bluuebunny/crossref_metadata_2025 huggingface dataset:
Somatodendritic Depolarization-Activated Potassium Currents in Rat Neostriatal Cholinergic Interneurons Are Predominantly of the A Type and Attributable to Coexpression of Kv4.2 and Kv4.1 Subunits
Authors: Song W.-J. , Tkatch T. , Baranauskas G. , Ichinohe N. , Kitai S. T. , Surmeier D. J.
Published: April 2018

Unlike other neostriatal neurons, cholinergic interneurons exhibit spontaneous, low-frequency, repetitive firing. To gain an understanding of the K+channels regulating this behavior, acutely isolated adult rat cholinergic interneurons were studied using whole-cell voltage-clamp and single-cell reverse transcription-PCR techniques. Cholinergic interneurons were identified by the presence of choline acetyltransferase (ChAT) mRNA. Depolarization-activated potassium currents in cholinergic interneurons were dominated by a rapidly inactivating, K+-selective A current that became active at subthreshold potentials. Depolarizing prepulses inactivated this component of the current, leaving a delayed, rectifier-like current. Micromolar concentrations of Cd2+dramatically shifted the voltage dependence of the A current without significantly affecting the delayed rectifier. The A-channel antagonist 4-aminopyridine (4-AP) produced a voltage-dependent block (IC50, ∼1 mm) with a prominent crossover at millimolar concentrations. On the other hand, TEA preferentially blocked the sustained current component at concentrations <10 mm. Single-cell mRNA profiling of subunits known to give rise to rapidly inactivating K+currents revealed the coexpression of Kv4.1, Kv4.2, and Kv1.4 mRNAs but low or undetectable levels of Kv4.3 and Kv3.4 mRNAs. Kv1.1, β1, and β2 subunit mRNAs, but not β3, were also commonly detected. The inactivation recovery kinetics of the A-type current were found to match those of Kv4.2 and 4.1 channels and not those of Kv1.4 or Kv1.1 and β1 channels. Immunocytochemical analysis confirmed the presence of Kv4.2 but not Kv1.4 subunits in the somatodendritic membrane of ChAT-immunoreactive neurons. These results argue that the depolarization-activated somatodendritic K+currents in cholinergic interneurons are dominated by Kv4.2- and Kv4.1-containing channels. The properties of these channels are consistent with their playing a prominent role in governing the slow, repetitive discharge of interneurons seenin vivo.
Light-Induced Retinal Degeneration Suppresses Developmental Progression of Flip-to-Flop Alternative Splicing in GluR1
Authors: Harada Takayuki , Harada Chikako , Sekiguchi Masayuki , Wada Keiji
Published: April 2018

AMPA receptors are hetero-oligomers composed of subsets of four distinct subunits, termed GluR1, GluR2, GluR3, and GluR4. Using quantitative reverse transcription-PCR analysis, we have found that light-induced degeneration of rat retina dramatically suppresses developmental progression of the flip-to-flop alternative splicing switch of retinal GluR1 mRNA. When animals were raised under standard conditions of a 12 hr light/dark cycle (LD 12:12), the flop-to-flip ratio in GluR1 and GluR2 dramatically increased between postnatal day 10 (P10) and P28, and the ratios continued to increase gradually up to P84. When animals were raised in complete darkness, this increase was delayed in GluR1 between P21 and P42. In addition, the increase of the flop-to-flip ratio in GluR1 was strongly suppressed after P21 under conditions of continuous illumination from P2. This is significant because P21 is just after the eye opening and is the timing of the onset of light-induced retinal degeneration. This suppression of the increase of the flop-to-flip ratio was specific to GluR1 and was not observed in GluR2–4. Immunocytochemistry and immunoblot analysis suggested no changes in either the distribution or expression of GluR1 protein in the light-damaged retina measured at P84. When rats were raised under continuous illumination from P2 to P21 followed by LD 12:12 from P22 to P84, retinal degeneration did not progress after P22. In such animals the flop-to-flip ratio, once decreased to ∼50% of the control (LD 12:12) at P21, was restored to the control level at P84. These findings demonstrate that developmental progression of the flip-to-flop exon switch in retinal GluR1 is affected by lighting conditions, and that light-induced retinal degeneration contributes to the mechanism of suppression of this splicing switch.
Brain-Derived Neurotrophic Factor Modulates the Development of the Dopaminergic Network in the Rodent Retina
Authors: Cellerino Alessandro , Pinzón-Duarte Germán , Carroll Patrick , Kohler Konrad
Published: April 2018

Dopaminergic cells in the retina express the receptor for brain-derived neurotrophic factor (BDNF) (Cellerino and Kohler, 1997). To investigate whether BDNF can influence the development of the retinal dopaminergic pathway, we performed intraocular injections of BDNF during the second or third postnatal week and visualized the dopaminergic system with tyrosine hydroxylase (TH) immunohistochemistry. Both regimens of BDNF treatment caused an increase in TH immunoreactivity in stratum 1 and stratum 3 of the inner plexiform layer (IPL). D2 dopamine receptor immunoreactivity, a presynaptic marker of dopaminergic cells (Veruki, 1996), was also increased in stratum 1 and stratum 3 of the inner plexiform layer. These data suggest that BDNF causes sprouting of dopaminergic fibers in the inner plexiform layer. Other neurochemical systems, for example, the cholinergic amacrine cells, remained unaffected. Similar effects were observed after injections of neurotrophin-3 and neurotrophin-4, but not nerve growth factor. Analysis of whole-mounted TH-immunolabeled retinae revealed hypertrophy of dopaminergic cells (+41% in soma areas;p< 0.01) and an increase of labeled dopaminergic varicosities in stratum 1 of the IPL (+51%;p< 0.01) after BDNF treatment. The opposite was observed in mice homozygous for a null mutation of thebdnfgene: dopaminergic cells were atrophic (−22.5% in soma areas;p< 0.05), and the density of TH-positive varicosities in stratum 1 was reduced (57%;p< 0.01). We conclude that BDNF controls the development of the retinal dopaminergic network and may be particularly important in determining the density of dopaminergic innervation in the retina.
Time-Dependent Reversal of Long-Term Potentiation by an Integrin Antagonist
Authors: Stäubli Ursula , Chun Daniel , Lynch Gary
Published: April 2018

The integrin antagonist Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) was applied by local ejection to one of two recording sites in hippocampal slices at various times before and after long-term potentiation (LTP) was induced at both sites with theta burst stimulation. Applications 10 min before, immediately after, and 10 min after induction caused LTP at the experimental site to decay steadily relative to that at the within-slice control site. However, application at 25 min or more after induction had no detectable effect on potentiation. Similar results were obtained when the integrin antagonist was perfused into the slice rather than applied locally. The time period after induction during which GRGDSP interfered with LTP consolidation corresponds to that during which LTP is susceptible to reversal by low-frequency afferent stimulation and newly formed memories are vulnerable to various disruptive treatments. Comparable experiments using a peptide that blocks an extracellular binding site of neural cell adhesion molecules (NCAMs) did not yield time-dependent reversal of LTP; i.e., an antagonist that interacts with the fourth immunoglobulin-like domain reduced LTP when applied before induction but not afterward. Moreover, LTP formation occurred normally in the presence of an antibody against the fibronectin repeat domain of NCAM. These results suggest that integrin activation and signaling occurring over several minutes after LTP induction are necessary for stabilizing synaptic potentiation and by inference may be required for the conversion of new memories into a not readily disrupted state.
Galanin Receptor-Mediated Inhibition of Glutamate Release in the Arcuate Nucleus of the Hypothalamus
Authors: Kinney Gregory A. , Emmerson Paul J. , Miller Richard J.
Published: April 2018

It is thought that galanin, a 29 amino acid neuropeptide, is involved in various neuronal functions, including the regulation of food intake and hormone release. Consistent with this idea, galanin receptors have been demonstrated throughout the brain, with high levels being observed in the hypothalamus. However, little is known about the mechanisms by which galanin elicits its actions in the brain. Therefore, we studied the effects of galanin and its analogs on synaptic transmission using anin vitroslice preparation of rat hypothalamus. In arcuate nucleus neurons, application of galanin resulted in an inhibition of evoked glutamatergic EPSCs and a decrease in paired-pulse depression, indicating a presynaptic action. The fragments galanin 1–16 and 1–15 produced a robust depression of synaptic transmission, whereas the fragment 3–29 produced a lesser degree of depression. The chimeric peptides C7, M15, M32, and M40, which have been reported to antagonize some actions of galanin, all produced varying degrees of depression of evoked EPSCs. In a minority of cases, C7, M15, and M40 antagonized the actions of galanin. Analysis of mEPSCs in the presence of TTX and Cd2+, or after application of α-latrotoxin, indicated a site of action for galanin downstream of Ca2+entry. Thus, our data suggest that galanin acts via several subtypes of presynaptic receptors to depress synaptic transmission in the rat arcuate nucleus.
The Glutamate Transporter EAAT4 in Rat Cerebellar Purkinje Cells: A Glutamate-Gated Chloride Channel Concentrated near the Synapse in Parts of the Dendritic Membrane Facing Astroglia
Authors: Dehnes Yvette , Chaudhry Farrukh A. , Ullensvang Kyrre , Lehre Knut P. , Storm-Mathisen Jon , Danbolt Niels C.
Published: April 2018

Antibodies to an excitatory amino acid transporter (EAAT4) label a glycoprotein of ∼65 kDa strongly in the cerebellum and weakly in the forebrain. Cross-linking of cerebellar proteins with bis(sulfosuccinimidyl) suberate before solubilization causes dimer bands of EAAT4 and both dimer and trimer bands of the other glutamate transporters GLAST (EAAT1) and GLT (EAAT2) to appear on immunoblots. In contrast to GLAST, GLT, and EAAC (EAAT3), EAAT4 is unevenly distributed in the cerebellar molecular layer, being strongly expressed in parasagittal zones. It is located in cerebellar Purkinje cells, and the highest concentrations are seen in ones expressing high levels of zebrin II (aldolase C). The labeling of Purkinje cell spines and thin dendrites is stronger than that of large diameter dendrites and cell bodies. EAAT4 is present at low concentrations in the synaptic membrane, but is highly enriched in the parts of the dendritic and spine membranes facing astrocytes (which express GLAST and GLT) compared with parts facing neuronal membranes, suggesting a functional relationship with glial glutamate transporters. The presence of EAAT4 in intracellular cisterns and multivesicular organelles may reflect turnover of transporter in the plasma membrane. The total Purkinje cell spine surface and the EAAT4 concentration were found to be 1.1 m2/cm3and 0.2 mg/cm3, respectively, in the molecular layer, corresponding to 1800 molecules/μm2. The juxtasynaptic location of EAAT4 may explain electrophysiological observations predicting the presence of a neuronal glutamate transporter near the release site at a Purkinje cell spine synapse. EAAT4 may function as a combined transporter and inhibitory glutamate receptor.
Long-Distance Axonal Regeneration in the Transected Adult Rat Spinal Cord Is Promoted by Olfactory Ensheathing Glia Transplants
Authors: Ramón-Cueto Almudena , Plant Giles W. , Avila Jesus , Bunge Mary Bartlett
Published: April 2018

The lack of axonal regeneration in the injured adult mammalian spinal cord leads to permanent functional impairment. To induce axonal regeneration in the transected adult rat spinal cord, we have used the axonal growth-promoting properties of adult olfactory bulb ensheathing glia (EG). Schwann cell (SC)-filled guidance channels were grafted to bridge both cord stumps, and suspensions of pure (98%) Hoechst-labeled EG were stereotaxically injected into the midline of both stumps, 1 mm from the edges of the channel. In EG-transplanted animals, numerous neurofilament-, GAP-43-, anti-calcitonin gene-related peptide (CGRP)-, and serotonin-immunoreactive fibers traversed the glial scars formed at both cord–graft interfaces. Supraspinal serotonergic axons crossed the transection gap through connective tissue bridges formed on the exterior of the channels, avoiding the channel interior. Strikingly, after crossing the distal glial scar, these fibers elongated in white and periaqueductal gray matter, reaching the farthest distance analyzed (1.5 cm). Tracer-labeled axons present in SC grafts were found to extend across the distal interface and up to 800 μm beyond in the distal cord. Long-distance regeneration (at least 2.5 cm) of injured ascending propriospinal axons was observed in the rostral spinal cord. Transplanted EG migrated longitudinally and laterally from the injection sites, reaching the farthest distance analyzed (1.5 cm). They moved through white matter tracts, gray matter, and glial scars, overcoming the inhibitory nature of the CNS environment, and invaded SC and connective tissue bridges and the dorsal and ventral roots adjacent to the transection site. Transplanted EG and regenerating axons were found in the same locations. Because EG seem to provide injured spinal axons with appropriate factors for long-distance elongation, these cells offer new possibilities for treatment of CNS conditions that require axonal regeneration.
Endocytotic Formation of Vesicles and Other Membranous Structures Induced by Ca2+and Axolemmal Injury
Authors: Eddleman Christopher S. , Ballinger Martis L. , Smyers Mark E. , Fishman Harvey M. , Bittner George D.
Published: April 2018

Vesicles and/or other membranous structures that form after axolemmal damage have recently been shown to repair (seal) the axolemma of various nerve axons. To determine the origin of such membranous structures, (1) we internally dialyzed isolated intact squid giant axons (GAs) and showed that elevation of intracellular Ca2+>100 μmproduced membranous structures similar to those in axons transected in Ca2+-containing physiological saline; (2) we exposed GA axoplasm to Ca2+-containing salines and observed that membranous structures did not form after removing the axolemma and glial sheath but did form in severed GAs after >99% of their axoplasm was removed by internal perfusion; (3) we examined transected GAs and crayfish medial giant axons (MGAs) with time-lapse confocal fluorescence microscopy and showed that many injury-induced vesicles formed by endocytosis of the axolemma; (4) we examined the cut ends of GAs and MGAs with electron microscopy and showed that most membranous structures were single-walled at short (5–15 min) post-transection times, whereas more were double- and multi-walled and of probable glial origin after longer (30–150 min) post-transection times; and (5) we examined differential interference contrast and confocal images and showed that large and small lesions evoked similar injury responses in which barriers to dye diffusion formed amid an accumulation of vesicles and other membranous structures. These and other data suggest that Ca2+inflow at large or small axolemmal lesions induces various membranous structures (including endocytotic vesicles) of glial or axonal origin to form, accumulate, and interact with each other, preformed vesicles, and/or the axolemma to repair the axolemmal damage.
Connexin32 Mutations Associated with X-Linked Charcot–Marie–Tooth Disease Show Two Distinct Behaviors: Loss of Function and Altered Gating Properties
Authors: Ressot Catherine , Gomès Danielle , Dautigny André , Pham-Dinh Danielle , Bruzzone Roberto
Published: April 2018

The X-linked form of Charcot–Marie–Tooth disease (CMTX) is associated with mutations in the gene encoding connexin32 (Cx32), which is expressed in Schwann cells. We have compared the functional properties of 11 Cx32 mutations with those of the wild-type protein by testing their ability to form intercellular channels in the paired oocyte expression system. Although seven mutations were functionally incompetent, four others were able to generate intercellular currents of the same order of magnitude as those induced by wild-type Cx32 (Cx32wt). In homotypic oocyte pairs, CMTX mutations retaining functional activity induced the development of junctional currents that exhibited changes in the sensitivity and kinetics of voltage dependence with respect to that of Cx32wt. The four mutations were also capable of interacting in heterotypic configuration with the wild-type protein, and in one case the result was a marked rectification of junctional currents in response to voltage steps of opposite polarity. In addition, the functional CMTX mutations displayed the same selective pattern of compatibility as Cx32wt, interacting with Cx26, Cx46, and Cx50 but failing to do so with Cx40. Although the functional mutations exhibited sensitivity to cytoplasmic acidification, which induced a ≥80% decrease in junctional currents, both the rate and extent of channel closure were enhanced markedly for two of them. Together, these results indicate that the functional consequences of CMTX mutations of Cx32 are of two drastically distinct kinds. The presence of a functional group of mutations suggests that a selective deficit of Cx32 channels may be sufficient to impair the homeostasis of Schwann cells and lead to the development of CMTX.
Characterization of Intrastriatal Recombinant Adeno-Associated Virus-Mediated Gene Transfer of Human Tyrosine Hydroxylase and Human GTP-Cyclohydrolase I in a Rat Model of Parkinson’s Disease
Authors: Mandel R. J. , Rendahl K. G. , Spratt S. K. , Snyder R. O. , Cohen L. K. , Leff S. E.
Published: April 2018

To achieve local, continuousl-DOPA delivery in the striatum by gene replacement as a model for a gene therapy for Parkinson’s disease, the present studies used high titer purified recombinant adeno-associated virus (rAAV) containing cDNAs encoding human tyrosine hydroxylase (hTH) or human GTP-cyclohydrolase I [GTPCHI, the rate-limiting enzyme for tetrahydrobiopterin (BH4) synthesis] or both to infect the 6-OHDA denervated rat striatum. Striatal TH and GTPCHI staining was observed 3 weeks after rAAV transduction, with little detectable perturbation of the tissue. Six months after intrastriatal rAAV transduction, TH staining was present but apparently reduced compared with the 3 week survival time. In a separate group of animals, striatal TH staining was demonstrated 1 year after rAAV transduction. Double staining studies using the neuronal marker NeuN indicated that >90% of rAAV-transduced cells expressing hTH were neurons. Microdialysis experiments indicated that only those lesioned animals that received the mixture of MD–TH and MD–GTPCHI vector displayed BH4independentin vivol-DOPA production (mean ∼4–7 ng/ml). Rats that received the hTH rAAV vector alone produced measurablel-DOPA (mean ∼1–4 ng/ml) only after receiving exogenous BH4.l-Aromatic amino acid decarboxylase blockade, but not 100 mmKCl-induced depolarization, enhancedl-DOPA overflow, and animals in the non-hTH groups (GTPCHI and alkaline phosphatase) yielded minimall-DOPA. Although elevatedl-DOPA was observed in animals that received mixed hTH and hGTPCHI rAAV vectors, there was no reduction of apomorphine-induced rotational behavior 3 weeks after intrastriatal vector injection. These data demonstrate that purified rAAV, a safe and nonpathogenic viral vector, mediates long-term striatal hTH transgene expression in neurons and can be used to successfully deliverl-DOPA to the striatum.
Axotomy Upregulates the Anterograde Transport and Expression of Brain-Derived Neurotrophic Factor by Sensory Neurons
Authors: Tonra James R. , Curtis Rory , Wong Vivien , Cliffer Kenneth D. , Park John S. , Timmes Andrew , Nguyen Trang , Lindsay Ronald M. , Acheson Ann , DiStefano Peter S.
Published: April 2018

In addition to the known retrograde transport of neurotrophins, it is now evident that endogenous brain-derived neurotrophic factor (BDNF) is transported in the anterograde direction in peripheral and central neurons. We used a double-ligation procedure that distinguishes between anterograde and retrograde flow to quantify the anterograde transport of endogenous neurotrophins and neuropeptides in the peripheral nervous system before and after axotomy. BDNF accumulation proximal to the ligation (anterograde transport) was twice that distal to the ligation (retrograde direction). Anterograde transport of nerve growth factor and neurotrophin-3 was not evident. Furthermore, BDNF anterograde transport increased 3.5-fold within 24 hr after sciatic nerve injury or dorsal rhizotomy. Anterograde transport of substance P and calcitonin gene-related peptide decreased after peripheral nerve lesion, demonstrating that there was no generalized increase in anterograde transport. To determine the source of the anterogradely transported BDNF, we performedin situhybridization in a variety of tissues before and after axotomy. Expression of BDNF mRNA in proximal nerve segments did not change with treatment, showing that the increased accumulation of BDNF was not a result of increased local synthesis. BDNF mRNA and protein were expressed by dorsal root ganglion sensory neurons but not by motor neurons. BDNF mRNA expression was increased 1 d after nerve injury, and BDNF protein was also increased twofold to threefold, suggesting that sensory neurons are the major contributing source of the increased BDNF traffic in the sciatic nerve. Our results suggest that increased anterogradely transported BDNF plays a role in the early neuronal response to peripheral nerve injury at sites distal to the cell body.
Neurturin Exerts Potent Actions on Survival and Function of Midbrain Dopaminergic Neurons
Authors: Horger Brian A. , Nishimura Merry C. , Armanini Mark P. , Wang Li-Chong , Poulsen Kris T. , Rosenblad Carl , Kirik Deniz , Moffat Barbara , Simmons Laura , Johnson Eugene , Milbrandt Jeff , Rosenthal Arnon , Bjorklund Anders , Vandlen Richard A. , Hynes Mary A. , Phillips Heidi S.
Published: April 2018

Glial cell line-derived neurotrophic factor (GDNF) exhibits potent effects on survival and function of midbrain dopaminergic (DA) neurons in a variety of models. Although other growth factors expressed in the vicinity of developing DA neurons have been reported to support survival of DA neuronsin vitro, to date none of these factors duplicate the potent and selective actions of GDNFin vivo. We report here that neurturin (NTN), a homolog of GDNF, is expressed in the nigrostriatal system, and that NTN exerts potent effects on survival and function of midbrain DA neurons. Our findings indicate that NTN mRNA is sequentially expressed in the ventral midbrain and striatum during development and that NTN exhibits survival-promoting actions on both developing and mature DA neurons.In vitro, NTN supports survival of embryonic DA neurons, andin vivo, direct injection of NTN into the substantia nigra protects mature DA neurons from cell death induced by 6-OHDA. Furthermore, administration of NTN into the striatum of intact adult animals induces behavioral and biochemical changes associated with functional upregulation of nigral DA neurons. The similarity in potency and efficacy of NTN and GDNF on DA neurons in several paradigms stands in contrast to the differential distribution of the receptor components GDNF Family Receptor α1 (GFRα1) and GFRα2 within the ventral mesencephalon. These results suggest that NTN is an endogenous trophic factor for midbrain DA neurons and point to the possibility that GDNF and NTN may exert redundant trophic influences on nigral DA neurons acting via a receptor complex that includes GFRα1.
Small Changes in Ambient Temperature Cause Large Changes in 3,4-Methylenedioxymethamphetamine (MDMA)-Induced Serotonin Neurotoxicity and Core Body Temperature in the Rat
Authors: Malberg Jessica E. , Seiden Lewis S.
Published: April 2018

The amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA) is a drug of abuse and has been shown to be neurotoxic to 5-HT terminals in many species. MDMA-engendered neurotoxicity has been shown to be affected by both ambient temperature and core body temperature. We now report that small (2°C) changes in ambient temperature produce changes in core temperature in MDMA-treated rats, but the same changes in ambient temperature do not affect core temperature of saline-treated animals. Furthermore, increases in core temperature of MDMA-treated animals increase neurotoxicity. Rats were given MDMA (20 or 40 mg/kg) or saline and placed in an ambient temperature of 20, 22, 24, 26, 28, or 30°C using a novel temperature measurement apparatus that controls ambient temperature ±0.5°C. Two weeks after MDMA treatment, the rats were killed, and regional 5-HT and 5-hydroxyindole acetic acid levels were analyzed as a measure of neurotoxicity. Rats treated with MDMA at 20 and 22°C showed a hypothermic core temperature response. Treatment with MDMA at 28 and 30°C produced a hyperthermic response. At ambient temperatures of 20–24°C, neurotoxicity was not observed in the frontal cortex, somatosensory cortex, hippocampus, or striatum. At ambient temperatures of 26–30°C, neurotoxicity was seen and correlated with core temperature in all regions examined. These data indicate that ambient temperature has a significant affect on MDMA neurotoxicity, core temperature, and thermoregulation in rats. This finding has implications on both the temperature dependence of the mechanism of MDMA neurotoxicity and human use because fatal hyperthermia is associated with MDMA use in humans.
The Activity of a Highly Promiscuous AP-1 Element Can Be Confined to Neurons by a Tissue-Selective Repressive Element
Authors: Weber Joseph R. M. , Skene J. H. Pate
Published: April 2018

Tissue-specific gene transcription can be determined by the use of either positive-acting or negative-acting DNA regulatory elements. We have analyzed a promoter from the growth-associated protein 43 (GAP-43) gene and found that it uses both of these mechanisms to achieve its high degree of neuron-specific activity. Two novel transcription factor binding sites, designated Cx1 and Cx2, drive promoter activity in neurons from developing cerebral cortex but not in several other cell types. The promoter also contains an activator protein 1 (AP-1) site that contributes to activity in neurons. The AP-1 site can drive promoter activity in a wide range of non-neuronal cells that express little or no endogenous GAP-43, but only in the absence of a tissue-specific repressive element located downstream of the GAP-43 TATA box. These findings suggest that the GAP-43 repressive element plays an important role in allowing AP-1 signaling pathways to modulate activity of the GAP-43 gene in neurons, without also causing inappropriate activation by AP-1 transcription factors in other cell types.
Type 1 Inositol 1,4,5-Trisphosphate Receptor Is Required for Induction of Long-Term Depression in Cerebellar Purkinje Neurons
Authors: Inoue Takafumi , Kato Kunio , Kohda Kazuhisa , Mikoshiba Katsuhiko
Published: April 2018

The inositol 1,4,5-trisphosphate receptor (InsP3R) is an intracellular Ca2+channel that releases Ca2+from internal Ca2+stores in response to InsP3. Although InsP3R is highly expressed in various regions of the mammalian brain, the functional role of this receptor has not been clarified. We show here that cerebellar slices prepared from mice with a disrupted InsP3R type 1 gene, which is predominantly expressed in Purkinje cells, completely lack long-term depression (LTD), a model of synaptic plasticity in the cerebellum. Moreover, a specific antibody against InsP3R1, introduced into wild-type Purkinje cells through patch pipettes, blocked the induction of LTD. These data indicate that, in addition to Ca2+influx through Ca2+channels on the plasma membrane, Ca2+release from InsP3R plays an essential role in the induction of LTD, suggesting a physiological importance for InsP3R in Purkinje cells.
Blocking N-Cadherin Function Disrupts the Epithelial Structure of Differentiating Neural Tissue in the Embryonic Chicken Brain
Authors: Gänzler-Odenthal Susanne I. I. , Redies Christoph
Published: April 2018

The cell adhesion molecule N-cadherin is ubiquitously expressed in the early neuroepithelium, with strongest expression in the ependymal lining. We blocked the function of N-cadherin during early chicken brain development by injecting antibodies against N-cadherin into the tectal ventricle of embryos at 4–5 d of incubation [embryonic day 4 (E4)–E5]. N-cadherin blockage results in massive morphological changes in restricted brain regions. At approximately E6, these changes consist of invaginations of pieces of the ependymal lining and the formation of neuroepithelial rosettes. The rosettes are composed of central fragments of ependymal lining, surrounded by an inner ventricular layer and an outer mantle layer. Radial glia processes are radially arranged around the ependymal centers of the rosettes. The normal layering of the neural tissue is thus preserved, but its coherent epithelial structure is disrupted. The observed morphological changes are restricted to specific brain regions such as the tectum and the dorsal thalamus, whereas the ventral thalamus and the pretectum are almost undisturbed. At E10–E11, analysis of late effects of N-cadherin blockage reveals that in the dorsal thalamus, gray matter is fragmented and disorganized; in the tectum, additional layers have formed at the ventricular surface. Together, these results indicate that N-cadherin function is required for the maintenance of a coherent sheet of neuroepithelium in specific brain regions. Disruption of this sheet results in an abnormal morphogenesis of brain gray matter.
Corticolimbic Dopamine Neurotransmission Is Temporally Dissociated from the Cognitive and Locomotor Effects of Phencyclidine
Authors: Adams Barbara , Moghaddam Bita
Published: April 2018

The behavioral syndrome produced by phencyclidine (PCP) and its analog ketamine represents a pharmacological model for some aspects of schizophrenia. Despite the multifaceted properties of these drugs, the main mechanism for their psychotomimetic and cognitive-impairing effects has been thought heretofore to involve the corticolimbic dopamine system. The present study examined the temporal relationship between alterations in corticolimbic dopamine and glutamate neurotransmission and two dopamine-dependent behavioral effects of PCP in the rodent that have relevance to the clinical phenomenology, namely, impairment of working memory, which is used to model the frontal lobe deficits associated with schizophrenia, and hyperlocomotion, which is used as a predictor of the propensity of a drug to elicit or exacerbate psychosis. PCP increased dopamine and glutamate efflux in the prefrontal cortex and nucleus accumbens, as measured by microdialysis. The increase in dopamine in both regions remained elevated well above baseline 2.5 hr after the injection, at which time the experiment was terminated. However, locomotor activity returned to baseline in <2 hr after injection. Furthermore, impaired performance in a discrete trial delayed alternation task, a rodent working memory task, was only evident up to 60 min after PCP injection; animals tested 80 min after injection, when cortical dopamine release was elevated at 300% of baseline, did not exhibit impaired performance. These findings indicate that activation of dopamine neurotransmission is not sufficient to sustain PCP-induced locomotion and impairment of working memory. Thus, effects of PCP, including a glutamatergic hyperstimulation, may be necessary to account for the psychotomimetic and cognitive-impairing effects of this drug.
Functionally Distinct Groups of Interneurons Identified During Rhythmic Carbachol Oscillations in HippocampusIn Vitro
Authors: McMahon Lori L. , Williams John H. , Kauer Julie A.
Published: April 2018

During distinct behavioral states, the hippocampus exhibits characteristic rhythmic electrical activity. Evidencein vivosuggests that both principal pyramidal cells and GABAergic interneurons participate in generating oscillations. We found that during rhythmic oscillations in area CA3, functionally distinct classes of interneurons could be identified, although all recorded interneurons had similar dendritic and axonal arbors. One group of interneurons was powerfully excited by CA3 pyramidal cells, whereas two other interneuron groups were relatively unaffected by pyramidal cell firing. One of these groups of interneurons was potently inhibited by other local interneurons during the pyramidal cell bursts. Our findings emphasize that morphologically similar cells are wired together very differently within the local circuit. The classes of hippocampal interneurons we have tentatively defined may be used during distinct behavioral states to switch the local network from one oscillatory state to another.
Expression of Kv1.1, a Shaker-Like Potassium Channel, Is Temporally Regulated in Embryonic Neurons and Glia
Authors: Hallows Janice L. , Tempel Bruce L.
Published: April 2018

Kv1.1, a Shaker-like voltage-gated potassium channel, is strongly expressed in a variety of neurons in adult rodents, in which it appears to be involved in regulating neuronal excitability. Here we show that Kv1.1 is also expressed during embryonic development in the mouse, exhibiting two transient peaks of expression around embryonic day 9.5 (E9.5) and E14.5. Using bothin situhybridization and immunocytochemistry, we have identified several cell types and tissues that express Kv1.1 RNA and protein. At E9.5, Kv1.1 RNA and protein are detected transiently in non-neuronal cells in several regions of the early CNS, including rhombomeres 3 and 5 and ventricular zones in the mesencephalon and diencephalon. At E14.5, several cell types in both the CNS and peripheral nervous system express Kv1.1, including neuronal cells (sensory ganglia and outer aspect of cerebral hemispheres) and glial cells (radial glia, satellite cells, and Schwann cell precursors). These data show that Kv1.1 is expressed transiently in a variety of neuronal and non-neuronal cells during restricted periods of embryonic development. Although the functional roles of Kv1.1 in development are not understood, the cell-specific localization and timing of expression suggest this channel may play a role in several developmental processes, including proliferation, migration, or cell–cell adhesion.
Immune Surveillance in the Injured Nervous System: T-Lymphocytes Invade the Axotomized Mouse Facial Motor Nucleus and Aggregate around Sites of Neuronal Degeneration
Authors: Raivich Gennadij , Jones Leonard L. , Kloss Christian U. A. , Werner Alexander , Neumann Harald , Kreutzberg Georg W.
Published: April 2018

Although the CNS is an established immune-privileged site, it is under surveillance by the immune system, particularly under pathological conditions. In the current study we examined the lymphocyte infiltration, a key component of this neuroimmune surveillance, into the axotomized facial motor nucleus and analyzed the changes in proinflammatory cytokines and the blood–brain barrier.

Peripheral nerve transection led to a rapid influx of CD3-, CD11a (αL, LFA1α)- and CD44-immunoreactive T-cells into the axotomized mouse facial motor nucleus, with a first, low-level plateau 2–4 d after injury, and a second, much stronger increase at 14 d. These T-cells frequently formed aggregates and exhibited typical cleaved lymphocyte nuclei at the EM level. Immunohistochemical colocalization with thrombospondin (TSP), a marker for phagocytotic microglia, revealed aggregation of the T-cells around microglia removing neuronal debris. The massive influx of lymphocytes at day 14 was also accompanied by the synthesis of mRNA encoding IL1β, TNFα, and IFN-γ. There was no infiltration by the neutrophil granulocytes, and the intravenous injection of horseradish peroxidase also showed an intact blood–brain barrier. However, mice withsevere combined immunodeficiency(SCID), which lack differentiated T- and B-cells, still exhibited infiltration with CD11a-positive cells. These CD11a-positive cells also aggregated around phagocytotic microglial nodules.

In summary, there is a site-selective infiltration of activated T-cells into the mouse CNS during the retrograde reaction to axotomy. The striking aggregation of these lymphocytes around neuronal debris and phagocytotic microglia suggests an important role for the immune surveillance during neuronal cell death in the injured nervous system.
Presynaptic Function during Muscle Remodeling in Insect Metamorphosis
Authors: Consoulas Christos , Levine Richard B.
Published: April 2018

During metamorphosis the leg neuromuscular system of the mothManduca sextaundergoes an extensive remodeling as the larval muscles degenerate and are replaced by new muscles in the adult. The terminal processes of persistent leg motoneurons undergo severe regression followed by regrowth (Consoulas et al., 1996), accompanied, as shown here, by the loss and re-establishment of functional presynaptic specializations. Before and shortly after the degeneration of the larval muscle, immunoreactivity for the vesicular protein synaptotagmin was localized to the presynaptic varicosities of the motoneurons. Similarly localized were distinct sites of Ca2+-dependent uptake of the fluorescent dye FM1-43. During myoblast migration and accumulation about the re-expanding motor axons, synaptotagmin immunoreactivity was widely distributed in axons, and specific FM1-43 staining revealed vesicle exocytosis in distal axon branches. During myoblast proliferation and fusion, and myotube formation, synaptotagmin staining remained widely distributed in nerve branches, whereas FM1-43 staining was more localized to subdomains of these nerve branches. These initial presynaptic active sites were transient and were replaced by new sites in more distal nerve processes as the muscle anlage increased in size and additional myotubes formed. After myotube separation, synaptotagmin staining disappeared from primary branches but remained distributed within secondary and high-order nerve branches. FM1-43 staining was detected in high-order branches only. During muscle fiber striation, growth, and maturation, both FM1-43 staining and synaptotagmin immunoreactivity became localized to terminal varicosities. Thus, presynaptic function can persist after the loss of the target and occurs transiently in axon shafts before becoming restricted to terminal domains as the underlying muscle fibers mature.
The Role of Inertial Sensitivity in Motor Planning
Authors: Sabes Philip N. , Jordan Michael I. , Wolpert Daniel M.
Published: April 2018

To achieve a given motor task a single trajectory must be chosen from the infinite set of possibilities consistent with the task. To investigate such motor planning in a natural environment, we examined the kinematics of reaching movements made around a visual obstacle in three-dimensional space. Within each session, the start and end points of the movement were uniformly varied around the obstacle. However, the distribution of the near points, where the paths came closest to the obstacle, showed a strong anisotropy, clustering at the poles of a preferred axis through the center of the obstacle. The preferred axes for movements made with the left and right arms were mirror symmetric about the midsagittal plane, suggesting that the anisotropy stems from intrinsic properties of the arm rather than extrinsic visual factors. One account of these results is a sensitivity model of motor planning, in which the movement path is skewed so that when the hand passes closest to the obstacle, the arm is in a configuration that is least sensitive to perturbations that might cause collision. To test this idea, we measured the mobility ellipse of the arm. The mobility minor axis represents the direction in which the hand is most inertially stable to a force perturbation. In agreement with the sensitivity model, the mobility minor axis was not significantly different from the preferred near point axis. The results suggest that the sensitivity of the arm to perturbations, as determined by its inertial stability, is taken into account in the planning process.
The Mormyrid Electrosensory LobeIn Vitro: Physiology and Pharmacology of Cells and Circuits
Authors: Grant Kirsty , Sugawara Yoshiko , Gómez Leonel , Z. Han Victor , Bell Curtis C.
Published: April 2018

This paper is concerned with the electrosensory lobe (ELL) of mormyrid electric fish as examined inin vitroslices. Intracellular recordings from morphologically identified cells and field potential recordings were used to characterize the physiology and pharmacology of ELL cells. Most intracellular recordings were from the Purkinje-like interneurons that are known as medium ganglion cells and from the two types of efferent neurons, large ganglion and large fusiform cells. Stimulation of primary afferent fibers elicits both excitatory and inhibitory effects in these cells, with the excitatory effects being mediated by both the AMPA and NMDA types of glutamate receptors and the inhibitory effects being mediated by both GABAAand glycine receptors. Parallel-fiber stimulation evokes an EPSP–IPSP sequence, with the EPSPs being mediated by both AMPA and NMDA receptors and the IPSPs being mediated by GABAAreceptors only. The parallel fiber-evoked EPSPs and IPSPs show marked paired-pulse facilitation. A large and unusually broad spike is recorded inside medium ganglion cells, and field potential responses suggest that this spike is propagated into the apical dendrites. The results provide essential information for understanding how peripheral and central inputs are integrated in ELL.
Activity-Dependent pH Shifts and Periodic Recurrence of Spontaneous Interictal Spikes in a Model of Focal Epileptogenesis
Authors: de Curtis Marco , Manfridi Alfredo , Biella Gerardo
Published: April 2018

The mechanisms that control the periodicity of spontaneous epileptiform cortical potentials were investigated in thein vitroisolated guinea pig brain preparation. A brief intracortical application of bicuculline in the piriform cortex induced spontaneous interictal spikes (sISs) that recurred with high periodicity (8.5 ± 3.1 sec, mean ± SD). Intracellular recordings from principal neurons showed that the early phase of the inter-sISperiod is caused by a GABAb receptor-mediated inhibitory potential. The late component of the interspike period correlated to a slowly decaying depolarization abolished at membrane potentials positive to −32.1 ± 5.3 mV and was not associated with membrane conductance changes. Specific pharmacological tests excluded the contribution of synaptic and intrinsic conductances to the late inter-sISinterval. Recordings with ion-sensitive electrodes demonstrated thatsISs determined both a rapid increase in extracellular K+concentration (0.5–1 mm) and an extracellular alkalinization (0.05–0.08 pH units) that slowly decayed during the inter-sISperiod and returned to control values just before a subsequentsISwas generated. These observations were not congruous with the presence of a silent period, because both extracellular increase in K+and alkalinization are commonly associated with an increase in neuronal excitability. Extracellular alkalinization could be correlated to ansIS-induced intracellular acidification, a phenomenon that reduces cell coupling by impairing gap junction function. When intracellular acidification was transiently prevented by arterial perfusion with NH4Cl (10–20 mm), spontaneous ictal-like epileptiform discharges were induced. In addition, the gap junction blockers octanol (0.2–2 mm) and 18-α-glycyrrethinic acid (20 μm) applied either via the arterial system or locally in the cortex completely and reversibly abolished thesIS. The results reported here suggest that the massive cell discharge associated with ansISinduce a strong inhibition, possibly secondary to a pH-dependent uncoupling of gap junctions, that regulatessISperiodicity.
Regional and Cellular Patterns ofreelinmRNA Expression in the Forebrain of the Developing and Adult Mouse
Authors: Alcántara Soledad , Ruiz Mónica , D’Arcangelo Gabriella , Ezan Frederic , de Lecea Luis , Curran Tom , Sotelo Constantino , Soriano Eduardo
Published: April 2018

Thereelingene encodes an extracellular protein that is crucial for neuronal migration in laminated brain regions. To gain insights into the functions of Reelin, we performed high-resolutionin situhybridization analyses to determine the pattern ofreelinexpression in the developing forebrain of the mouse. We also performed double-labeling studies with several markers, including calcium-binding proteins, GAD65/67, and neuropeptides, to characterize the neuronal subsets that expressreelintranscripts.reelinexpression was detected at embryonic day 10 and later in the forebrain, with a distribution that is consistent with the prosomeric model of forebrain regionalization. In the diencephalon, expression was restricted to transverse and longitudinal domains that delineated boundaries between neuromeres. During embryogenesis,reelinwas detected in the cerebral cortex in Cajal-Retzius cells but not in the GABAergic neurons of layer I. At prenatal stages,reelinwas also expressed in the olfactory bulb, and striatum and in restricted nuclei in the ventral telencephalon, hypothalamus, thalamus, and pretectum. At postnatal stages,reelintranscripts gradually disappeared from Cajal-Retzius cells, at the same time as they appeared in subsets of GABAergic neurons distributed throughout neocortical and hippocampal layers. In other telencephalic and diencephalic regions,reelinexpression decreased steadily during the postnatal period. In the adult, there was prominent expression in the olfactory bulb and cerebral cortex, where it was restricted to subsets of GABAergic interneurons that co-expressed calbindin, calretinin, neuropeptide Y, and somatostatin. This complex pattern of cellular and regional expression is consistent with Reelin having multiple roles in brain development and adult brain function.
Presynaptic and Postsynaptic Actions and Modulation of Neuroendocrine Neurons by a New Hypothalamic Peptide, Hypocretin/Orexin
Authors: van den Pol Anthony N. , Gao Xiao-Bing , Obrietan Karl , Kilduff Thomas S. , Belousov Andrei B.
Published: April 2018

A new orexigenic peptide called hypocretin (orexin) has recently been described in neurons of the lateral hypothalamus and perifornical area. The medial and lateral hypothalamus have been loosely called satiety and feeding centers of the brain, respectively. Approximately one-third of all medial and lateral hypothalamic neurons tested, but not hippocampal neurons, show a striking nanomolar sensitivity to hypocretin. As studied with calcium digital imaging with fura-2, hypocretin raises cytoplasmic calcium via a mechanism based on G-protein enhancement of calcium influx through plasma membrane channels. The peptide has a potent effect at both presynaptic and postsynaptic receptors. Most synaptic activity in hypothalamic circuits is attributable to axonal release of GABA or glutamate. With whole-cell patch-clamp recording, we show that hypocretin, acting directly at axon terminals, can increase the release of each of these amino acid transmitters. Two hypocretin peptides, hypocretin-1 and hypocretin-2, are coded by a single gene; neurons that respond to one peptide also respond to the other. In addition to its effect on feeding, we find that this peptide also regulates the synaptic activity of physiologically identified neuroendocrine neurons studied in hypothalamic slices containing the arcuate nucleus, suggesting a second function of hypocretin in hormone regulation. The widespread distribution of hypocretin axons, coupled with the strong response to the peptide at both presynaptic and postsynaptic sites, suggests that the peptide probably modulates a variety of hypothalamic regulatory systems and could regulate the axonal input to these regions presynaptically.