Spiny Cells Research Articles

Cell-type-specific resonances shape the responses of striatal neurons to synaptic input.

Neurons respond to synaptic inputs in cell-type-specific ways. Each neuron type may thus respond uniquely to shared patterns of synaptic input. We applied statistically identical barrages of artificial synaptic inputs to four striatal cell types to assess differences in their responses to a realistic input pattern. Each interneuron type fired in phase with a specific input-frequency component. The fast-spiking interneuron fired in relation to the gamma-band (and higher) frequencies, the low-threshold spike interneuron to the beta-band frequencies, and the cholinergic neurons to the delta-band frequencies. Low-threshold spiking and cholinergic interneurons showed input impedance resonances at frequencies matching their spiking resonances. Fast-spiking interneurons showed resonance of input impedance but at lower than gamma frequencies. The spiny projection neuron's frequency preference did not have a fixed frequency but instead tracked its own firing rate. Spiny cells showed no input impedance resonance. Striatal interneurons are each tuned to a specific frequency band corresponding to the major frequency components of local field potentials. Their influence in the circuit may fluctuate along with the contribution of that frequency band to the input. In contrast, spiny neurons may tune to any of the frequency bands by a change in firing rate.

Inhibitory synapse formation in a co-culture model incorporating GABAergic medium spiny neurons and HEK293 cells stably expressing GABAA receptors.

Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA (γ-aminobutyric acid) is the predominant inhibitory neurotransmitter in the brain. It is released from the presynaptic terminals of inhibitory neurons within highly specialized intercellular junctions known as synapses, where it binds to GABAA receptors (GABAARs) present at the plasma membrane of the synapse-receiving, postsynaptic neurons. Activation of these GABA-gated ion channels leads to influx of chloride resulting in postsynaptic potential changes that decrease the probability that these neurons will generate action potentials. During development, diverse types of inhibitory neurons with distinct morphological, electrophysiological and neurochemical characteristics have the ability to recognize their target neurons and form synapses which incorporate specific GABAARs subtypes. This principle of selective innervation of neuronal targets raises the question as to how the appropriate synaptic partners identify each other. To elucidate the underlying molecular mechanisms, a novel in vitro co-culture model system was established, in which medium spiny GABAergic neurons, a highly homogenous population of neurons isolated from the embryonic striatum, were cultured with stably transfected HEK293 cell lines that express different GABAAR subtypes. Synapses form rapidly, efficiently and selectively in this system, and are easily accessible for quantification. Our results indicate that various GABAAR subtypes differ in their ability to promote synapse formation, suggesting that this reduced in vitro model system can be used to reproduce, at least in part, the in vivo conditions required for the recognition of the appropriate synaptic partners and formation of specific synapses. Here the protocols for culturing the medium spiny neurons and generating HEK293 cells lines expressing GABAARs are first described, followed by detailed instructions on how to combine these two cell types in co-culture and analyze the formation of synaptic contacts.

Inhibitory Synapse Formation in a Co-culture Model Incorporating GABAergic Medium Spiny Neurons and HEK293 Cells Stably Expressing GABA<sub>A</sub> Receptors

Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA (γ-aminobutyric acid) is the predominant inhibitory neurotransmitter in the brain. It is released from the presynaptic terminals of inhibitory neurons within highly specialized intercellular junctions known as synapses, where it binds to GABAA receptors (GABAARs) present at the plasma membrane of the synapse-receiving, postsynaptic neurons. Activation of these GABA-gated ion channels leads to influx of chloride resulting in postsynaptic potential changes that decrease the probability that these neurons will generate action potentials. During development, diverse types of inhibitory neurons with distinct morphological, electrophysiological and neurochemical characteristics have the ability to recognize their target neurons and form synapses which incorporate specific GABAARs subtypes. This principle of selective innervation of neuronal targets raises the question as to how the appropriate synaptic partners identify each other. To elucidate the underlying molecular mechanisms, a novel in vitro co-culture model system was established, in which medium spiny GABAergic neurons, a highly homogenous population of neurons isolated from the embryonic striatum, were cultured with stably transfected HEK293 cell lines that express different GABAAR subtypes. Synapses form rapidly, efficiently and selectively in this system, and are easily accessible for quantification. Our results indicate that various GABAAR subtypes differ in their ability to promote synapse formation, suggesting that this reduced in vitro model system can be used to reproduce, at least in part, the in vivo conditions required for the recognition of the appropriate synaptic partners and formation of specific synapses. Here the protocols for culturing the medium spiny neurons and generating HEK293 cells lines expressing GABAARs are first described, followed by detailed instructions on how to combine these two cell types in co-culture and analyze the formation of synaptic contacts.

The reasons for the preferable use of A2A receptor antagonists for improvement of locomotor activity and learning

Previously, we hypothesized that dopamine, as well as antagonists of muscarinic and adenosine receptors, enhances locomotor activity due to modulation of the efficacy of cortical inputs to striatal spiny cells and synergistic disinhibition of neurons of the thalamus and cortex via the direct and indirect pathways in the basal ganglia [Silkis, 2001]. It was shown that the occurrence of a pause in the responses of cholinergic interneurons of the striatum to sensory stimuli promotes this disinhibition due to weakening of the activation of muscarinic receptors on spiny cells. We proposed a hypothetical mechanism for the appearance of this pause, which includes afferent inhibition and activation of D2 receptors [Silkis, 2004]. Current studies support this mechanism. In this study, we propose that a decrease in the activity of cholinergic neurons results in the enhancement of the excitation of spiny cells by cortical afferents due to weakening of their inhibition by inhibitory striatal interneurons that express nicotinic receptors. We put forward a hypothesis that the use of antagonists of A2A receptors is preferable for the improvement of locomotor activity, treatment of Parkinson’s disease, learning, and the choice of actions that results in better reinforcement because only these antagonists promote the occurrence of a pause in the responses to cholinergic interneurons and a decrease in their activity. Due to the same reason the treatment of mental diseases by antagonists of D2 receptors should additionally include antagonists of A2A receptors. Although antagonists of A1 receptors promote the disinhibition of neurons of the thalamus and cortex via the direct pathway in the basal ganglia, their use is undesirable because it may lead to an increase in the activity of cholinergic interneurons and prevent a pause in their responses. In addition, after systemic administration of antagonists of A2A receptors, they should predominantly influence the functioning of the striatum, where they are predominantly located, whereas A1 receptors are widely expressed in the brain and systemic administration of their antagonists may result in unpredictable side effects.

Procedural-based category learning in patients with Parkinson's disease: impact of category number and category continuity

Previously we found that Parkinson's disease (PD) patients are impaired in procedural-based category learning when category membership is defined by a nonlinear relationship between stimulus dimensions, but these same patients are normal when the rule is defined by a linear relationship (Maddox and Filoteo, 2001; Filoteo et al., 2005a,b). We suggested that PD patients' impairment was due to a deficit in recruiting “striatal units” to represent complex nonlinear rules. In the present study, we further examined the nature of PD patients' procedural-based deficit in two experiments designed to examine the impact of (1) the number of categories, and (2) category discontinuity on learning. Results indicated that PD patients were impaired only under discontinuous category conditions but were normal when the number of categories was increased from two to four. The lack of impairment in the four-category condition suggests normal integrity of striatal medium spiny cells involved in procedural-based category learning. In contrast, and consistent with our previous observation of a nonlinear deficit, the finding that PD patients were impaired in the discontinuous condition suggests that these patients are impaired when they have to associate perceptually distinct exemplars with the same category. Theoretically, this deficit might be related to dysfunctional communication among medium spiny neurons within the striatum, particularly given that these are cholinergic neurons and a cholinergic deficiency could underlie some of PD patients' cognitive impairment.

First Published Report of Rust on White Alder Caused by Melampsoridium hiratsukanum in the United States.

White alder (Alnus rhombifolia) is a fast-growing tree native to the western United States and is planted frequently in landscapes. In September 2010, mature leaves of white alder with small, orange-yellow pustules were collected in a commercial nursery in Santa Cruz County, CA. Approximately 25 white alder trees were affected. Collected leaves were sent to the California Department of Food and Agriculture Plant Pest Diagnostics Laboratory. Young uredinial pustules were bullate, with urediniospores emerging from a single pore in the pustule. Spiny cells lined the ostiole. With age, pustules broke open to release more spores. Urediniospores were obovate to oval and measured from 14 to 20 × 27 to 41 μm (17.1 × 32.2 μm average, n = 62). Spores were uniformly echinulate and contained a nearly hyaline cell wall measuring from 1 to 2 μm (1.5 μm average) in thickness. A portion of the 28S ribosomal subunit (GenBank Accession No. KC313888) and the internal transcribed spacer regions (KC313889) were amplified and sequenced from DNA extracted from urediniospores using primers LR6 and rust2inv (1) and ITS1-F and ITS4-B (2), respectively. Our ITS sequence had 99% identity to GenBank accession EF564164, Melampsoridium hiratsukanum. In September 2011, white alder leaves with similar symptoms were collected from a commercial nursery in Santa Barbara County, CA. The spore morphology matched the white alder sample previously collected in Santa Cruz County, CA, in 2010. At that time, pathogenicity assays were conducted on three 1-year-old, 61-cm white alder trees planted in 3.8-liter pots. Six detached leaves with visible rust pustules were rubbed gently onto both the apical and distal side of moistened leaves of the healthy alders. Each infected leaf was used to inoculate a total of 6 to 10 healthy leaves by rubbing two leaves per tree before moving to the next tree. Leaves on three additional white alder trees were rubbed with healthy leaves as controls. Trees were incubated in a dew chamber for 3 days in darkness at 24°C, then placed in a growth chamber at 22°C with a 12-h photoperiod. Twelve days after inoculation, small lesions were visible on a few of the leaf undersides of each inoculated tree. Not all inoculated leaves developed pustules. No lesions developed on the control trees. M. hiratsukanum has been reported in Canada, Europe, and eastern Asia (3). There are no published reports of this rust in the United States, but there is an unpublished specimen from white alder in the USDA Systematic Mycology Herbarium (BPI 028048) collected from California in 1931, which was identified as M. hiratsukanum by G. B. Cummins using morphological criteria. We are unaware if older specimens of this rust exist because we were unable to search other herbaria in the United States. To the best of our knowledge, this rust has been present in California since 1931, but has only recently been found causing disease in nursery plants. There have been no reports of the serious foliar disease symptoms on trees in California wild lands as have been reported in Europe, presumably due to dry summer and fall seasons in white alder's natural habitat.

Voltage-dependent intrinsic bursting in olfactory bulb Golgi cells

In the mammalian olfactory bulb (OB), local synaptic circuits modulate the evolving pattern of activity in mitral and tufted cells following olfactory sensory stimulation. GABAergic granule cells, the most numerous interneuron subtype in this brain region, have been extensively studied. However, classic studies using Golgi staining methods identified many other, nongranule cell types in the OB whose function remains mysterious. Within just the granule cell layer (GCL), Ramón y Cajal described multiple morphologically distinct subtypes of nongranule interneurons including large spiny Blanes cells which exhibit intrinsic persistent activity. Here, we define the intrinsic electrophysiology of a different nongranule interneuronal cell type in the GCL described by Ramón y Cajal, sparsely spiny Golgi cells in the rat OB. Golgi cells exhibit two distinct firing modes depending on the membrane potential: tonic firing and bursting. Golgi cells also generate rebound bursts following the offset of hyperpolarizing steps. We find that both low-threshold burst responses to depolarizing inputs and rebound bursts are blocked by nickel, an antagonist of T-type voltage-gated Ca2+ current. The state-dependent firing behavior we report in OB Golgi cells suggests that the function of these interneurons may dynamically shift from providing rhythmic potent inhibition of postsynaptic target neurons at sniffing frequencies to tonic, subtractive inhibition based on centrifugal modulatory input.

Histopathological and Immunohistochemical Characterization of Spontaneously Occurring Uterine Deciduomas in Young Adult Rats

Uterine deciduomas were found in two female virgin rats, a 15-week-old Lewis rat and a 7-week-old Sprague-Dawley rat. The firm white nodules were located at the base of unilateral uterine horns and were approximately 6 mm and 4 mm in diameter. Histopathologically, the nodules were composed of three areas, each with a distinct type of proliferating cells: large epithelioid decidual cells with round nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (antimesometrial region); compact spindle-shaped cells with oval nuclei and vacuolar cytoplasm (transitional region); and pleomorphic and spiny cells with round to oval nuclei and compact eosinophilic cytoplasm (mesometrial region). These cells proliferated in sheet-like arrangements and transformed into the other types of cells located in surrounding regions. Immunohistochemically, proliferating cells in all regions were strongly positive for proliferating cell nuclear antigen. The proliferating cells were positive for vimentin, and large decidual cells were positive for common acute lymphoblastic leukemia antigen 10, a marker of uterine interstitial cells. Large decidual cells were positive for α-smooth muscle actin and desmin, suggesting differentiation into muscular cells. Progesterone receptor was expressed in all cell types; however, estrogen receptor α was not expressed in the antimesometrial region. These extremely rare tumor-like nodules represent nonneoplastic lesions referred as decidual reactions of endometrial interstitial cells, and their biological behavior is that of a space-occupying benign tumor in young rats. Our cases might provide information as a historical control in toxicity and pharmacological studies in rats.

Cellular components of the human medial amygdaloid nucleus

The medial nucleus (Me) is a superficial component of the amygdaloid complex. Here we assessed the density and morphology of the neurons and glial cells, the glial fibrillary acidic protein (GFAP) immunoreactivity, and the ultrastructure of the synaptic sites in the human Me. The optical fractionator method was applied. The Me presented an estimated mean neuronal density of 1.53 × 10⁵ neurons/mm³ (greater in the left hemisphere), more glia (72% of all cells) than neurons, and a nonneuronal:neuronal ratio of 2.7. Golgi-impregnated neurons had round or ovoid, fusiform, angular, and polygonal cell bodies (10-30 μm in diameter). The length of the dendrites varied, and pleomorphic spines were found in sparsely spiny or densely spiny cells (1.5-5.2 spines/dendritic μm). The axons in the Me neuropil were fine or coarsely beaded, and fibers showed simple or notably complex collateral terminations. The protoplasmic astrocytes were either isolated or formed small clusters and showed GFAP-immunoreactive cell bodies and multiple branches. Furthermore, we identified both asymmetrical (with various small, clear, round, electron-lucent vesicles and, occasionally, large, dense-core vesicles) and symmetrical (with small, flattened vesicles) axodendritic contacts, also including multisynaptic spines. The astrocytes surround and may compose tripartite or tetrapartite synapses, the latter including the extracellular matrix between the pre- and the postsynaptic elements. Interestingly, the terminal axons exhibited a glomerular-like structure with various asymmetrical contacts. These new morphological data on the cellular population and synaptic complexity of the human Me can contribute to our knowledge of its role in health and pathological conditions.

Differences in the ultrastructure of two selected taxa of phytoplankton in a thermally stratified Lake Holzmaar (Germany)

Abstract This paper presents the results of ultrastructural studies and ecological aspects of some phytoplankton species belonging to the groups of cyanobacteria (Planktothrix rubescens, Synechocystis aquatilis) and green algae (Desmodesmus grahneisii). Specimens were collected during summertime from the mesotrophic and stratified Lake Holzmaar (Western Germany) as planktonic forms from the pelagic zone. The highest cyanobacterium concentration was detected in the metalimnion, where the alkaline pH, low phosphorus and high nitrogen contents were recorded. P. rubescens was characterized by straight filaments up to 1000 μm long and 5.4-8 μm wide and numerous aerotopes in cells. The accompanying algae were identified by ultrastructural analysis and photographic documentation was provided. In the case of D. grahneisii, chloroplast was situated in the parietal part of cell, with one large, oval pyrenoid and, in addition, the granular and spiny cell wall was an important taxonomical criterium for the Desmodesmus genus. This is in contrast with the cyanobacterium S. aquatilis, in which a homogeneous content with visible chromatoplasma was mostly distributed throughout the cell. This algal association was stable in the epilimnion characterized by the presence of high temperature, pH values (>8), nitrate nitrogen and oxygen concentrations

Structural Basis of the Inhibitory Functions of the Efferent Systems of the Parietal Cortex

The relative quantitative distributions of all associative and descending efferent fibers and the ultrastructural organization of terminals of the parietal cortex (fields 5 and 7) in the caudate nucleus (NC) and red nucleus (NR) in cats were studied after local point lesions to the cortex in these fields. The maximal projections of associative fibers were found to be to the fundal fields of the motor cortex and the Clare–Bishop field, with a moderate projection to fields 31 and 19, and occasional degenerating fibers to fields 1, 2, 3a, 3d, 30, and 23. Among descending fibers, the most extensive projections were to the NC, NR, reticular nucleus, and midbrain nuclei, as well as to the pontine nuclei, where immunocytochemical studies revealed mainly GABAergic terminals. Electron microscopic studies led to the suggestion that the influences of the parietal cortex are mediated by axospinous synapses of intermediate short-axon spiny cells of the dorsolateral part of the head of the NC and axodendritic synapses of Golgi II cells in the parvocellular part of the NR. Given the maximal involvement of the fundal fields of the motor cortex and the inhibitory subcortical (NC) and stem nuclei (NR, reticular nuclei of the thalamus), midbrain, and pontine nuclei), we suggest that they serve as the morphological substrate mediating the inhibitory integrative function of the parietal cortex.

Neuronal images of the putamen in the adult human neostriatum: a revised classification supported by a qualitative and quantitative analysis

A qualitative analysis of the morphology of human putamen nerve cells involves a detailed description of the structure and features of neurons and, accordingly, their classification into already defined classes and types. In our sample of 301 neurons, 64.78 % (195) were spiny and 35.22 % (106) aspiny cells. By analyzing cell bodies and dendritic trees, we subdivided spiny cells into two types (I and II) and aspiny cells into three types (III, IV and V). Our sample of neurons, classified according to the previously described scheme, consisted of 80 type I, 115 type II, 16 type III, 42 type IV and 48 type V nerve cells. In the present study, after qualitative analysis of microscopic images of the Golgi impregnated neurons of the putamen, we measured/quantified five morphological properties, i.e., the sizes of the soma and dendritic field, shape of the neuron, straightness of individual dendrites and the branching complexity of the dendritic tree, using eight morphometric parameters. Hence, we identify five types of nerve cells in the human putamen: type I-small spiny neurons; type II-large spiny neurons; type III-large aspiny neurons; type IV-neurons with a large soma and a medium dendritic field; and type V-small aspiny neurons. By performing an adequate statistical analysis on these parameters, we point out that the proposed types differ enough in their morphology to warrant our qualitative classification.

Are FoxP2, Otx1 and FoxO3 candidates for deep homology in weakly electric fish?

Event Abstract Back to Event Are FoxP2, Otx1 and FoxO3 candidates for deep homology in weakly electric fish? Erik Harvey-Girard1*, Anna Catarina Giassi1 and Leonard Maler1 1 University of Ottawa, Cellular and Molecular Medecine, Canada During embryological development the teleost telencephalon undergoes eversion while tetrapod telencephalon goes through evagination. This difference in development has caused major problems to establish any homology between teleost and tetrapod telencephalon. We recently determined the extrinsic and intrinsic neuronal connections of weakly electric fish (Apteronotus leptorhynchus) telencephalon. In particular, we observed that the dorsocentral division of the pallium (DC) contains glutamatergic spiny neurons that receive inputs from the dorsolateral (DL) pallium (homologous to the tetrapod hippocampus) and project to midbrain sensory nuclei (optic tectum, torus semicircularis) involved in visual and electrosensory signal processing. This pattern of connectivity is similar to that of the spiny glutamatergic pyramidal cells within the deep neocortical layers (V/VI). We wondered if there was a deep homology between teleost DC neurons and tetrapod neocortical neurons. To test that hypothesis, we investigated some molecular markers from deep neocortical layers (FoxP2 and Otx1) and hippocampus (FoxO3). First, we have cloned the apteronotid homologs of FoxP2, Otx1 and FoxO3. There was, in the case of all three genes, good similarity between the apteronotid and human amino acid sequences: FoxP2 – 78%, Otx1 – 54%, FoxO3 – 71%. The functional domains of these genes were conserved to a far greater extent – on average: FoxP2 – 89%, Otx1 – 76%, FoxO3 – 82%. This led us to hypothesize that the cellular functions of these genes may also be conserved. We then used in situ hybridization to examine the distribution of the mRNA transcripts of these genes in the apteronotid telencephalon. We found that AptFoxP2 and AptOtx1 transcripts were expressed predominantly in DC, with only a few weakly labeled neurons in DL. In contrast, we found that most neurons in DL strongly expressed AptFoxO3 mRNA, while there was only weak expression in a small number of cells within DC. Together with our previous hodological and anatomical data, these data suggest a deep homology exists between teleost DC and tetrapod neocortical deep layers. Furthermore, in accordance with previous studies in other teleosts, our data suggest that there is also a direct homology between teleost DL and mammal hippocampus. Acknowledgements CIHR Keywords: Apteronotus leptorhynchus, Deep homology, dorsal telencephalon, pallium, FOXO3, FoxP2, Hippocampus, Neocortex, Otx1 Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Evolution Citation: Harvey-Girard E, Giassi A and Maler L (2012). Are FoxP2, Otx1 and FoxO3 candidates for deep homology in weakly electric fish?. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00089 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: 18 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Dr. Erik Harvey-Girard, University of Ottawa, Cellular and Molecular Medecine, Ottawa, Ontario, K1H 8M5, Canada, erikhg@uottawa.ca 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 Erik Harvey-Girard Anna Catarina Giassi Leonard Maler Google Erik Harvey-Girard Anna Catarina Giassi Leonard Maler Google Scholar Erik Harvey-Girard Anna Catarina Giassi Leonard Maler PubMed Erik Harvey-Girard Anna Catarina Giassi Leonard Maler 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.

Getting Drowsy? Alert/Nonalert Transitions and Visual Thalamocortical Network Dynamics

The effects of different EEG brain states on spontaneous firing of cortical populations are not well understood. Such state shifts may occur frequently under natural conditions, and baseline firing patterns can impact neural coding (e.g., signal-to-noise ratios, sparseness of coding). Here, we examine the effects of spontaneous transitions from alert to nonalert awake EEG states in the rabbit visual cortex (5 s before and after the state-shifts). In layer 4, we examined putative spiny neurons and fast-spike GABAergic interneurons; in layer 5, we examined corticotectal neurons. We also examined the behavior of retinotopically aligned dorsal lateral geniculate nucleus (LGNd) neurons, usually recorded simultaneously with the above cortical populations. Despite markedly reduced firing and sharply increased bursting in the LGNd neurons following the transition to the nonalert state, little change occurred in the spiny neurons of layer 4. However, fast-spike neurons of layer 4 showed a paradoxical increase in firing rates as thalamic drive decreased in the nonalert state, even though some of these cells received potent monosynaptic input from the same LGNd neurons whose rates were reduced. The firing rates of corticotectal neurons of layer 5, similarly to spiny cells of layer 4, were not state-dependent, but these cells did become more bursty in the nonalert state, as did the fast-spike cells. These results show that spontaneous firing rates of midlayer spiny populations are remarkably conserved following the shift from alert to nonalert states, despite marked reductions in excitatory thalamic drive and increased activity in local fast-spike inhibitory interneurons.

Hydrodynamic effects of spines: A different spin

Lay AbstractWhen placed in a simple linear gradient of velocity, elongate objects, including many phytoplankton, spend the most time with their longest axis aligned with the flow vectors, but they tumble with a frequency that depends on their ratio of length to width. This tumbling is important because it causes relative motion of phytoplankton cells and nearby fluid, thinning chemical boundary layers and thereby speeding diffusive supply of nutrients to the cells, and it also influences phytoplankton encounter rates with grazers. For both oblate and prolate spheroids, shapes resembling a smoothed discus and football, respectively, tumbling frequency can be predicted accurately from simple theory. Many planktonic organisms, however, have complex shapes produced by spines that extend in varying numbers, at varying angles, and to varying distances from the body or cell. We used numerical models to examine how rigid, spiny phytoplankton cells tumble in a simple linear gradient of velocity. We found that their tumbling was in general well approximated by that of the smallest oblate or prolate spheroid that could contain both the cell and its spines. Investigations that examine the tumbling of cells with flexible spines remain to be done.

Functional connectivity of the main intercalated nucleus of the mouse amygdala

Intercalated cells (ITCs) of the amygdala are clusters of GABAergic cells that surround the basolateral complex of the amygdala (BLA). Growing evidence suggests that ITCs are required for the expression of fear extinction. The main intercalated nucleus (Im) is the largest of the ITC clusters and could also be important for emotional processing. We used whole-cell recordings from Im neurons in acute slices of mouse amygdala. We found that these neurons were medium-sized spiny projection cells. Their passive and active membrane responses were consistent with those previously reported in other ITC clusters. The axon of Im neurons was, in many cases, cut at the slice boundaries, suggesting long-range projections. Axonal branches could be detected in several amygdala nuclei where they made functional synapses. We also functionally studied Im cell inputs. Excitatory postsynaptic currents (eEPSCs) were evoked by the stimulation of the Im, intermediate capsula (IC), external capsula (EC) or BLA, when GABAergic transmission was pharmacologically blocked. An occlusion test indicated that fibres recruited by stimulating Im and IC, or Im and EC were distinct. These eEPSCs had both NMDA and AMPA receptor components. Inhibitory postsynaptic currents (eIPSCs) were evoked after the stimulation of the Im, the EC and the BLA, when glutamatergic transmission was pharmacologically blocked. Furthermore, dopamine reversibly hyperpolarised, and decreased the firing frequency and the input resistance of Im cells via dopamine type 1 receptor. Our data suggest that the Im is functionally connected to other amygdala nuclei and is under neuromodulatory influence. We propose that the Im serves as key neuronal substrate of fear extinction.

Wiring Economy of Neocortical Axon Arbors

Event Abstract Back to Event Wiring Economy of Neocortical Axon Arbors J. M. Budd1*, K. Kovács2, A. S. Ferecskó3, P. Buzás4, U. T. Eysel2 and Z. F. Kisvárday5 1 University of Sussex, School of Informatics, United Kingdom 2 Ruhr-Universität Bochum, Department of Neurophysiology, Germany 3 University of Birmingham, College of Medical & Dental Sciences, School of Clinical & Experimental Medicine, United Kingdom 4 University of Pécs, Institute of Physiology, Medical School, Hungary 5 University of Debrecen, Department of Anatomy, Histology & Embryology, Hungary Discovering the organizational principles of cerebral cortex represents a fundamental challenge in neuroscience. Rámon y Cajal proposed that general laws of conservation concerning cellular material (axon and dendritic ‘wire’) and conduction delay regulate neuronal morphology. Yet despite more than a century of research it is not known how well these laws apply to axon arbors in neocortex. Using a variety of graph optimization algorithms, we investigated Cajal’s proposed economy laws in relation to detailed 3D reconstructions of spiny and basket cell axon arbors obtained from in vivo labelling experiments in adult cat visual cortex. Our analysis of these data suggests that individual neocortical axon arbors are not minimized for axonal length (cellular material) but neither are they optimized for conduction delay. Instead neocortical axon arbors in contacting thousands of spatially distributed postsynaptic targets appear to trade-off saving axonal wire for more rapid communication. In particular, the branched structure of neocortical arbors seems to preserve the relationship between axonal propagation latency and cortical distance and ensures a low degree of temporal dispersion axonal latencies, which may be tighter for inhibitory basket cell than excitatory spiny cell axons. This work has implications for our understanding of neocortical organizing principles, coding, and communication. Acknowledgements Research funded by MTA-TKI (242), DFG (SFB509), and the FACETS (FP6-IST-FETPI) project. Keywords: Molecular and cellular neurobiology, Neuroscience Conference: 13th Conference of the Hungarian Neuroscience Society (MITT), Budapest, Hungary, 20 Jan - 22 Jan, 2011. Presentation Type: Abstract Topic: Molecular and cellular neurobiology Citation: Budd JM, Kovács K, Ferecskó AS, Buzás P, Eysel UT and Kisvárday ZF (2011). Wiring Economy of Neocortical Axon Arbors. Front. Neurosci. Conference Abstract: 13th Conference of the Hungarian Neuroscience Society (MITT). doi: 10.3389/conf.fnins.2011.84.00101 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: 03 Mar 2011; Published Online: 23 Mar 2011. * Correspondence: Dr. J. M Budd, University of Sussex, School of Informatics, Brighton, United Kingdom, kisvarday@anat.med.unideb.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 J. M Budd K. Kovács A. S Ferecskó P. Buzás U. T Eysel Z. F Kisvárday Google J. M Budd K. Kovács A. S Ferecskó P. Buzás U. T Eysel Z. F Kisvárday Google Scholar J. M Budd K. Kovács A. S Ferecskó P. Buzás U. T Eysel Z. F Kisvárday PubMed J. M Budd K. Kovács A. S Ferecskó P. Buzás U. T Eysel Z. F Kisvárday 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.

Dendritic morphology of neurons in medial prefrontal cortex, hippocampus, and nucleus accumbens in adult SH rats

We have studied, in spontaneously hypertensive (SH) rats at different ages (2, 4, and 8 months old), the dendritic morphological changes of the pyramidal neurons of the medial prefrontal cortex (mPFC) and hippocampus and medium spiny neurons of the nucleus accumbens (NAcc) induced by the chronic effect of high-blood pressure. As control animals, we used Wistar-Kioto (WK) rats. Blood pressure was measured every 2 months to confirm the increase in arterial blood pressure. Spontaneous locomotor activity was assessed, and then brains were removed to study the dendritic morphology by the Golgi-Cox stain method followed by Sholl analysis. SH animals at 4 and 8 months of age showed decreased spine density in pyramidal neurons from the mPFC and in medium spiny cells from the NAcc. At 8 months of age as well the pyramidal neurons from the hippocampus exhibited a reduction in the number of dendritic spines. An increase in locomotion in a novel environment at all ages in the SH rats was observed. Our results indicate that high-blood pressure alters the neuronal dendrite morphology of the mPFC, hippocampus, and NAcc. The increased locomotion behavior supports the idea that dopaminergic transmission is altered in the SH rats. This could enhance our understanding of the consequences of chronic high-blood pressure on brain structure, which may implicate cognitive impairment in hypertensive patients.

Axon Topography of Layer IV Spiny Cells to Orientation Map in the Cat Primary Visual Cortex (Area 18)

Our aim was to reveal the relationship between layer IV horizontal connections and the functional architecture of the cat primary visual cortex because these connections play important roles in the first cortical stage of visual signals integration. We investigated bouton distribution of spiny neurons over an orientation preference map using in vivo optical imaging, unit recordings, and single neuron reconstructions. The radial extent of reconstructed axons (14 star pyramidal and 9 spiny stellate cells) was ~1.5 mm. In the vicinity of the parent somata (<400 μm), boutons occupied chiefly iso-orientations, however, more distally, 7 cells projected preferentially to non-iso-orientations. Boutons of each cell were partitioned into 1-15 distinct clusters based on the mean-shift algorithm, of which 57 clusters preferred iso-orientations and 43 clusters preferred cross-orientations, each showing sharp orientation preference "tuning." However, unlike layer III/V pyramidal cells preferring chiefly iso-orientations, layer IV cells were engaged with broad orientations because each bouton cluster from the same cell could show different orientation preference. These results indicate that the circuitry of layer IV spiny cells is organized differently from that of iso-orientation dominant layer III/V cells and probably processes visual signals in a different manner from that of the superficial and deeper layers.

Enhanced dendritic spine number of neurons of the prefrontal cortex, hippocampus, and nucleus accumbens in old rats after chronic donepezil administration.

In Alzheimer's disease brains, morphological changes in the dendrites of pyramidal neurons of the prefrontal cortex (PFC) and hippocampus have been observed. These changes are particularly reflected in the decrement of both the dendritic tree and spine number. Donepezil is a potent and selective acetylcholinesterase inhibitor used in the treatment of Alzheimer's disease. We have studied the effect of oral administration of this drug on the morphology of neuronal cells from the brain of aged rats. We examined dendrites of pyramidal neurons of the PFC, dorsal or ventral hippocampus (VH), and medium spiny neurons of the nucleus accumbens (NAcc). Donepezil (1 mg/kg, vo) was administrated every day for 60 days to rats aged 10 and 18 months. Dendritic morphology was studied by the Golgi-Cox stain procedure followed by Sholl analysis at 12 and 20 months ages, respectively. In all Donepezil-treated rats, a significant increment of the dendritic spines number in pyramidal neurons of the PFC and dorsal hippocampus was observed. However, pyramidal neurons of the VH and medium spiny cells of the NAcc only showed an increase in the number of their spines in 12-month-old rats. Our results suggest that Donepezil prevents the alterations of the neuronal dendrite morphology caused by aging.