bluuebunny/crossref_metadata_2025 huggingface dataset:
GABAergic Presubicular Projections to the Medial Entorhinal Cortex of the Rat
Authors: van Haeften Theo , Wouterlood Floris G. , Jorritsma-Byham Barbara , P. Witter Menno
Published: April 2018

We characterized presubicular neurons giving rise to bilateral projections to the medial entorhinal cortex (MEA) of the rat. Retrograde labeling of presubiculo–entorhinal projections with horseradish peroxidase and subsequent GABA immunocytochemistry revealed that 20–30% of the ipsilaterally projecting neurons are GABAergic. No GABAergic projections to the contralateral MEA were observed. GABAergic projection neurons were observed only in the dorsal part of the presubiculum, which, when taking into account the topography of presubicular projections to MEA, indicates that only the dorsal part of MEA receives GABAergic input. The GABAergic projection neurons constitute ∼30-40% of all GABAergic neurons present in the superficial layers of the dorsal presubiculum. Using double-label fluorescent retrograde tracing, we found that the ipsilateral and contralateral presubiculo–entorhinal projections originate from different populations of neurons. Anterograde labeling of presubiculo–entorhinal projections and electron microscopical analysis of labeled terminals substantiated the presence of a restricted GABAergic presubiculo–entorhinal projection. A small fraction of afferents to only ipsilateral dorsal MEA formed symmetrical synapses with dendritic shafts. No symmetrical synapses on spines were noted. Most afferents to the dorsal part of ipsilateral MEA, as well as all afferents to the remaining ipsilateral and contralateral MEA, formed asymmetrical synapses with both spines and dendritic shafts in an almost equal ratio. Thus, we conclude that the majority of the presubiculo–entorhinal projections exert an excitatory effect on both principal neurons and interneurons. The projections from the dorsal part of the presubiculum comprise a small inhibitory component that originates from GABAergic neurons and targets entorhinal interneurons.
Fragile X Mental Retardation Protein: Nucleocytoplasmic Shuttling and Association with Somatodendritic Ribosomes
Authors: Feng Yue , Gutekunst Claire-Anne , Eberhart Derek E. , Yi Hong , Warren Stephen T. , Hersch Steven M.
Published: April 2018

Fragile X syndrome, a leading cause of inherited mental retardation, is attributable to the unstable expansion of a CGG-repeat within the FMR1 gene that results in the absence of the encoded protein. The fragile X mental retardation protein (FMRP) is a ribosome-associated RNA-binding protein of uncertain function that contains nuclear localization and export signals. We show here detailed cellular localization studies using both biochemical and immunocytochemical approaches. FMRP was highly expressed in neurons but not glia throughout the rat brain, as detected by light microscopy. Although certain structures, such as hippocampus, revealed a strong signal, the regional variation in staining intensity appeared to be related to neuron size and density. In human cell lines and mouse brain, FMRP co-fractionated primarily with polysomes and rough endoplasmic reticulum. Ultrastructural studies in rat brain revealed high levels of FMRP immunoreactivity in neuronal perikarya, where it is concentrated in regions rich in ribosomes, particularly near or between rough endoplasmic reticulum cisternae. Immunogold studies also provided evidence of nucleocytoplasmic shuttling of FMRP, which was localized in neuronal nucleoplasm and within nuclear pores. Moreover, labeling was observed in large- and small-caliber dendrites, in dendritic branch points, at the origins of spine necks, and in spine heads, all known locations of neuronal polysomes. Dendritic localization, which was confirmed by co-fractionation of FMRP with synaptosomal ribosomes, suggests a possible role of FMRP in the translation of proteins involved in dendritic structure or function and relevant for the mental retardation occurring in fragile X syndrome.
Involvement of MAP Kinase in Angiotensin II-Induced Phosphorylation and Intracellular Targeting of Neuronal AT1Receptors
Authors: Yang Hong , Lu Di , Vinson Gavin P. , Raizada Mohan K.
Published: April 2018

MAP kinase stimulation is a key signaling event in the AT1receptor (AT1R)-mediated chronic stimulation of tyrosine hydroxylase and norepinephrine transporter in brain neurons by angiotensin II (Ang II). In this study, we investigated the involvement of MAP kinase in AT1R phosphorylation to further our understanding of these persistent neuromodulatory actions of Ang II. Ang II caused a time-dependent phosphorylation of neuronal AT1R. This phosphorylation was associated with internalization and translocation of AT1R into the nucleus. MAP kinase also stimulated phosphorylation of neuronal AT1R. The conclusion that MAP kinase participates in neuronal AT1R phosphorylation and its targeting into the nucleus is supported further by the following. (1) MAP kinase-mediated phosphorylation of AT1R was blocked by the AT1R antagonist losartan; (2) AT1R co-immunoprecipitated with MAP kinase; (3) MAP kinase-kinase inhibitor PD98059 attenuated Ang II-induced phosphorylation of AT1R; and (4) PD98059 blocked Ang II-induced nuclear translocation of AT1Rs. In summary, these observations demonstrate that Ang II-induced phosphorylation of AT1R is mediated by its activation of MAP kinase. A possible role of AT1R translocation into the nucleus on persistent neuromodulatory actions of Ang II has been discussed.
Rapid Coupling of Calcium Release to Depolarization inLimulus polyphemusVentral Photoreceptors as Revealed by Microphotolysis and Confocal Microscopy
Authors: Ukhanov Kyrill , Payne Richard
Published: April 2018

Microphotolysis and confocal microscopy were used to investigate the timing of calcium release and of the electrical response inLimulus polyphemusventral photoreceptors. The fluorescent dyes Fluo-3 and Calcium Green-5N were used to monitor local Ca2+elevations. Photolysis of caged inositol trisphosphate (InsP3) close to the plasma membrane of the light-sensitive rhabdomeral (R-) lobe resulted in Ca2+elevation within 10–20 msec, 20–45 msec before the physiological response to light normally would be detected. Inward ionic current flow and depolarization followed InsP3-induced calcium release within 2.5 ± 3.3 msec. Voltage-clamping the cells and removal of extracellular Ca2+did not affect the timing of the Ca2+elevation that followed the photolysis of caged InsP3or its relationship to the electrical response. In contrast to the physiological response to light, which only released calcium within the R-lobe, photolysis of InsP3elevated Caiin both lobes, although with much greater effect in the R-lobe, as compared with the bulk of the A-lobe, suggesting the presence of InsP3-sensitive calcium stores in both lobes. Photolysis of caged calcium [o-nitrophenyl EGTA (NPE)] at the edge of the R-lobe activated an inward ionic current within 1.8 ± 0.7 msec. This NPE-induced current reversed at a membrane potential of 10 ± 6 mV in the range typical of that of the light-activated current under physiological conditions. Calcium release, therefore, activates an inward current rapidly enough to contribute to the electrical response to light.
Tension Distribution of Single Motor Units in Multitendoned Muscles: Comparison of a Homologous Digit Muscle in Cats and Monkeys
Authors: Schieber Marc H. , Chua Michael , Petit Julien , Hunt Carlton C.
Published: April 2018

To determine whether single motor units (MUs) in multitendoned muscles distribute tension to multiple tendons or instead focus tension selectively on a single tendon, we examined the distribution of tension generated by single MUs in the cat extensor digitorum lateralis (EDLat), and in its macaque homolog, the extensor digiti quarti et quinti (ED45). General properties of MUs (maximal tetanic tension, axonal conduction velocity, and twitch rise time) were similar in these muscles to those reported for other limb muscles in cats and monkeys. Most cat EDLat MUs were found to exert tension rather selectively on one of the three tendons of the muscle. Fast fatigable MUs were slightly but significantly more selective than fast fatigue-resistant and slow MUs. In contrast, and contrary to expectation, the macaque ED45 contained a lower proportion of MUs that exerted tension selectively on one of the two tendons of the muscle, and a higher proportion of relatively nonselective MUs. These findings suggest that the cat EDLat may consist of three functional subdivisions, each acting preferentially on a different tendon, whereas the macaque ED45 is more likely to function as a single multitendoned muscle.
Activation of Amygdala CholecystokininBReceptors Potentiates the Acoustic Startle Response in the Rat
Authors: Frankland Paul W. , Josselyn Sheena A. , Bradwejn Jacques , Vaccarino Franco J. , Yeomans John S.
Published: April 2018

The acoustic startle reflex is a sensitive index of “anxiety” and “fear.” Potentiation of startle by conditioned and unconditioned fear stimuli appears to be mediated by the amygdala. CholecystokininB(CCKB) agonists increase “anxiety” in laboratory animals and induce “panic” in humans. Here, we investigate the role CCKBreceptor-mediated mechanisms in the amygdala in the potentiation of startle. First, intra-amygdala infusions of the CCKBreceptor agonist pentagastrin (0, 0.01, 0.1, 1, and 10 nm) produced a dose-related potentiation of acoustic startle responses. At the highest dose, startle amplitudes were increased up to 90% above preinfusion baseline levels. Second, similar infusions of pentagastrin had no effect on locomotor activity over the same time course, showing that increases in startle responsivity after infusions of pentagastrin are not attributable to nonspecific changes in motor activity. Third, infusions of similar doses of pentagastrin into the striatum or nucleus accumbens did not potentiate startle responses. Fourth, pretreatment with the CCKBreceptor antagonist L-365,260 (0.1 mg/kg, i.p.) attenuated the potentiation of startle produced by intra-amygdala infusions of pentagastrin. Finally, intra-amygdala infusion of the CCKBreceptor-selective antagonist PD-135158 (10 μg) blocked the potentiation of startle produced by i.c.v. infusions of pentagastrin, suggesting that i.c.v. infusions of pentagastrin potentiate startle responses via activation of amygdala CCKBreceptors. These results show that amygdala CCKBreceptor-mediated mechanisms are involved in the potentiation of acoustic startle responses.
Estradiol Increases the Sensitivity of Hippocampal CA1 Pyramidal Cells to NMDA Receptor-Mediated Synaptic Input: Correlation with Dendritic Spine Density
Authors: Woolley Catherine S. , Weiland Nancy G. , McEwen Bruce S. , Schwartzkroin Philip A.
Published: April 2018

Previous studies have shown that estradiol induces new dendritic spines and synapses on hippocampal CA1 pyramidal cells. We have assessed the consequences of estradiol-induced dendritic spines on CA1 pyramidal cell intrinsic and synaptic electrophysiological properties. Hippocampal slices were prepared from ovariectomized rats treated with either estradiol or oil vehicle. CA1 pyramidal cells were recorded and injected with biocytin to visualize spines. The association of dendritic spine density and electrophysiological parameters for each cell was then tested using linear regression analysis. We found a negative relationship between spine density and input resistance; however, no other intrinsic property measured was significantly associated with dendritic spine density. Glutamate receptor autoradiography demonstrated an estradiol-induced increase in binding to NMDA, but not AMPA, receptors. We then used input/output (I/O) curves (EPSP slope vs stimulus intensity) to determine whether the sensitivity of CA1 pyramidal cells to synaptic input is correlated with dendritic spine density. Consistent with the lack of an estradiol effect on AMPA receptor binding, we observed no relationship between the slope of an I/O curve generated under standard recording conditions, in which the AMPA receptor dominates the EPSP, and spine density. However, recording the pharmacologically isolated NMDA receptor-mediated component of the EPSP revealed a significant correlation between I/O slope and spine density. These results indicate that, in parallel with estradiol-induced increases in spine/synapse density and NMDA receptor binding, estradiol treatment increases sensitivity of CA1 pyramidal cells to NMDA receptor-mediated synaptic input; further, sensitivity to NMDA receptor-mediated synaptic input is well correlated with dendritic spine density.
A Test of the Excitability-Gradient Hypothesis in the Swimmeret System of Crayfish
Authors: Mulloney Brian
Published: April 2018

The motor pattern that drives coordinated movements of swimmerets in different segments during forward swimming characteristically begins with a power-stroke by the most posterior limbs, followed progressively by power-strokes of each of the more anterior limbs. To explain this caudal-to-rostral progression, the hypothesis was proposed that the neurons that drive the most posterior swimmerets are more excitable than their more anterior counterparts, and so reach threshold first.

To test this excitability-gradient hypothesis, I used carbachol to excite expression of the swimmeret motor pattern and used tetrodotoxin (TTX), sucrose solutions, and cutting to block the flow of information between anterior and posterior segments. I showed that the swimmeret activity elicited by carbachol is like that produced when the swimmeret system is spontaneously active and that blocking an intersegmental connective uncoupled swimmeret activity on opposite sides of the block.

When anterior and posterior segments were isolated from each other, the frequencies of the motor patterns expressed by anterior segments were not slower than those expressed by posterior segments exposed to the same concentrations of carbachol. This result was independent of the concentration of carbachol applied and of the number of segmental ganglia that remained connected. When TTX was used to block information flow, the motor patterns produced in segments anterior to the block were significantly faster than those from segments posterior to the block.

These observations contradict the predictions of the excitability-gradient hypothesis and lead to the conclusion that the hypothesis is incorrect.
The Neuroprotective Activity of Group-II Metabotropic Glutamate Receptors Requires New Protein Synthesis and Involves a Glial–Neuronal Signaling
Authors: Bruno Valeria , Sureda Francesc X. , Storto Marianna , Casabona Giacomo , Caruso Alessandra , Knopfel Thomas , Kuhn Rainer , Nicoletti Ferdinando
Published: April 2018

The group-II metabotropic glutamate (mGlu) receptor agonists (2S,1′R,2′R,3′R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV), S-4-carboxy-3-hydroxyphenylglycine (4C3HPG), and (2S,1′S,2′S)-2-(carboxycyclopropyl)glycine (L-CCG-I) protected mouse cortical neurons grown in mixed cultures against excitotoxic degeneration induced by a 10 min pulse with NMDA. Protection was observed not only when agonists were added in combination with NMDA but also when they were transiently applied to cultures 6–20 hr before the NMDA pulse. In both cases, neuroprotection was reduced by the group-II mGlu receptor antagonist (2S,1′S,2′S,3′R)-2-(2′-carboxy-3′-phenylcyclopropyl)glycine (PCCG-IV), as well as by the protein synthesis inhibitor cycloheximide (CHX). Both neurons and astrocytes in mixed cultures were immunostained with an antibody that recognized mGlu2 and mGlu3 receptors in recombinant cells. To determine whether astrocytes played any role in the neuroprotection mediated by group-II mGlu receptors, we exposed pure cultures of cortical astrocytes to DCG-IV, 4C3HPG, or L-CCG-I for 10 min. The astrocyte medium collected 2–20 hr after the exposure to any of these drugs was highly neuroprotective when transferred to mixed cultures treated with NMDA. This protective activity was reduced when CHX was applied to astrocyte cultures immediately after the transient exposure to group-II mGlu receptor agonists. We conclude that neuroprotection mediated by group-II mGlu receptors in cultured cortical cells requires new protein synthesis and involves an interaction between neurons and astrocytes.
Post-Transcriptional Regulation of the GAP-43 Gene by Specific Sequences in the 3′ Untranslated Region of the mRNA
Authors: Tsai Kao-Chung , Cansino Victor V. , Kohn Douglas T. , Neve Rachael L. , Perrone-Bizzozero Nora I.
Published: April 2018

We have shown previously that GAP-43 gene expression during neuronal differentiation is controlled by selective changes in mRNA stability. This process was found to depend on highly conserved sequences in the 3′ untranslated region (3′ UTR) of the mRNA. To map the sequences in the GAP-43 3′ UTR that mediate this post-transcriptional event, we generated specific 3′ UTR deletion mutants and chimeras with the β-globin gene and measured their half-lives in transfected PC12 cells. Our results indicate that there are two distinct instability-conferring elements localized at the 5′ and 3′ ends of the GAP-43 3′ UTR. Of these destabilizing elements, only the one at the 3′ end is required for the stabilization of the mRNA in response to treatment with the phorbol ester TPA. This 3′ UTR element consists of highly conserved uridine-rich sequences and contains specific recognition sites for two neural-specific GAP-43 mRNA-binding proteins. Analysis of the levels of mRNA and protein derived from various 3′ UTR deletion mutants indicated that all mutants were translated effectively and that differences in gene expression in response to TPA were attributable to changes in GAP-43 mRNA stability. In addition, the phorbol ester was found to affect the binding of specific RNA-binding proteins to the 3′ UTR of the GAP-43 mRNA. Given that, like the GAP-43 mRNA, its degradation machinery and the GAP-43 mRNA-binding proteins are expressed primarily in neural cells, we propose that these factors may be involved in the post-transcriptional regulation of GAP-43 gene expression during neuronal differentiation.
Mechanism Involved in Initiation and Propagation of Receptor-Induced Intercellular Calcium Signaling in Cultured Rat Astrocytes
Authors: Venance Laurent , Stella Nephi , Glowinski Jacques , Giaume Christian
Published: April 2018

The mechanisms involved in the initiation and the propagation of intercellular calcium signaling (calcium waves) were studied in cultured rat astrocytes. The analysis of calcium waves, induced either by mechanical stimulation or by focal application of ionomycin, indicated that initiation was dependent on the presence of external calcium. In addition, pharmacological experiments indicate that intercellular propagation required PLC activation, integrity of IP3-sensitive internal calcium stores, and functional gap junctions. An extracellular action of ATP or glutamate and participation of voltage-dependent Ca2+channels were tested by using enzymatic degradation, receptor antagonists, and channel blockers, respectively. Because neither the speed of propagation nor the extent of the calcium waves was affected by these treatments, these alternate mechanisms were excluded from playing a role in intercellular calcium signaling. Biochemical assays and focal applications of several agonists (methoxamine, carbachol, glutamate) of membrane receptors to neurotransmitters and peptides (endothelin 1) demonstrated that their ability to trigger regenerative calcium waves depended on phospholipase C activity and inositol phosphate production. Thus, in rat astrocytes, initiation and propagation of calcium waves involve a sequence of intra- and intercellular steps in which phospholipase C, inositol trisphosphate, internal calcium stores, and gap junction channels play a critical role. The identification of these different events allows us to determine several targets at which the level of long-range signaling in astrocytes may be controlled.
Developmental Adaptation of Rat Nociceptive Withdrawal Reflexes after Neonatal Tendon Transfer
Authors: Holmberg Hans , Schouenborg Jens , Yu Yong-Bei , Weng Han-Rong
Published: April 2018

Nociceptive withdrawal reflexes (NWRs) were studied in adult rats in which the movement patterns produced by single muscles had been altered by neonatal tendon transfer. NWRs evoked by cutaneous noxious mechanical and thermal (CO2-laser) stimulation were recorded using electromyography in a decerebrate spinal preparation. The sensitivity distribution within the receptive fields of the NWRs of the extensor digitorum longus and the peronei muscles exhibited changes corresponding to the altered movement patterns. No detectable change of NWRs was found in normal muscles whose receptive fields overlapped that of the modified muscle. Furthermore, NWRs of muscles that regained an essentially normal function after neonatal tendon transfer did not differ from normal. It is proposed that a developmental experience-dependent mechanism, which takes into account the hindlimb movement pattern caused by contraction of single muscles, underlies the functionally adapted organization of adult NWRs.
Orientation Selectivity and the Arrangement of Horizontal Connections in Tree Shrew Striate Cortex
Authors: Bosking William H. , Zhang Ying , Schofield Brett , Fitzpatrick David
Published: April 2018

Horizontal connections, formed primarily by the axon collaterals of pyramidal neurons in layer 2/3 of visual cortex, extend for millimeters parallel to the cortical surface and form patchy terminations. Previous studies have provided evidence that the patches formed by horizontal connections exhibit modular specificity, preferentially linking columns of neurons with similar response characteristics, such as preferred orientation. The issue of how these connections are distributed with respect to the topographic map of visual space, however, has not been resolved. Here we combine optical imaging of intrinsic signals with small extracellular injections of biocytin to assess quantitatively the specificity of horizontal connections with respect to both the map of orientation preference and the map of visual space in tree shrew V1. Our results indicate that horizontal connections outside a radius of 500 μm from the injection site exhibit not only modular specificity, but also specificity for axis of projection. Labeled axons extend for longer distances, and give off more terminal boutons, along an axis in the map of visual space that corresponds to the preferred orientation of the injection site. Inside of 500 μm, the pattern of connections is much less specific, with boutons found along every axis, contacting sites with a wide range of preferred orientations. The system of long-range horizontal connections can be summarized as preferentially linking neurons with co-oriented, co-axially aligned receptive fields. These observations suggest specific ways that horizontal circuits contribute to the response properties of layer 2/3 neurons and to mechanisms of visual perception.
Alterations in Frequency Coding and Activity Dependence of Excitability in Cultured Neurons ofDrosophilaMemory Mutants
Authors: Zhao Ming-Li , Wu Chun-Fang
Published: April 2018

Mutants of theDrosophila dunce(dnc) andrutabaga(rut) genes, which encode a cAMP-specific phosphodiesterase and a calcium/calmodulin-responsive adenylyl cyclase, respectively, are deficient in short-term memory. Altered synaptic plasticity has been demonstrated at neuromuscular junctions in these mutants, but little is known about how their central neurons are affected. We examined this problem by using the “giant” neuron culture, which offers a unique opportunity to analyze mutational effects on neuronal activity and the underlying ionic currents inDrosophila. On the basis of instantaneous frequency and first latency of spikes evoked by current steps, four categories of firing patterns (tonic, adaptive, delayed, and interrupted) were identified in wild-type neurons, revealing interesting parallels to those commonly observed in vertebrate CNS neurons. The distinct firing patterns were correlated with expression of different ratios of 4-aminopyridine- and tetraethylammonium-sensitive K+currents. Subsets ofdncandrutneurons displayed abnormal spontaneous spikes and altered firing patterns. Altered frequency coding in mutant neurons was demonstrated further by using stimulation protocols involving conditioning with previous activity. Abnormal spike activity and reduced K+current remained in double-mutant neurons, suggesting that the opposite effects on cAMP metabolism bydncandrutdo not counterbalance the mutual functional defects. The aberrant spontaneous activity and altered frequency coding in different stimulus paradigms may present problems in the stability and reliability of neural circuits for information processing during certain behavioral tasks, raising the possibility of modulation in neuronal excitability as a cellular mechanism underlying learning and memory.
Distribution of Brain-Derived Neurotrophic Factor (BDNF) Protein and mRNA in the Normal Adult Rat CNS: Evidence for Anterograde Axonal Transport
Authors: Conner James M. , Lauterborn Julie C. , Yan Qiao , Gall Christine M. , Varon Silvio
Published: April 2018

A sensitive immunohistochemical technique was used, along with highly specific affinity-purified antibodies to brain-derived neurotrophic factor (BDNF), to generate a detailed mapping of BDNF immunoreactivity (BDNF-ir) throughout the adult rat CNS. A parallel analysis of sites of BDNF synthesis was performed within situhybridization techniques using a cRNA probe to the exon encoding mature rat BDNF protein. These combined data revealed (1) groups of cell bodies containing diffuse BDNF-ir throughout the CNS that were strongly correlated with fields of cells containing BDNF mRNA; (2) varying degrees of BDNF-ir outside of cell bodies, in what appeared to be fibers and/or terminals; and (3) many regions containing extremely heavy BDNF-immunoreactive fiber/terminal labeling that lacked BDNF mRNA (e.g., medial habenula, central nucleus of the amygdala, bed nucleus of stria terminalis, lateral septum, and spinal cord). The latter observation suggested that in these regions BDNF was derived from anterograde axonal transport by afferent systems. In the two cases in which this hypothesis was tested by the elimination of select afferents, BDNF immunostaining was completely eliminated. These data, along with the observation that BDNF-ir was rarely found within dendrites or fibersen passage, suggest that BDNF protein produced in adult CNS neurons is polarized primarily along axonal processes and is preferentially stored in terminals within the innervation target.
Prostaglandin D Synthase (β-Trace) in Human Arachnoid and Meningioma Cells: Roles as a Cell Marker or in Cerebrospinal Fluid Absorption, Tumorigenesis, and Calcification Process
Authors: Yamashima Tetsumori , Sakuda Kazushige , Tohma Yasuo , Yamashita Junkoh , Oda Hiroshi , Irikura Daisuke , Eguchi Naomi , Beuckmann Carsten T. , Kanaoka Yoshihide , Urade Yoshihiro , Hayaishi Osamu
Published: April 2018

Glutathione-independent prostaglandin D synthase (PGDS) is an enzyme responsible for biosynthesis of prostaglandin D2in the CNS and is identical to a major cerebrospinal fluid protein, β-trace. Although PGDS has been identified recently in rat leptomeninges, little information is available about human meninges or meningiomas. Here, we report PGDS to be expressed consistently in 10 human arachnoid and arachnoid villi and in 21 meningiomas by immunohistochemistry, Western blot, and reverse transcription (RT)-PCR analyses. In arachnoid, PGDS immunoreactivity was seen in arachnoid barrier cells but was negligible in arachnoid trabecula and pia mater. In contrast, in arachnoid villi, PGDS was seen in core arachnoid cells rather than in the cap cell cluster or arachnoid cell layer. Meningioma cells also showed intense immunoreactivity in the perinuclear region, and it was often concentrated within meningocytic whorls and around calcifying psammoma bodies. Immunoelectron microscopic data, when compared with the ultrastructure, showed that PGDS was localized at rough endoplasmatic reticulum of arachnoid and meningioma cells. Western blot showed a 29 kDa immunoreactive band indicating PGDS, but the extent of expression was variable from case to case, which was compatible with immunohistochemical data. RT-PCR revealed PGDS gene expression in all meningiomas studied, regardless of histological subtypes, and also in human arachnoid villi. Because human arachnoid and meningioma cells exclusively express PGDS, it can be considered their specific cell marker. These results show functional differences in various types of meningeal cells attributable to differences in PGDS expression.
GABAAReceptors Mediate Trophic Effects of GABA on Embryonic Brainstem Monoamine NeuronsIn Vitro
Authors: Liu Jiangping , Morrow A. Leslie , Devaud Leslie , Grayson Dennis R. , Lauder Jean M.
Published: April 2018

The inhibitory neurotransmitter GABA may act as a trophic signal for developing monoamine neurons in embryonic rat brain, because GABA neurons and their receptors appear in brainstem during generation of monoamine neurons. To test this hypothesis, we used dissociated cell cultures from embryonic day 14 rat brainstem, which contains developing serotonin (5-HT), noradrenaline (tyrosine hydroxylase; TH), and GABA neurons. Immunocytochemistry and reverse transcription-PCR (RT-PCR) revealed the presence of multiple α, β, γ, and δ subunits in these cultures. Competitive RT-PCR demonstrated high levels of β3 subunit transcripts. Expression of functional GABAAreceptors was demonstrated using36Cl−flux assays. To investigate GABAergic regulation of neuronal survival and growth, cultures were treated for 1–3 din vitrowith 10 μmGABA and/or GABAAantagonist (bicuculline or the pesticide dieldrin). The effects of treatments were quantified by analysis of immunoreactive 5-HT, TH, and GABA neurons. GABAAreceptor ligands differentially regulated neuronal survival and growth depending on neurotransmitter phenotype. GABA exerted positive effects on monoamine neurons, which were countered by bicuculline (and dieldrin, 5-HT neurons only). By itself, bicuculline produced inhibitory effects on both 5-HT and TH neurons, whereas dieldrin potently inhibited 5-HT neurons only. GABA neurons responded positively to both antagonists, but more strongly to bicuculline. Taken together, these results demonstrate that the activation/inhibition of GABAAreceptors produces opposite effects on the development of embryonic monoamine and GABA neurons. This suggests that these neurotransmitter phenotypes may express GABAAreceptors that differ in fundamental ways, and these differences determine the developmental responses of these cells to GABAergic stimuli.
Directed Growth of Early Cortical Axons Is Influenced by a Chemoattractant Released from an Intermediate Target
Authors: Richards Linda J. , Koester Susan E. , Tuttle Rebecca , O’Leary Dennis D. M.
Published: April 2018

Projection neurons throughout the mature mammalian neocortex extend efferent axons either through the ventrolaterally positioned internal capsule to subcortical targets or through the dorsally located midline corpus callosum to the contralateral cortex. In rats, the internal capsule is pioneered on E14, but the corpus callosum is not pioneered until E17, even though these two types of projection neurons are generated at the same time. Here we use axonal markers to demonstrate that early cortical axon growth is directed toward the nascent internal capsule, which could account for the timing difference in the development of the two efferent pathways. This directed axon growth may be due to a chemoattractant and/or a chemorepellent secreted by intermediate targets of cortical efferent axons, the nascent internal capsule, or the medial wall of the dorsal telencephalon (MDT), respectively. To test for these soluble activities, explants of E15 rat neocortex and intermediate targets were cocultured in collagen gels. Cortical axon outgrowth was directed toward the internal capsule, but outgrowth was nondirected and suppressed when cocultured with MDT, suggesting that the internal capsule releases a chemoattractant for cortical axons, whereas the MDT releases a chemosuppressant. Because the chemoattractant Netrin-1 is expressed in the internal capsule, we cocultured cortical explants with E13 rat floor plate, which expresses Netrin-1, or with Netrin-1-transfected or control-transfected 293T cells. Cortical axon growth was directed toward both floor plate and Netrin-1-transfected 293T cells, as it had been toward the internal capsule, but not toward control-transfected 293T cells. These findings suggest that early events in cortical axon pathfinding may be controlled by a soluble activity which attracts initial axon growth toward the internal capsule and that this activity may be due to Netrin-1.
The Effects of Nerve Growth Factor on Spatial Recent Memory in Aged Rats Persist after Discontinuation of Treatment
Authors: Frick Karyn M. , Price Donald L. , Koliatsos Vassilis E. , Markowska Alicja L.
Published: April 2018

Nerve growth factor (NGF) infusion significantly reduces spatial recent memory deficits in aged rats, an effect that has great relevance to the treatment of memory impairments characteristic of patients with Alzheimer’s disease. The present study was designed to examine whether this NGF-induced improvement in spatial recent memory persists after the discontinuation of NGF treatment, an issue of crucial importance for the potential clinical use of this compound. Spatial recent memory was tested in a Morris water maze delayed nonmatch-to-position task. In addition to memory, sensorimotor skills were also examined. Four- and 22-month-old rats were tested preoperatively, infused intraventricularly with recombinant human NGF or vehicle, and tested both during the 4 week infusion period and during the 4 weeks after discontinuation of the infusion. NGF significantly improved spatial recent memory in 22-month-old rats only, during the 4th week of infusion and for up to 4 weeks after discontinuation of the infusion. Although NGF did not affect overall sensorimotor skills during infusion in either age group, sensorimotor skills were significantly improved both 2 and 4 weeks after discontinuation of infusion in 22-month-old rats. These findings demonstrate that the beneficial effects of NGF on spatial recent memory can persist for up to 1 month after discontinuation of infusion and suggest that NGF can be used intermittently for the treatment of age-associated memory dysfunction and Alzheimer’s disease.
Temporal Integration and Duration Tuning in the Dorsal Zone of Cat Auditory Cortex
Authors: He Jufang , Hashikawa Tsutomu , Ojima Hisayuki , Kinouchi Yohsuke
Published: April 2018

The present study examined auditory cortical neurons, the responses of which depended on the duration of noise bursts. We recorded from 150 neurons with response latencies exceeding 30 msec and from 28 neurons with OFF responses to auditory stimuli in the dorsal zone of cat auditory cortex. Of 150 long-latency neurons, 132 displayed some form of duration selectivity. Seventy-eight were classified as selective for long durations. Among the long-duration-selective neurons, 30 responded only to noise burst stimuli with durations longer than a minimal threshold and were classified further as duration threshold neurons. Of 132 duration-selective neurons, 41 responded selectively to noise bursts of short duration; 13 showed maximal responses to noise bursts of a particular duration and could be regarded as duration-tuned neurons. OFF-response neurons included ones that were long-duration-selective, duration-tuned, and nonduration-selective.

Duration tuning has been described previously only at the midbrain level in amphibians and bats. The present finding of sensitivity to sound duration in at least one region of cat auditory cortex indicates that this form of neural tuning may be important for hearing in all vertebrates, and for processing of sound at multiple levels in the auditory pathway. The duration tuning in the cat auditory cortex was much broader, and the best duration was distributed over a wider range than in the bat inferior colliculus. We suggest that the duration selectivity of the long-latency neurons results from integration along the time domain of a stimulus during the latent period.
Nitric Oxide Facilitates Long-Term Potentiation, But Not Long-Term Depression
Authors: Malen Peter L. , Chapman Paul F.
Published: April 2018

Reports that nitric oxide synthase (NOS) inhibition prevents the induction of long-term potentiation (LTP) have been controversial. Recent evidence suggests that NO may help to regulate the threshold for LTP induction. We have tested this hypothesis by examining the effects of stimulus frequency and train duration on synaptic plasticity in the presence of either NO donors or NOS inhibitors. Two different NO donors facilitated LTP induction by stimuli that normally produced only short-term potentiation, whereas NOS inhibitors blocked LTP to stimuli that normally produce small LTP. NO donors facilitated LTP induction even when NMDA receptors were blocked, indicating that NO need not act via NMDA receptors. NO donors and NOS inhibitors were without effect on long-term depression (LTD), suggesting that they act on a distinct potentiating mechanism. Thus, NO could contribute to the establishment of plasticity under physiologically relevant conditions by selectively increasing the probability of LTP induction.
K+Channel Expression and Cell Proliferation Are Regulated by Intracellular Sodium and Membrane Depolarization in Oligodendrocyte Progenitor Cells
Authors: Knutson Peter , Ghiani Cristina A. , Zhou Jia-Min , Gallo Vittorio , McBain Chris J.
Published: April 2018

The effects of a variety of antiproliferative agents on voltage-dependent K+channel function in cortical oligodendrocyte progenitor (O-2A) cells were studied. Previously, we had shown that glutamate receptor activation reversibly inhibited O-2A cell proliferation stimulated by mitogenic factors and prevented lineage progression by attenuating outward K+currents in O-2A cells. We now show that the antiproliferative actions of glutamate receptor activation are Ca2+-independent and arise from an increase in intracellular Na+and subsequent block of outward K+currents. In support of this mechanism, agents that acted to depolarize O-2A cells or increase intracellular sodium similarly had an antiproliferative effect, attributable at least in part to a reduction in voltage-gated K+currents. Also, these effects were reversible and Ca2+-independent. Chronic treatment with glutamate agonists was without any long-term effect on K+current function. Cells cultured in elevated K+, however, demonstrated an upregulation of inward rectifier K+currents, concomitant with an hyperpolarization of the resting membrane potential. This culture condition therefore promoted a current phenotype typical of pro-oligodendroblasts. Finally, cells chronically treated with the mitotic inhibitor retinoic acid displayed a selective downregulation of outward K+currents. In conclusion, signals that affect O-2A cell proliferation do so by regulating K+channel function. These data indicate that the regulation of K+currents in cells of the oligodendrocyte lineage plays an important role in determining their proliferative potential and demonstrate that O-2A cell K+current phenotype can be modified by long-term depolarization of the cell membrane.
Molecular Cloning and Characterization of anl-Epinephrine Transporter from Sympathetic Ganglia of the Bullfrog,Rana catesbiana
Authors: Apparsundaram Subramaniam , Moore Kimberly R. , Malone M. D. , Hartzell H. Criss , Blakely Randy D.
Published: April 2018

Chemical signaling by dopamine (DA) andl-norepinephrine (l-NE) at synapses is terminated by uptake via specialized presynaptic transport proteins encoded by the DA transporter (DAT) andl-NE transporter (NET) genes, respectively. In some vertebrate neurons, particularly the sympathetic neurons of amphibians,l-NE is converted tol-epinephrine (l-Epi, adrenaline) and released as the primary neurotransmitter. Although evidence exists for a molecularly distinctl-Epi transporter (ET) in the vertebrate brain and peripheral nervous system, a transporter specialized for extracellularl-Epi clearance has yet to be identified. To pursue this issue, we cloned transporter cDNAs from bullfrog (Rana catesbiana) paravertebral sympathetic ganglia and characterized functional properties via heterologous expression in non-neuronal cells. A cDNA of 2514 bp (fET) was identified for which the cognate 3.1 kb mRNA is highly enriched in frog sympathetic ganglia. Sequence analysis of the fET cDNA reveals an open reading frame coding for a protein of 630 amino acids. Inferred fET protein sequence bears 75, 66, and 48% amino acid identity with human NET, DAT, and the 5-hydroxytryptamine transporter (SERT), respectively. Transfection of fET confers Na+- and Cl−-dependent catecholamine uptake in HeLa cells. Uptake of [3H]-l-NE by fET is inhibited by catecholamines in a stereospecific manner.l-Epi and DA inhibit fET-mediated [3H]-l-NE uptake more potently than they inhibit [3H]-l-NE uptake by human NET (hNET), whereasl-NE exhibits equivalent potency between the two carriers. Moreover, fET exhibits a greater maximal velocity (Vmax) for the terminal products of catecholamine biosynthesis (l-Epi >l-NE ≫ DA), unlike hNET, in which aVmaxrank order ofl-NE > DA >l-Epi is observed. fET-mediated transport of catecholamines is sensitive to cocaine and tricyclic antidepressants, with antagonist potencies significantly correlated with hNET inhibitor sensitivity. Amino acid conservation and divergence of fET with mammalian catecholamine transporters help define residues likely to be involved in catecholamine recognition and translocation as well as blockade by selective reuptake inhibitors.
An Antibody to the Tetraspan Membrane Protein CD9 Promotes Neurite Formation in a Partially α3β1 Integrin-Dependent Manner
Authors: Banerjee Shilpi A. , Hadjiargyrou Michael , Patterson Paul H.
Published: April 2018

The tetraspan cell surface glycoprotein, CD9, has been implicated in cellular signaling during growth and differentiation in the hematopoietic and nervous systems. Because CD9 expression is induced early in development in sensory and sympathetic neuroblasts, we investigated the role of CD9 in neurite outgrowth. We plated dissociated cells from neonatal sympathetic ganglia on immobilized anti-CD9 antibodies or antibodies against other cell surface molecules. We show here that B2C11, an anti-CD9 antibody that has been shown previously to activate Schwann cellsin vitro, promotes robust neurite outgrowth from sympathetic neurons that is greater than that on other antibody surfaces and is comparable to neurite outgrowth on a collagen substratum. In addition, B2C11 causes dramatic morphological changes in neurons and glia from dissociated ganglia, including a flattening of these cells.

Because CD9 interacts with integrins in many cell types including Schwann cells, and specifically with the α3β1 integrin in some cells, we tested whether the effect of B2C11 on neurite outgrowth is mediated by this integrin. An anti-α3β1 antibody, Ralph 3–1, attenuates the extent of neurite outgrowth on B2C11 and collagen, but not on laminin. Because the α3β1 integrin has been shown to mediate neurite outgrowth on different substrates, these results provide a functional significance for the CD9-α3β1 interaction; downstream signaling may be activated by thiscisinteraction on the cell surface in response to external cues that promote neurite outgrowth.
Presynaptic Control of Subunit Composition of NMDA Receptors Mediating Synaptic Plasticity
Authors: Gottmann Kurt , Mehrle Alexander , Gisselmann Günter , Hatt Hanns
Published: April 2018

Subunit composition of subsynaptic transmitter receptors is controlled presynaptically in the developing neuromuscular junction. To investigate presynaptic regulation of NMDA receptor subunit composition in the CNS, we co-cultured different types of hippocampal explants with dissociated target neurons. Postsynaptic NMDA receptors were studied using whole-cell patch-clamp recordings.

After 1 week in culture with innervation by dentate gyrus (dg) explants, the kinetic and pharmacological properties of postsynaptic NMDA receptors indicated the expression of NMDA receptor subtypes containing NR2B subunits (NR1/NR2A/NR2B or NR1/NR2B or both). The properties of NMDA receptors in noninnervated neurons were similar to those of neurons innervated by dg explants. In contrast, after innervation by explants from the cornu ammonis (CA) region, we found an additional NMDA receptor subtype with properties consistent with the subunit composition NR1/NR2A. These findings indicate that presynaptic signals determine NMDA receptor subunit composition.

After prolonged cultivation (11–12 d) the properties of synaptic NMDA receptors in the majority of dg-innervated neurons also indicated the expression of NR1/NR2A receptors. This suggests a delayed developmental maturation of NMDA receptors in dg-innervated neurons.

Long-term plasticity of central glutamatergic synapses is critically influenced by the subunit composition of NMDA receptors, and thus presynaptic control of NMDA receptor subunit composition might regulate synaptic plasticity.
The Generation of Neuronal Heterogeneity in a Rat Sensory Ganglion
Authors: Hall Alison K. , Ai Xingbin , Hickman Georgia E. , MacPhedran Sally E. , Nduaguba Constance O. , Robertson Christie P.
Published: April 2018

Adult sensory neurons differ chemically, morphologically, and functionally, but the factors that generate their diversity remain unclear. For example, neuropeptides are generally found in small neurons, whereas abundant neurofilament is common in large neurons. Neurons containing the neuropeptides calcitonin gene-related peptide (CGRP) or substance P were quantified using immunohistochemistry in rat lumbar dorsal root ganglion (DRG) at times before and after sensory neurons contact central and peripheral targetsin vivo. No neurons in the newly formed DRG expressed neuropeptide or neuropeptide mRNA, but neuropeptides were detectable about the time that axons connect with peripheral targets. To determine the requirement for target in neuropeptide regulation, embryonic DRG neurons were isolated at times before central and peripheral connections had formed, placed in culture, and immunocytochemically assayed for CGRP and substance P. Cultured neurons expressed neuropeptides with a time course and in proportions similar to thosein vivo. Thus, some neurons in the embryonic DRG seem to be intrinsically specified to later express CGRP and substance P. The percentage of CGRP-immunoreactive neurons was not changed by cell density, non-neuronal cells, neurotrophins in addition to nerve growth factor (NGF), or antibody inactivation of neurotrophin-3 in the presence of NGF. To test the role of extrinsic cues on CGRP expression, DRG neurons were co-cultured with potential target tissues. Co-culture with a rat epidermal or smooth muscle cell line increased the proportion of CGRP-containing neurons, whereas primary skeletal muscle and 3T3 cells had no effects. Thus, multiple appropriate sensory neuron phenotypes arise in a regulated fashion in cultured neurons isolated before target connections have formed, and some candidate target tissues can modulate that intrinsic expression pattern.