bluuebunny/crossref_metadata_2025 huggingface dataset:
Perturbation of intracellular calcium and hydrogen ion regulation in cultured mouse hippocampal neurons by reduction of the sodium ion concentration gradient
Authors: Koch RA , Barish ME
Published: April 2018

Na(+)-Ca2+ exchange has been identified as a mechanism for regulation of intracellular Ca ion concentration ([Ca2+]i) in neurons of invertebrates and vertebrates, but for mammalian central neurons its role in restoration of resting [Ca2+]i after transient increases induced by stimulation has been less clear. We have examined the recovery of [Ca2+]i following K+ depolarization and glutamate receptor activation of cultured mouse hippocampal neurons using the Ca(2+)- sensitive dye Fura-2. Reduction of the transmembrane Na+ gradient by removal of external Na+ slowed the recovery of neurons from imposed Ca2+ loads. We observed that [Ca2+]i regulation was disrupted more severely when N-methyl-D-glucamine (N-MG), Tris, or choline rather than Li+ replaced external Na+. Additional disruption of intracellular pH regulation by substitutes other than Li+ may account for this difference. Measurement of [Ca2+]i and [H+]i (using the H(+)-sensitive dye BCECF) during glutamate receptor activation indicated that Ca2+ influx resulted in production of intracellular H+, and that Li+ but not N-MG could prevent cytoplasmic acidification on removal of external Na+. We also observed that intracellular acidification alone was sufficient to slow recovery from Ca2+ load. We conclude, therefore, that Na(+)-Ca2+ exchange contributes to recovery of [Ca2+]i after stimulation leading to Ca2+ entry into hippocampal neurons, and that Na(+)-H+ exchange limits the acidification (and secondary increase in [Ca2+]i) that accompanies Ca2+ influx. We suggest that because both Na(+)-Ca2+ and Na(+)-H+ exchangers will be compromised during ischemia and hypoglycemia, increased intracellular H+ may synergize with cytoplasmic Ca2+ to potentiate excitotoxic neuronal death.
Synaptic and nonsynaptic localization of the GluR1 subunit of the AMPA- type excitatory amino acid receptor in the rat cerebellum
Authors: Baude A , Molnar E , Latawiec D , McIlhinney RA , Somogyi P
Published: April 2018

The cellular and subcellular distribution of the GluR1 subunit of the AMPA-type excitatory amino acid receptor was determined in the cerebellar cortex of rat using immunocytochemistry. Two polyclonal antibodies were raised against the N- and C-terminal regions of the subunit. They both labeled a band in immunoblots of rat cerebellar membranes with a molecular weight corresponding to that predicted for this subunit of 105 kDa molecular mass. In light microscopy the distribution of immunoreactivity for the two antibodies was very similar. The molecular layer was strongly immunoreactive whereas no labeling was observed in the granular layer. Electron microscopy revealed that the antibody raised against the N-terminal part of the subunit recognizes an extracellular epitope(s), whereas the antibody against the C-terminal part recognizes an intracellular epitope(s) along the plasma membrane. In Bergmann glial cells the endoplasmic reticulum, Golgi apparatus, and multivesicular bodies were labeled, presumably demonstrating sites of synthesis and degradation for the GluR1 subunit, respectively. Immunoreactivity was associated with Bergmann glial processes surrounding Purkinje cell dendrites, spines, and the glutamate-releasing axon terminals of the parallel and climbing fibers. This suggests that the neurotransmitter glutamate and the AMPA- type glutamate receptors are involved in neuronal/glial communication. The GluR1 subunit was also found at glial membranes in contact with other glial cells. Purkinje cells showed immunoreactivity in the endoplasmic reticulum and multivesicular bodies. No immunoreaction was detected in basket and stellate cells. Immunoreactivity was observed at type 1 synaptic junctions, including the synaptic cleft. These synaptic junctions were between spines, often originating from Purkinje cell dendrites, and parallel or climbing fiber terminals. Our results demonstrate that the GluR1 subunit of the AMPA-type ionotropic excitatory amino acid receptor is present at both parallel and climbing fiber synapses, which are surrounded by glial processes containing the same receptor subunit.
Glutamate uptake inhibition by oxygen free radicals in rat cortical astrocytes
Authors: Volterra A , Trotti D , Tromba C , Floridi S , Racagni G
Published: April 2018

Formation of reactive oxygen species and disfunction of the excitatory amino acid (EAA) system are thought to be key events in the development of neuronal injury in several acute and long-term neurodegenerative diseases. Recent evidence suggests that the two phenomena may be interdependent. The present study is aimed at exploring possible molecular mechanisms underlying oxygen radical-EAA interaction. Exposure of cortical astrocytic cultures to either xanthine + xanthine oxidase (X/XO), a free radical-generating system, or hydrogen peroxide (H2O2) results in a marked decrease of high-affinity glutamate transport. Within 10 min of X/XO application, uptake falls to approximately 60% of its control value. In parallel no detectable release of lactate dehydrogenase occurs. X/XO effect is abolished in the presence of a mixture of scavenger enzymes (superoxide dismutase+catalase) or by the disulfide-reducing agents glutathione and dithiothreitol (DTT), but not by lipophilic antioxidants or ascorbate. The time course of inhibition shows an almost linear decline of glutamate transport during cell exposure to free radicals, while upon their inactivation the decline stops but established inhibition persists for at least 1 hr. In this situation, application of DTT significantly restores transport function. These data suggest that free radicals inhibit glutamate uptake primarily by long-lasting oxidation of protein sulfhydryl (SH) groups. Chemical modifiers of free SH groups, such as p-chloromercuribenzoate and N-ethylmaleimide, also induce uptake inhibition. Na+/K+ ATPase is a known target of oxygen radicals and may be involved in glutamate uptake inhibition. Indeed, ouabain, a blocker of the pump, reduces uptake in astrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
The NH2-terminus of substance P modulates NMDA-induced activity in the mouse spinal cord
Authors: Hornfeldt CS , Sun X , Larson AA
Published: April 2018

Excitatory amino acids (EAAs) and substance P are believed to transmit nociceptive information in the spinal cord. As substance P NH2-terminal fragments can modulate non-NMDA EAA-mediated activity, we examined the effects of substance P fragments to ascertain whether the COOH- or NH2- terminus of substance P modulates the actions of NMDA in the spinal cord. NMDA activity was measured by the intensity of behaviors produced by NMDA (0.2 nmol) administered intrathecally in the mouse. The NMDA response was attenuated after pretreatment with either substance P (22.5 pmol, 30 min) or the NH2-terminal fragment of substance P, SP-(1– 7). Pretreatment with the COOH-terminal fragment SP-(5–11) (22.5 pmol, 30 min), a neurokinin ligand, had no effect on NMDA-induced behaviors, suggesting that the inhibitory effect of substance P is caused by the NH2-terminus. Pretreatment with D-Pro2,D-Phe7 substance P-(1–7), a SP- (1–7) antagonist, potentiated NMDA activity, suggesting a tonic inhibitory effect of the substance P NH2-terminus. Desensitization to NMDA typically develops when NMDA is injected at 2 min intervals. While pretreatment with SP-(1–7) inhibited NMDA, coadministration of SP-(1–7) (22.5 pmol), with the first of four injections of NMDA, first inhibited but then potentiated responses to each challenge with NMDA. Coadministration of the same dose of SP-(1–7) with the fourth injection of NMDA immediately potentiated the response to NMDA.(ABSTRACT TRUNCATED AT 250 WORDS)
Structural plasticity in the Drosophila brain
Authors: Heisenberg M , Heusipp M , Wanke C
Published: April 2018

The Drosophila brain is highly variable in size. Female flies grown in densely populated larval cultures have up to 20% more Kenyon cell fibers in their mushroom bodies than flies from low-density cultures. These differences in the number of Kenyon cell fibers are accompanied by differences in the volume of the calyx. During imaginal life, volume changes are observed in the calyces, all parts of the optic lobes, the central brain, and central complex. They occur not only in the first week of adulthood but also between days 8 and 16. Factors causing these changes are little understood. In flies kept in pairs for 1 week, the size of the calyx but not of the lobula is influenced by the sex of the partner. Females have larger calyces if the partner is female than if it is male. Males seem to be affected in the same way. Females living solitarily in little food vials for the first week of their imaginal life have smaller lobulae than females having spent the week in a populated flight cage. Males and females of heterosexual groups of 40 animals have still smaller lobulae, medullae, and calyces than their siblings kept in isolation. In addition, brain size is influenced by yet unidentified factors causing long and short trends. The data suggest that in Drosophila, most neuropil regions of the brain are continuously reorganized throughout life in response to specific living conditions.
Spatial memory deficits, increased phosphorylation of the transcription factor CREB, and induction of the AP-1 complex following experimental brain injury
Authors: Dash PK , Moore AN , Dixon CE
Published: April 2018

Traumatic brain injury causes both short- and long-term neurological impairments. A cascade of biochemical changes triggered by the injury may increase the expression of several genes, which has been hypothesized to contribute to the observed cognitive deficits. The mechanism(s) of induction for these genes is not yet known. We present evidence that lateral cortical impact injury in rats that produces spatial memory deficits also increases phosphorylation of the transcription factor CREB (cAMP response element binding). Subsequent to the phosphorylation of CREB, c-Fos expression and the AP-1 complex are enhanced. The temporal and spatial activation of c-Fos is consistent with it being induced by phosphorylated CREB proteins. Thus, CREB-mediated gene activation may contribute to the observed behavioral deficits. Further elucidation of the biochemical and pathophysiological changes will be of importance for clinical therapy.
Cholinergic manipulations in the medial septal area: age-related effects on working memory and hippocampal electrophysiology
Authors: Markowska AL , Olton DS , Givens B
Published: April 2018

Aged rats have impairments in several types of cognitive functions, including spatial working memory (WM), that are dependent upon the septohippocampal cholinergic system. The present series of experiments was designed to assess the effectiveness of pharmacological manipulations of the medial septal area (MSA) in order to influence the physiology of the septohippocampal pathway and, therefore, the brain functions in which this pathway participates. Aged (22MO) and young (4MO) Fischer-344 rats received microinfusions into the MSA with either saline, the muscarinic agonist, oxotremorine (OXO), or the muscarinic antagonist, scopolamine (SCOP). Working memory was tested in a T-maze spatial alternation task, prior to infusion, immediately after infusion, and 90 min after infusion. Hippocampal theta activity and the population excitatory postsynaptic potential (pEPSP) of the dentate gyrus to perforant path stimulation were recorded immediately following behavioral testing at each of the three time periods. In 22MO rats, intraseptal OXO (0.5 micrograms, 2 micrograms, 5 micrograms) produced a dose-dependent improvement in choice accuracy, a shift of the hippocampal theta peak to a lower frequency and a higher peak power, and an increase in the initial slope of pEPSP. OXO, 0.1 microgram, did not have an effect on behavior or hippocampal physiology and OXO, 10 micrograms, produced an impairment in performance. In 4MO rats, OXO did not affect choice accuracy, nor the pEPSP slope, but altered hippocampal theta peak frequency and power similarly as in 22MO. The lowest behaviorally effective dose, 0.5 microgram OXO, did not influence WM performance when infused into the lateral ventricles (intracerebroventricularly) of either 22MO or 4MO rats. SCOP (2 micrograms, 5 micrograms, 15 micrograms) decreased choice accuracy in a dose-dependent fashion in both 22MO and 4MO rats. However, in 22MO rats, the behavioral dose-response curve for scopolamine was shifted towards greater sensitivity. SCOP produced a shift of the hippocampal theta to a higher frequency and a lower peak power, and a decrease in the initial slope of pEPSP. In 4MO rats, SCOP altered hippocampal theta similarly to 22MO, but did not affect the pEPSP slope. These results indicate that (1) cholinergic receptors in the MSA are a useful target for drugs to improve WM in aging rats, (2) age-related changes in the activity of the septohippocampal pathway may increase its sensitivity to drugs which alter its activity, and (3) alterations in hippocampal physiology may contribute differently to changes in WM in young and in old rats.
Phosphorylation of rabphilin-3A by Ca2+/calmodulin- and cAMP-dependent protein kinases in vitro
Authors: Fykse EM , Li C , Sudhof TC
Published: April 2018

Regulation of neurotransmitter release is thought to involve modulation of the release probability by protein phosphorylation. In order to identify novel targets for such regulatory processes, we have studied the phosphorylation of rabphilin-3A in vitro. Rabphilin-3A is a synaptic vesicle protein that interacts with rab3A in a GTP-dependent manner and binds Ca2+ in a phospholipid-dependent manner. Here we show that rabphilin-3A is an efficient substrate for Ca2+/calmodulin- dependent protein kinase II, which phosphorylates rat rabphilin-3A at residue 234 and 274, and for cAMP-dependent protein kinase, which phosphorylates rat rabphilin-3A at residue 234. This identifies the middle region of rabphilin-3A situated between the N-terminal rab3A- binding sequences and the C-terminal C2-domains involved in Ca2+/phospholipid binding as a regulatory domain. Thus, rabphilin-3A is a second phosphoprotein on synaptic vesicles that, similar to synapsin I, may integrate phosphorylation signals from multiple protein kinase signaling pathways in the cell.
Induction of L1 mRNA in PC12 cells by NGF is modulated by cell-cell contact and does not require the high-affinity NGF receptor
Authors: Itoh K , Brackenbury R , Akeson RA
Published: April 2018

We examined the effects of nerve growth factor (NGF) and cell-cell contact on expression of the neural cell adhesion molecule L1 in PC12 cells. After 7 d exposure to NGF, but not after exposure to EGF, FGF, TGF beta, or dibutyryl cAMP (dbcAMP), L1 mRNA levels increased fourfold. This increase was not blocked by K252a, an inhibitor of the high-affinity NGF receptor, although neurite extension was completely inhibited. L1 mRNA levels also increased in NGF-treated mutant PC12 cells (PC12nnr5) that lack the high-affinity NGF receptor. The effect of NGF on L1 mRNA was greatest in cells cultured at high density, but its effect on cells cultured at low density was augmented by antibody to L1 (to mimic L1 homophilic binding). Various extracellular matrix components had no differential effects on L1 mRNA levels in either the presence or absence of NGF. Together, these findings suggest that NGF regulates L1 expression by a mechanism that is independent of the high- affinity NGF receptor and that this regulation is modulated by cell- cell contact but not by cell-extracellular matrix interactions.
Complementary expressions of transcripts encoding GAD67 and GABAA receptor alpha 4, beta 1, and gamma 1 subunits in the proliferative zone of the embryonic rat central nervous system
Authors: Ma W , Barker JL
Published: April 2018

The developmental stage at which nerve cells initially express specific neurotransmitters and their corresponding receptors remains elusive. In the present study, the distribution patterns of transcripts for the GABA-synthesizing enzyme, glutamate decarboxylase (GAD67), and specific GABAA receptor subunits were examined in the proliferative zone of the rat central nervous system using in situ hybridization. In order to define the DNA synthetic zone of the germinal matrix, tissue sections were taken from embryos whose mothers had been injected with 5-bromo-2′- deoxyuridine (BrdU) and had survived for 1 hr. BrdU immunocytochemistry was used to locate the relative position of BrdU-immunoreactive nuclei within the ventricular zone (VZ). At embryonic day (E) 15 in the alar plate of the lumbar spinal cord, and at E17 and E20 in the dorsomedial sector of the neocortex, densely packed BrdU-immunoreactive nuclei were consistently detected in lateral portions of the inner half of the germinal matrix, indicating that the inner half of the germinal matrix corresponded to the VZ, while the outer half corresponded to the transitional (TZ) or subventricular zone (SV). In situ hybridization in tissue sections adjacent to BrdU-immunoreacted ones showed that the transcripts for GABAA receptor alpha 3, beta 3, and gamma 2 subunits were found exclusively in the mantle zone, while those for alpha 4, beta 1, and gamma 1 subunits were predominantly detected in the inner half of the germinal matrix (i.e., VZ). Furthermore, in the E15 germinal matrix of the lumbar spinal cord, cells exhibiting alpha 4 subunit mRNA were much more abundant in the receding intermediate plate, which contains mostly postmitotic cells, than in the alar plate comprised of many DNA-synthesizing cells, strongly suggesting that only those cells completing final cell division expressed the subunit mRNAs. In clear contrast, GAD67 mRNA was abundant in the outer half of the germinal matrix (i.e., TZ or SV), and in the intermediate zone as well. Immunocytochemical staining of E17 neocortex with anti-GABA antibody revealed a well defined band of GABA-immunoreactive cells and processes in the SV and occasional positive cells in the VZ. It appears that cells in the proliferative zone may express GABA at the migratory stage, whereas cells in the VZ may express mRNAs for GABAA receptor alpha 4, beta 1, and gamma 1 subunits at the premigratory stage, just after completing cell division.(ABSTRACT TRUNCATED AT 400 WORDS)
Multiple Components of Ca2+Channel Facilitation in Cerebellar Granule Cells: Expression of Facilitation during Development in Culture
Authors: Parri H. Rheinallt , Lansman Jeffry B.
Published: April 2018

The contribution of pharmacologically distinct Ca2+channels to prepulse-induced facilitation was studied in mouse cerebellar granule cells. Ca2+channel facilitation was measured as the percentage increase in the whole-cell current recorded during a test pulse before and after it was paired with a positive prepulse. The amount of facilitation was small in recordings made during the first few days in tissue culture but increased substantially after 1 week. L-type channels accounted for the largest proportion of facilitation in 1-week-old cells (60–70%), whereas N-type channels contributed very little (∼3%). The toxins ω-agatoxin IVa or ω-conotoxin MVIIC (after block of N-, L-, and P-type channels) each blocked a small percentage of facilitation (∼12 and 14%, respectively). Perfusion of cells with GTP-γ-S enhanced the facilitation of N-type channels, whereas it inhibited facilitation of L-type channels. During developmentin vitro, the contribution of L-type channels to the whole-cell current decreased. Single-channel recordings showed the presence of 10 and 15 pS L-type Ca2+channels in 1-d-old cells. After 1 week in culture, a ∼25 pS L-type channel dominated recordings from cell-attached patches. Positive prepulses increased the activity of the 25 pS channel but not of the smaller conductance channels. The expression of Ca2+channel facilitation during development may contribute to changes in excitability that allow frequency-dependent Ca2+influx during the period of active synaptogenesis.
Myomodulin Gene ofLymnaea: Structure, Expression, and Analysis of Neuropeptides
Authors: Kellett Elaine , Perry Stephen J. , Santama Niovi , Worster Belinda M. , Benjamin Paul R. , Burke Julian F.
Published: April 2018

The myomodulin family of neuropeptides is an important group of neural cotransmitters in molluscs and is known to be present in the neural network that controls feeding behavior in the snailLymnaea. Here we show that a single gene encodes five structurally similar forms of myomodulin: GLQMLRLamide, QIPMLRLamide, SMSMLRLamide, SLSMLRLamide, and PMSMLRLamide, the latter being present in nine copies. Analysis of the organization of the gene indicates that it is transcribed as a single spliced transcript from an upstream promoter region that contains multiple cAMP-responsive elements, as well as putative elements with homology to tissue-specific promoter-binding sites. The presence in nervous tissue of two of the peptides, GLQMLRLamide and PMSMLRLamide, is confirmed by mass spectrometry.In situhybridization analysis indicates that the gene is expressed in specific cells in all ganglia of the CNS ofLymnaea, which will allow physiological analysis of the function of myomodulins at the level of single identified neurons.
Multiple Actions of 1S,3R-ACPD in Modulating Endogenous Synaptic Transmission to Spinal Respiratory Motoneurons
Authors: Dong Xiao-Wei , Morin Didier , Feldman Jack L.
Published: April 2018

To determine physiological roles of metabotropic glutamate receptors (mGluRs) affecting breathing, we examined the effects of (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) on synaptic transmission and excitability of phrenic motoneurons (PMNs) in anin vitroneonatal rat brainstem/spinal cord preparation. The effects of 1S,3R-ACPD were multiple, including reduction of inspiratory-modulated synaptic currents and increase of neuronal excitability via an inward current (Iacpd) associated with a decrease of membrane conductance. The mechanism underlying synaptic depression was examined. We found that 1S,3R-ACPD reduced the frequency but not the amplitude of miniature excitatory postsynaptic currents. The current induced by exogenous AMPA was not significantly affected by 1S,3R-ACPD. These results suggest that 1S,3R-ACPD-induced reduction of inspiratory synaptic currents is mediated by presynaptic mGluRs. We also examined the ionic basis forIacpd. We found thatIacpdhad a reversal potential of approximately −100 mV, close to the estimatedEK+(−95 mV). Elevating extracellular [K+] to 9 mmreduced theIacpdreversal potential to −75 mV. The K+channel blocker Ba2+induced an inward current with a reversal potential at −93 mV associated with a decrease of membrane conductance, closely resembling the effect of 1S,3R-ACPD. Moreover, Ba2+occluded 1S,3R-ACPD effects. In the presence of Ba2+,Iacpdand the 1S,3R-ACPD-induced decrease of membrane conductance were diminished. Our data indicate that the dominant component ofIacpdresults from the blockade of a Ba2+-sensitive resting K+conductance. We conclude that the activation of mGluRs affects the inspiratory-modulated activity of PMNs via distinct mechanisms at pre- and postsynaptic sites.
Hippocampal AstrocytesIn SituRespond to Glutamate Released from Synaptic Terminals
Authors: Porter James T. , McCarthy Ken D.
Published: April 2018

A long-standing question in neurobiology is whether astrocytes respond to the neuronal release of neurotransmittersin vivo. To address this question, acutely isolated hippocampal slices were loaded with the calcium-sensitive dye Calcium Green-1 and the responses of the astrocytes to electrical stimulation of the Schaffer collaterals were monitored by confocal microscopy. To confirm that the responsive cells were astrocytes, the slices were immunostained for the astrocytic marker glial fibrillary acidic protein. Stimulation of the Schaffer collaterals (50 Hz, 2 sec) resulted in increases in the concentration of intracellular calcium ([Ca2+]i) in the astrocytes located in the stratum radiatum of CA1. The astrocytic responses were blocked by the sodium channel blocker tetrodotoxin, the voltage-dependent calcium channel blocker ω-conotoxin-MVIIC, and the selective metabotropic glutamate receptor antagonist α-methyl-4-carboxyphenylglycine (MCPG). These results suggest that the astrocytic responses were induced by stimulation of metabotropic glutamate receptors on the astrocytes by neuronally released glutamate. The astrocytic responses to neuronal stimulation were enhanced in the presence of the K+channel antagonist 4-aminopyridine (4-AP). Inhibition of the astrocytic responses in the presence of 4-AP required the presence of both MCPG and the ionotropic glutamate receptor antagonist kynurenic acid. These results suggest that higher levels of neuronal activity result in stimulation of both metabotropic and ionotropic glutamate receptors on the astrocytes. Overall, the results indicate that hippocampal astrocytesin situare able to respond to the neuronal release of the neurotransmitter glutamate with increases in [Ca2+]i.
Oligodendroglia Regulate the Regional Expansion of Axon Caliber and Local Accumulation of Neurofilaments during Development Independently of Myelin Formation
Authors: Sánchez Ivelisse , Hassinger Linda , Paskevich Peter A. , Shine H. David , Nixon Ralph A.
Published: April 2018

Axon caliber may be influenced by intrinsic neuronal factors and extrinsic factors related to myelination. To understand these extrinsic influences, we studied how axon-caliber expansion is related to changes in neurofilament and microtubule organization as axons of retinal ganglion cells interact with oligodendroglia and become myelinated during normal mouse brain development. Caliber expanded and neurofilaments accumulated only along regions of the axon invested with oligodendroglia. Very proximal portions of axons within a region of the optic nerve from which oligodendrocytes are excluded remained unchanged. More distally, these axons rapidly expanded an average of fourfold as soon as they were recruited to become myelinated between postnatal days 9 and 120. Unmyelinated axons remained unchanged. Axons ensheathed by oligodendroglial processes, but not yet myelinated, were intermediate in caliber and neurofilament number. That oligodendrocytes can trigger regional caliber expansion in the absence of myelin was confirmed using three strains of mice with different mutations that prevent myelin formation but allow wrapping of some axons by oligodendroglial processes. Unmyelinated axons persistently wrapped by oligodendrocytes showed full axon caliber expansion, neurofilament accumulation, and appropriately increased lateral spacing between neurofilaments. Thus, signals from oligodendrocytes, independent of myelin formation, are sufficient to induce full axon radial growth primarily by triggering local accumulation and reorganization of the neurofilament network.
Actions of Substance P on Rat Neostriatal NeuronsIn Vitro
Authors: Aosaki Toshihiko , Kawaguchi Yasuo
Published: April 2018

Actions of substance P (SP) on the neostriatal neurons inin vitrorat slice preparations were studied via whole-cell patch-clamp recording. Almost all large aspiny neurons (cholinergic cells) and half of the low-threshold spike (LTS) cells (somatostatin/NOS-positive cells) showed depolarization or an inward shift of the holding currents in response to bath-applied SP in a dose-dependent manner. In contrast, no responses were observed in fast-spiking (FS) cells (parvalbumin-positive cells) and medium spiny cells. Spike discharges followed by slow EPSPs/EPSCs were evoked by intrastriatal electrical stimulation in the large aspiny neurons. Pretreatment with [d-Arg1,d-Pro2,d-Trp7,9,Leu11]-SP, an antagonist of the SP receptor, reversibly suppressed the induction of the slow EPSPs/EPSCs and unmasked slow IPSCs. The SP-induced inward current, although almost unchanged even after the blockade ofIhchannels and voltage-dependent Na+, Ca2+, and K+channels, changed its amplitude according to the Na+concentration used in both the large aspiny neurons and LTS cells. Thus, the cation current could account for virtually all of the inward current at resting levels in both neurons. These results suggest that the firing of afferent neurons such as striatonigral medium spiny neurons, one of the possible sources of SP, would increase the firing probability of the two types of interneurons of the neostriatum by SP-receptor-mediated opening of tetrodotoxin-insensitive cation channels.
Implants of Encapsulated Human CNTF-Producing Fibroblasts Prevent Behavioral Deficits and Striatal Degeneration in a Rodent Model of Huntington’s Disease
Authors: Emerich Dwaine F. , Lindner Mark D. , Winn Shelley R. , Chen Er-Yun , Frydel Beata R. , Kordower Jeffrey H.
Published: April 2018

Delivery of neurotrophic molecules to the CNS has gained considerable attention as a potential treatment strategy for neurological disorders. In the present study, a DHFR-based expression vector containing the human ciliary neurotrophic factor (hCNTF) was transfected into a baby hamster kidney fibroblast cell line (BHK). Using a polymeric device, encapsulated BHK-control cells and those secreting hCNTF (BHK-hCNTF) were transplanted unilaterally into the rat lateral ventricle. Twelve days later, the same animals received unilateral injections of quinolinic acid (QA; 225 nmol) into the ipsilateral striatum. After surgery, animals were behaviorally tested for apomorphine-induced rotation behavior and for skilled forelimb function using the staircase test. Rats receiving BHK-hCNTF cells rotated significantly less than animals receiving BHK-control cells. No behavioral effects of hCNTF were observed on the staircase test. Nissl-stained sections demonstrated that BHK-hCNTF cells significantly reduced the extent of striatal damage produced by QA. Quantitative analysis of striatal neurons further demonstrated that both choline acetyltransferase- and GAD-immunoreactive neurons were protected by BHK-hCNTF implants. In contrast, a similar loss of NADPH-diaphorase-positive cells was observed in the striatum of both implant groups. Analysis of retrieved capsules revealed numerous viable and mitotically active BHK cells that continued to secrete hCNTF. These results support the concepts that implants of polymer-encapsulated hCNTF-releasing cells can be used to protect striatal neurons from excitotoxic damage and that this strategy may ultimately prove relevant for the treatment of Huntington’s disease.
Synchronous Activity in Locus Coeruleus Results from Dendritic Interactions in Pericoerulear Regions
Authors: Ishimatsu Masaru , Williams John T.
Published: April 2018

Locus coeruleus (LC) neurons in brain slices from adult rats were studied using intracellular and extracellular recordings to investigate synchronous activity. Spontaneous field potentials were recorded with extracellular electrodes in solutions containing tetraethylammonium chloride (10 mm) and BaCl2(1 mm). These field potentials were found throughout but not outside the LC cell body region. No field potentials were observed in control solutions. Paired recordings showed that field potentials were synchronous in all areas of the LC. The synchronous activity was resistant to tetrodotoxin (1 μm) and to the neurotransmitter receptor blockersd-2-amino-5-phosphonopentanoic acid, bicuculline, 6-cyano-7-nitroquinoxaline-2,3-dione, idazoxan, and strychnine, suggesting that this activity was not synaptically driven. Field potentials were also synchronous with oscillations in membrane potential recorded with intracellular electrodes. The oscillations in membrane potential were 5–30 mV in amplitude and had a biphasic waveform. Neither the frequency nor the waveform of the oscillations was dependent on the membrane potential. The glycyrrhetinic acid derivative carbenoxolone and intracellular acidification with CO2disrupted synchronous activity, suggesting a role of electrotonic coupling. When the cell body region of the LC was isolated from the pericoerulear dendritic regions by sectioning the slice rostral and caudal to the cell body region, synchronous activity was reduced or abolished. Dendritic interaction in the pericoerulear region was also indicated by improved voltage control of the opioid-induced potassium current, as indicated by a shift in the reversal potential to the potassium equilibrium potential. The results suggest that electrical interactions between dendrites outside the cell body region can account for synchronous activity within the nucleus.
Differential Sensitivity of Human Visual Cortex to Faces, Letterstrings, and Textures: A Functional Magnetic Resonance Imaging Study
Authors: Puce Aina , Allison Truett , Asgari Maryam , Gore John C. , McCarthy Gregory
Published: April 2018

Twelve normal subjects viewed alternating sequences of unfamiliar faces, unpronounceable nonword letterstrings, and textures while echoplanar functional magnetic resonance images were acquired in seven slices extending from the posterior margin of the splenium to near the occipital pole. These stimuli were chosen to elicit initial category-specific processing in extrastriate cortex while minimizing semantic processing. Overall, faces evoked more activation than did letterstrings. Comparing hemispheres, faces evoked greater activation in the right than the left hemisphere, whereas letterstrings evoked greater activation in the left than the right hemisphere. Faces primarily activated the fusiform gyrus bilaterally, and also activated the right occipitotemporal and inferior occipital sulci and a region of lateral cortex centered in the middle temporal gyrus. Letterstrings primarily activated the left occipitotemporal and inferior occipital sulci. Textures primarily activated portions of the collateral sulcus. In the left hemisphere, 9 of the 12 subjects showed a characteristic pattern in which faces activated a discrete region of the lateral fusiform gyrus, whereas letterstrings activated a nearby region of cortex within the occipitotemporal and inferior occipital sulci. These results suggest that different regions of ventral extrastriate cortex are specialized for processing the perceptual features of faces and letterstrings, and that these regions are intermediate between earlier processing in striate and peristriate cortex, and later lexical, semantic, and associative processing in downstream cortical regions.
Developmental Expression of Platelet-Derived Growth Factor α-Receptor in Neurons and Glial Cells of the Mouse CNS
Authors: Oumesmar Brahim Nait , Vignais Lionel , Baron-Van Evercooren Anne
Published: April 2018

The synthesis of platelet-derived growth factor-α receptor (PDGF-αR) is commonly attributed to oligodendrocyte progenitors during late embryonic and postnatal development. However, we recently demonstrated that mature neurons could also synthesize PDGF-αR, emphasizing a larger role for this receptor than previously described. In the present study, to analyze the pattern of PDGF-αR expression during postnatal development of the mouse CNS, we usedin situhybridization and immunohistochemistry on brain and spinal cord tissue sections. We found that, in addition to immature cells of the oligodendrocyte lineage, neurons of various CNS regions express PDGF-αR transcripts and protein as early as postnatal day 1 (P1). Whereas neuronal expression was maintained at all ages, the oligodendroglial expression strongly decreased after P21. In the adult, PDGF-αR was detected in very few oligodendrocyte progenitors scattered in the cerebral cortex or in white matter tracts, thus suggesting the presence of PDGF-αR on O-2Aadultprogenitors. In the mature CNS, PDGF-αR transcripts and protein were mainly localized in neurons of numerous structures, such as the olfactory bulb, cerebral cortex, hippocampus, and brainstem nuclei and in motor neurons of the ventral horn of the spinal cord. The differential expression of PDGF-αR in oligodendroglia and neurons argues in favor of several roles of PDGF during development.
GDNF Reduces Drug-Induced Rotational Behavior after Medial Forebrain Bundle Transection by a Mechanism Not Involving Striatal Dopamine
Authors: Tseng Jack L. , Baetge E. Edward , Zurn Anne D. , Aebischer Patrick
Published: April 2018

Parkinson’s disease (PD) is characterized by the progressive loss of the substantia nigra (SN) dopaminergic neurons projecting to the striatum. Neurotrophic factors may have the potential to prevent or slow down the degenerative process occurring in PD. To that end, we examined whether low amounts of glial cell line-derived neurotrophic factor (GDNF) continuously released from polymer-encapsulated genetically engineered cells are able to prevent the loss of tyrosine hydroxylase immunoreactivity (TH-IR) in SN neurons and ameliorate the amphetamine-induced rotational asymmetry in rats that have been subjected to a unilateral medial forebrain bundle (MFB) axotomy. Baby hamster kidney (BHK) cells transfected with the cDNA for GDNF were encapsulated in a polymer fiber and implanted unilaterally at a location lateral to the MFB and rostral to the SN. ELISA assays before implantation show that the capsules release ∼5 ng of GDNF/capsule per day. One week later, the MFB was axotomized unilaterally ipsilateral to the capsule placement. Seven days later, the animals were tested for amphetamine-induced rotational asymmetry and killed. The striatum was excised and analyzed either for catecholamine content or TH-IR, while the SN was immunostained for the presence of TH-IR. GDNF did not prevent the loss of dopamine in the striatum. However, GDNF significantly rescued TH-IR neurons in the SN pars compacta. Furthermore, GDNF also significantly reduced the number of turns per minute ipsilateral to the lesion under the influence of amphetamine. Improvement of rotational behavior in the absence of dopaminergic striatal reinnervation may reflect neuronal plasticity in the SN, as suggested by the dendritic sprouting observed in animals receiving GDNF. These results illustrate that the continuous release of low levels of GDNF close to the SN is capable of protecting the nigral dopaminergic neurons from an axotomy-induced lesion and significantly improving pharmacological rotational behavior by a mechanism other than dopaminergic striatal reinnervation.
Mechanosensory Neurons InnervatingAplysiaSiphon Encode Noxious Stimuli and Display Nociceptive Sensitization
Authors: Illich Paul A. , Walters Edgar T.
Published: April 2018

Numerous studies of learning and memory inAplysiahave focused on primary mechanosensory neurons innervating the siphon and having their somata in the left E (LE) cluster of the abdominal ganglion. Although systematic analyses have been made of the responses of these LE cells to mechanical stimulation of the tightly pinned siphon, little is known about corresponding responses when the siphon is unrestrained. The present study demonstrates that LE mechanosensory thresholds in the freely moving siphon are much higher than in the pinned siphon. Light tactile stimuli adequate to activate central neurons and reflexive siphon movements often fail to activate the LE cells when the siphon is unrestrained. Because the LE cells display increasing discharge to increasing pressures, with maximal activation by crushing or tearing stimuli that cause tissue injury, they satisfy accepted definitions of nociceptor. Indeed, they show similarities to vertebrate Aδ nociceptors, including a property apparently unique (among primary afferents) to nociceptors—sensitization by noxious stimulation of their receptive field. Either pinching or pinning the siphon decreases LE cell mechanosensory threshold and enhances soma excitability. Such stimuli reduce effective tissue compliance and cause neuromodulation that enhances sensory responsiveness. These results, and recent descriptions of predatory attacks onAplysia, suggest that LE sensory neurons are tuned to grasping and crushing stimuli that threaten or produce bodily harm. LE cell sensitization has effects, resembling hyperalgesia and allodynia, that compensate for loss of sensory function during injury and help protect against subsequent threats.
Nitric Oxide Involvement inHydra vulgarisVery Primitive Olfactory-Like System
Authors: Colasanti Marco , Venturini Giorgio , Merante Angelo , Musci Giovanni , Lauro Giuliana M.
Published: April 2018

Hydra feeding response is a very primitive olfactory-like behavior present in a multicellular organism. We investigated the role of nitric oxide (NO) in the induction and control of hydra feeding response. Under basal conditions, hydra specimens produce detectable amounts of nitrite (NO2−), the breakdown product of NO. When hydra were incubated with reduced glutathione (GSH), the typical activator of feeding response, an increase of basal NO production was observed. This effect was inhibited by glutamic or α-aminoadipic acids, two GSH antagonists, which block GSH-induced feeding response, and by the NO synthase (NOS) inhibitorl-NAME. Moreover, we found that hydra possess a calcium-dependent (but calmodulin-independent) NOS isoform. By using exogenous NO donors and NOS inhibitors, we demonstrated that NO stimulus can participate both in triggering tentacular movements and in recruiting neighbor tentacles during hydra feeding response. By using dbt2-cGMP, an analog to cGMP, we observed that the NO effect was independent of cGMP pathway. Our results strongly implicate NO involvement in hydra very primitive feeding behavior, thus confirming its preservation throughout evolution.
Myoclonic Epilepsy and Ragged Red Fibers (MERRF) Syndrome: Selective Vulnerability of CNS Neurons Does Not Correlate with the Level of Mitochondrial tRNAlysMutation in Individual Neuronal Isolates
Authors: Zhou Li , Chomyn Anne , Attardi Giuseppe , Miller Carol A.
Published: April 2018

Selective vulnerability of subpopulations of neurons is a striking feature of neurodegeneration. Mitochondrially transmitted diseases are no exception. In this study CNS tissues from a patient with myoclonus epilepsy and ragged red fibers (MERRF) syndrome, which results from an A to G transition of nucleotide (nt) 8344 in the mitochondrial tRNALysgene, were examined for the proportion of mutant mtDNA. Either individual neuronal somas or the adjacent neuropil and glia were microdissected from cryostat tissue sections of histologically severely affected brain regions, including dentate nuclei, Purkinje cells, and inferior olivary nuclei, and from a presumably less affected neuronal subpopulation, the anterior horn cells of the spinal cord. Mutant and normal mtDNA were quantified after PCR amplification with a mismatched primer and restriction enzyme digestion. Neurons and the surrounding neuropil and glia from all CNS regions that were analyzed exhibited high proportions of mutant mtDNA, ranging from 97.6 ± 0.7% in Purkinje cells to 80.6 ± 2.8% in the anterior horn cells. Within each neuronal group that was analyzed, neuronal soma values were similar to those in the surrounding neuropil and glia or in the regional tissue homogenate. Surprisingly, as compared with controls, neuronal loss ranged from 7% of the Purkinje cells to 46% of the neurons of the dentate nucleus in MERRF cerebellum. Thus, factors other than the high proportion of mutant mtDNA, in particular nuclear-controlled neuronal differences among various regions of the CNS, seem to contribute to the mitochondrial dysfunction and ultimate cell death.
Intracellular Calcium Oscillations in Astrocytes: A Highly Plastic, Bidirectional Form of Communication between Neurons and AstrocytesIn Situ
Authors: Pasti Lucia , Volterra Andrea , Pozzan Tullio , Carmignoto Giorgio
Published: April 2018

The spatial–temporal characteristics of intracellular calcium ([Ca2+]i) changes elicited in neurons and astrocytes by various types of stimuli were investigated by means of confocal fluorescent microscopy in acute rat brain slices loaded with the Ca2+indicator indo-1. Neurons and astrocytes from the visual cortex and CA1 hippocampal region were identifiedin situon the basis of their morphological, electrophysiological, and pharmacological features. We show here that stimulation of neuronal afferents triggered periodic [Ca2+]ioscillations in astrocytes. The frequency of these oscillations was under a dynamic control by neuronal activity as it changed according to the pattern of stimulation. After repetitive episodes of neuronal stimulation as well as repetitive stimulation with a metabotropic glutamate receptor agonist, astrocytes displayed a long-lasting increase in [Ca2+]ioscillation frequency. Oscillating astrocytes were accompanied by repetitive [Ca2+]ielevations in adjacent neurons, most likely because of the release of glutamate via a tetanus toxin-resistant process. These results reveal that [Ca2+]ioscillations in astrocytes represent a highly plastic signaling system that underlies the reciprocal communication between neurons and astrocytes.
Both Neuropeptide Y and Serotonin Are Necessary for Entrainment of Circadian Rhythms in Mice by Daily Treadmill Running Schedules
Authors: Marchant Elliott G. , Watson Neil V. , Mistlberger Ralph E.
Published: April 2018

This study investigated the role of the suprachiasmatic nucleus (SCN) circadian pacemaker and its neuropeptide Y (NPY) and serotonin (5-HT) afferents in entrainment (synchronization) of mouse circadian rhythms by treadmill running. Blind C57BL/6j mice were run in treadmills for 3 hr/d for 3–10 weeks after receiving radio-frequency lesions of the SCN or the intergeniculate leaflet (IGL, the source of SCN NPY) or infusions of the 5-HT neurotoxin 5,7-DHT into the SCN area. Of 25 intact mice, 22 entrained and three showed period (τ, the mean duration of the circadian cycle) modulations to scheduled running. Arrhythmic SCN-ablated mice did not synchronize to scheduled running in a way suggestive of circadian pacemaker mediation. Of 15 mice with IGL lesions, only two with partial lesions entrained. Mice with complete IGL lesions (five), confirmed by immunocytochemistry, showed no entrainment or τ changes. Of 19 mice with 5-HT lesions, only two with partial lesions entrained. All but two mice with complete (10) or nearly complete (4) 5-HT denervation, confirmed by immunocytochemistry, showed τ modulations during the treadmill schedule. Failure to entrain was not explained by group differences in τ before the treadmill schedules. The results indicate that the SCN and both NPY and 5-HT are necessary for entrainment to 24 hr schedules of forced running but that complete loss of 5-HT does not prevent modulations of pacemaker motion by behavioral stimuli. Treadmill entrainment in mice may involve synergistic interactions between 5-HT and NPY afferents at some site within the circadian system.
Long-Term Potentiation in the Hippocampal CA1 Region of Mice Lacking cGMP-Dependent Kinases Is Normal and Susceptible to Inhibition of Nitric Oxide Synthase
Authors: Kleppisch Thomas , Pfeifer Alexander , Klatt Peter , Ruth Peter , Montkowski Alexandra , Fässler Reinhard , Hofmann Franz
Published: April 2018

Long-term potentiation (LTP) is a potential cellular mechanism for learning and memory. The retrograde messenger nitric oxide (NO) is thought to induce LTP in the CA1 region of the hippocampus via activation of soluble guanylyl cyclase (sGC) and, ultimately, cGMP-dependent protein kinase (cGK). Two genes code for the isozymes cGKI and cGKII in vertebrates. The functional role of cGKs in LTP was analyzed using mice lacking the gene(s) for cGKI, cGKII, or both. LTP was not altered in the mutant mice lineages. However, LTP was reduced by inhibition of NO synthase and NMDA receptor antagonists, respectively. The reduced LTP was not recovered by the cGK-activator 8-(4 chlorophenylthio)-cGMP. Moreover, LTP was not affected by the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]-quiloxalin-1-one. In contrast, it was effectively suppressed by nicotinamide, a blocker of the ADP-ribosyltransferase. These results show that cGKs are not involved in LTP in mice and that NO induces LTP through an alternative cGMP-independent pathway, possibly ADP-ribosylation.