoprotein activation. Our findings are of importance for the further development of antivirals with broad-spectrum protective effects.

Absence of post‐lesion reactive gliosis in elasmobranchs and turtles and its bearing on the evolution of astroglia

In the mature mammalian and avian central nervous systems, neuronal destructions are followed by reactive gliosis, but data on other vertebrates are rather controversial. Mammals and birds belong to different amniote groups (Synapsida and Diapsida, respectively), but exhibit common general features in their glial architecture, mainly the predominance of astrocytes. Two vertebrate groups seem to be in special positions of glial evolution: turtles (Testudiniformes) and skates and rays (Batoidea). The purely ependymoglial system of turtles seems to be the simplest one among the extant amniotes. In skates and rays, true astrocytes are preponderant glial elements, in contrast to the other "anamniotes" (and even to reptiles). We investigated stab wounds by the immunohistochemical detection of GFAP in turtles (Trachemys-formerly Pseudemys-scripta elegans), a skate (Raja clavata) and rays (Dasyatis akajei and Torpedo marmorata). Sharks (Scyliorhinus canicula) as ependymoglia-predominated chondrichthyans, and-for positive controls-rats were also studied. In the elasmobranchs, other astroglial markers: glutamine synthetase and S100 protein were also applied. Neither turtles nor elasmobranchs presented considerable astroglial reactions. Critically surveying the former reports on different vertebrates, these results complete the picture that typical post-lesion reactive gliosis is confined to mammals and birds. Analysis of the astroglial systems from phylogenetic perspective suggests that the capability of forming glial demarcation and scar formation evolved independently in mammals and birds. Predominance of astrocytes is a necessary condition but not sufficient for reactive gliosis. The intense glial reactivity of mammals and birds may be attributed to their complex cerebralization.

Immunohistochemical localization of vesicular glutamate transporter 2 (vGluT2) in the central nervous system of the pigeon (Columba livia)

Glutamatergic neurons are distributed widely in the telencephalic pallium of birds, but their targets are unknown. In the present study, a polyclonal antibody was produced against pigeon vesicular glutamate transporter 2 (vGluT2) and was used for Western blot and immunohistochemistry to detect projection targets of glutamatergic neurons in the pigeon central nervous system. The molecular weight of vGluT2 was measured at 65 kDa. vGluT2 immunoreactivity was observed in neuropil, but not in neuronal cell bodies or glia. Immunoreactive neuropil generally appeared homogeneous, but fine granules or puncta were found in many areas or nuclei. The telencephalon showed strong immunoreactivity, except for the globus pallidus. In particular, the mesopallium and hippocampal formation revealed the most intense immunostaining. In the diencephalon, vGluT2 immunoreactivity was intense in the dorsal thalamus and hypothalamus. In the midbrain, strong immunostaining was seen in the periaqueductal gray, the dorsal part of the lateral mesencephalic nucleus, and the isthmo-optic nucleus. The optic tectum showed moderate immunoreactivity. In the cerebellar cortex, glomeruli in the granular layer were intensely immunoreactive, and the molecular layer showed intensely homogeneous immunostaining. In the caudal brainstem, the cochlear magnocellular and angular nuclei showed strongly immunoreactive puncta around neuronal cell bodies. In the spinal cord, the dorsal horn revealed moderate immunoreactivity and the marginal nucleus was strongly immunoreactive. Ultrastructural observations revealed that vGluT2 immunoreactivity is localized in asymmetric, presynaptic terminals. The present results indicate an extensive distribution of glutamatergic projections and circuits in the avian central nervous system.

09-P055 Origin and characterization of microglial cells in the avian central nervous system

09-P055 Origin and characterization of microglial cells in the avian central nervous system

Origin and characterization of microglial cells in the avian central nervous system

Event Abstract Back to Event Origin and characterization of microglial cells in the avian central nervous system Dávid Molnár1*, Imre Olah1 and Nándor Nagy1 1 Department of Human Morphology and Developmental Biology ,Semmelweis University, Hungary The origin of the microglial cells in the central nervous system and in the pineal gland is still a matter of debate. Besides the neuroepithelial origin recently the mesodermal or hemopoietic origin is generally accepted but not experimentally proved. The aim of our studies was to characterize immunocytochemically the microglial cells and to provide experimental evidence for their origin in the central nervous system. Different cell specific markers have been used for immunocytochemical characterization of the microglial cells: hemopoietic; B lymphocyte; T lymphocyte; macrophage; MHC class II, cell adhesion and avian dendritic cell. In the pineal parenchyma and over the CNS a poorly and highly ramified CD45+ hemopoietic cells can be distinguished. The former one expressed macrophage markers while other was positive for Bu1 (B cell specific antibody), CD44 and Ricinus communis agglutinin I (RCA I), a lectin specific for avian microglial cells. The immunocytochemical characterization of the CD45+/Bu1+/CD44+/RCA I+ cells strongly suggested their hemopoietic origin and expression of MHC class II antigen makes them capable for antigen presentation. To clarify the origin of microglial cells chick-quail chimera has been made: quail pineal gland from 10 days old embryo was isolated and transplanted either into the coelomic cavity of a 3 days old chicken embryo or onto the chorioallantioic membrane. Hemopoietic cells from the chick embryo migrated to and colonized the grafted pineal gland and differentiated into CD45+/Bu1+/MHC II+/CD44+/RCA1+ microglia cells. Conference: 12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009. Presentation Type: Poster Presentation Topic: Developmental neurobiology and subcortical functions Citation: Molnár D, Olah I and Nagy N (2009). Origin and characterization of microglial cells in the avian central nervous system. Front. Syst. Neurosci. Conference Abstract: 12th Meeting of the Hungarian Neuroscience Society. doi: 10.3389/conf.neuro.01.2009.04.067 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Mar 2009; Published Online: 02 Mar 2009. * Correspondence: Dávid Molnár, Department of Human Morphology and Developmental Biology ,Semmelweis University, Budapest, Hungary, chewyd@freemail.hu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Dávid Molnár Imre Olah Nándor Nagy Google Dávid Molnár Imre Olah Nándor Nagy Google Scholar Dávid Molnár Imre Olah Nándor Nagy PubMed Dávid Molnár Imre Olah Nándor Nagy Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Development of a Dot Blot Assay for the Rapid Detection of Central Nervous System Tissue on Meat and Contact Surfaces

As a potential transmitter of bovine spongiform encephalopathy (BSE), tissue from bovine central nervous system (CNS) is not accepted in meat and meat products. Western blot analysis of the CNS marker myelin proteolipid protein (PLP) detects CNS contamination selectively and sensitively. In this study, a rapid dot blot assay using an anti-PLP antibody was developed to screen CNS contamination of meat and contact surfaces. The detection limit was 0.01% bovine brain in minced bovine muscle. When applied to a swab test, down to 0.5 mg of CNS tissue on meat or other surfaces was detectable. Other offal tissues or peripheral nerves did not interfere with the assay. The test allows a differentiation between mammalian and avian CNS but not among mammalian species. The swab test was applied immediately after slaughtering at several areas of the bovine head. CNS was not detectable at any region which may enter the food chain.

Phosphorylation of neurofibromin by PKC is a possible molecular switch in EGF receptor signaling in neural cells

Children with neurofibromatosis (NF1) typically develop central nervous system (CNS) abnormalities, including aberrant proliferation of astrocytes and formation of benign astrocytomas. The NF1 gene encodes neurofibromin, a Ras-GAP, highly expressed in developing neural cells; the mechanism of regulation of neurofibromin as a Ras-GAP, remains however unknown. We now show that, in response to EGF, neurofibromin is in vivo phosphorylated on serine residues by PKC-alpha, in human, rat, and avian CNS cells and cell lines. EGF-induced PKC phosphorylation was prominent in the cysteine/serine-rich domain (CSRD) of neurofibromin, which lies in the N-terminus and upstream of the Ras-GAP domain (GRD), and this modification significantly increased the association of neurofibromin with actin in co-immunoprecipitations. In addition, we show that Ras activation in response to EGF was significantly lowered when C62B cells overexpressed a construct encoding both CSRD + GRD. Moreover, when PKC-alpha was downregulated, the Ras-GAP activity of CSRD + GRD was significantly diminished, whereas overexpressed GRD alone acted as a weaker GAP and in a PKC-independent manner. Most importantly, functional Ras inhibition and EGF signaling shifts were established at the single cell level in C6-derived cell lines stably overexpressing CSRD + GRD, when transient co-overexpression of Ras and PKC-depletion prior to stimulation with EGF-induced mitosis. Taken together, these data provide the first evidence of a functional, allosteric regulation of GRD by CSRD, which requires neurofibromin phosphorylation by PKC and association with the actin cytoskeleton. Our data may suggest a novel mechanism for regulating biological responses to EGF and provide a new aspect for the understanding of the aberrant proliferation seen in the CNS of children with NF1.

Distribution of NADPH diaphorase-containing neurons in the pigeon central nervous system

The aim of the present study was to determine the distribution of nitric oxide-synthesizing neurons in the pigeon brain and spinal cord. Tissue sections were stained for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d). In the telencephalon, intensely stained neurons with dendrites extending distally were seen in most regions. The ectostriatum was characterized by intensely and diffusely stained neuropil. In the diencephalon, intensely positive neurons were seen in the lateral hypothalamic region and lateral mammillary nucleus. In the mesencephalon, intensely stained, multipolar neurons were abundantly scattered in the central gray, nucleus intercollicularis, reticular formation, nucleus tegmenti pedunculo-pontinus, pars compacta, area ventralis of Tsai, and ansa lenticularis. In the rhombencephalon, positively-stained neurons were found in the pontine nuclei and reticular formation. The cerebellar cortex, except for Purkinje cells, was a preferential region for NADPH-d activity. Positive end-bulbs made contact on somata in the nucleus magnocellularis cochlearis. In the spinal cord, NADPH-d positive neurons were seen in layer II and the marginal nucleus. Our results demonstrated that the distribution of NADPH-d-containing neurons in the pigeon brain and spinal cord is more complex than in other avian species. Our findings indicate that NADPH-d-containing neurons are present in several sensory pathways, including olfactory, visual, auditory, and somatosensory tracts, although some nuclei in each system did not show NADPH-d activity. The wide distribution of NADPH-d activity in the pigeon CNS suggests that nitric oxide modulates sensory transmission in avian central nervous system.

Effects of pituitary adenylate cyclase-activating polypeptide (PACAP) on cyclic AMP formation in the duck and goose brain

Two molecular forms of pituitary adenylate cyclase-activating polypeptide (PACAP), i.e., PACAP27 and PACAP38 (0.0001-1 μM), as well as vasoactive intestinal polypeptide (VIP; 0.1-3 μM), have been studied for their effects on cyclic AMP formation in the hypothalamus and cerebral cortex of duck and goose. All three peptides concentration-dependently stimulated cyclic AMP production in the tested brain regions of 2-3-weeks-old (young) ducks, with VIP showing at least one order of magnitude weaker activity than PACAP. This characteristics suggests the existence in the duck's brain of adenylyl cyclase-linked PAC1 receptors. Both forms of PACAP also stimulated the nucleotide formation in the cerebral cortex and hypothalamus of 5-6-months-old (adult) ducks or geese grown under natural environment. The peptides-evoked effects in adult and young ducks were comparable, and clearly greater than those found in adult geese. The present data extend our recent observations made on chicks, and suggest PACAP to be a potent stimulator of the cyclic AMP generation in the avian central nervous system.

Modulatory action of zinc on GABAA receptor complex during avian CNS development

In the present work, we studied the effect of zinc on GABA(A) receptor complex at three developmental stages of chick optic lobe (embryonic day 14, post-hatching day 1, and adulthood), in order to investigate the role of this cation in central nervous system (CNS) functional maturation. It was demonstrated that zinc exerts an inhibitory modulation of both GABA binding and GABA-gated chloride flux in a concentration-dependent manner with maximal effects at 100 microM zinc concentration. Maximal inhibition was higher at the embryonic stage and declined thereafter, disclosing minimal values at the adult stage. The effect of zinc on saturation GABA binding experiments performed at embryonic day 14 demonstrated that the cation decreased the maximal number of binding sites (B(max)) from 7. 53 +/- 1.06 pmol/mg protein to 4.63 +/- 0.53 pmol/mg protein, in the absence and presence of 100 microM zinc, respectively, while the dissociation constant (K(d)) remained unchanged. Analysis of the GABA concentration-effect curve at the embryonic stage revealed that the addition of 100 microM zinc decreased E(max) values for GABA stimulation of chloride uptake from 26.46 +/- 2.64% to 16.40 +/- 1. 96%, while EC(50) values were unaffected. In conclusion, our results suggest that zinc acts as a non-competitive inhibitor of both GABA binding and GABA responses during avian CNS development, with its effect inversely related to age.

Modulatory action of zinc on GABAA receptor complex during avian CNS development

In the present work, we studied the effect of zinc on GABAA receptor complex at three developmental stages of chick optic lobe (embryonic day 14, post-hatching day 1, and adulthood), in order to investigate the role of this cation in central nervous system (CNS) functional maturation. It was demonstrated that zinc exerts an inhibitory modulation of both GABA binding and GABA-gated chloride flux in a concentration-dependent manner with maximal effects at 100 μM zinc concentration. Maximal inhibition was higher at the embryonic stage and declined thereafter, disclosing minimal values at the adult stage. The effect of zinc on saturation GABA binding experiments performed at embryonic day 14 demonstrated that the cation decreased the maximal number of binding sites (Bmax) from 7.53 ± 1.06 pmol/mg protein to 4.63 ± 0.53 pmol/mg protein, in the absence and presence of 100 μM zinc, respectively, while the dissociation constant (Kd) remained unchanged. Analysis of the GABA concentration-effect curve at the embryonic stage revealed that the addition of 100 μM zinc decreased Emax values for GABA stimulation of chloride uptake from 26.46 ± 2.64% to 16.40 ± 1.96%, while EC50 values were unaffected. In conclusion, our results suggest that zinc acts as a non-competitive inhibitor of both GABA binding and GABA responses during avian CNS development, with its effect inversely related to age. J. Neurosci. Res. 57:536–540, 1999. © 1999 Wiley-Liss, Inc.

Agrin in Alzheimer's disease: altered solubility and abnormal distribution within microvasculature and brain parenchyma.

Agrin is a heparan sulfate proteoglycan that is widely expressed in neurons and microvascular basal lamina in the rodent and avian central nervous system. Agrin induces the differentiation of nerve-muscle synapses, but its function in either normal or diseased brains is not known. Alzheimer's disease (AD) is characterized by loss of synapses, changes in microvascular architecture, and formation of neurofibrillary tangles and senile plaques. Here we have asked whether AD causes changes in the distribution and biochemical properties of agrin. Immunostaining of normal, aged human central nervous system revealed that agrin is expressed in neurons in multiple brain areas. Robust agrin immunoreactivity was observed uniformly in the microvascular basal lamina. In AD brains, agrin is highly concentrated in both diffuse and neuritic plaques as well as neurofibrillary tangles; neuronal expression of agrin also was observed. Furthermore, patients with AD had microvascular alterations characterized by thinning and fragmentation of the basal lamina. Detergent extraction and Western blotting showed that virtually all the agrin in normal brain is soluble in 1% SDS. In contrast, a large fraction of the agrin in AD brains is insoluble under these conditions, suggesting that it is tightly associated with beta-amyloid. Together, these data indicate that the agrin abnormalities observed in AD are closely linked to beta-amyloid deposition. These observations suggest that altered agrin expression in the microvasculature and the brain parenchyma contribute to the pathogenesis of AD.