bluuebunny/crossref_metadata_2025 huggingface dataset:
Circadian Regulation of cGMP-Gated Channels of Vertebrate Cone Photoreceptors: Role of cAMP and Ras
Authors: Ko Gladys Y.-P. , Ko Michael L. , Dryer Stuart E.
Published: February 2004

Circadian oscillators in chicken cone photoreceptors regulate the gating properties of cGMP-gated cationic channels (CNGCs) such that they have a higher apparent affinity for cGMP during the subjective night. Here we show that cAMP, acting through protein kinase A (PKA), Ras, and Erk, is part of the circadian output pathway controlling CNGCs. Endogenous and exogenous cAMP cause activation of Erk and Ras, which are more active at night in cones, and increase the apparent affinity of CNGCs for cGMP. The Ras farnesyl transferase inhibitor manumycin-A, and a dominant-negative form of Ras (RasN17) block the circadian rhythms in CNGC gating, as well as the effects of cAMP. A dominant-negative form of the MEK kinase B-Raf also blocks circadian and cAMP modulation of CNGCs. The circadian output pathway modulating CNGC channels is comprised in part of cAMP → PKA → Ras → B-Raf → MEK → Erk → → CNGCs. cAMP activation of Ras and Erk occur within minutes, whereas modulation of CNGCs requires >1 hr. However, cAMP protagonists do not alter rhythms incPer2mRNA, and their effects on CNGCs cannot be attributed to clock phase-shifting.
Novel Features of Cryptochrome-Mediated Photoreception in the Brain Circadian Clock ofDrosophila
Authors: Klarsfeld André , Malpel Sébastien , Michard-Vanhée Christine , Picot Marie , Chélot Elisabeth , Rouyer François
Published: February 2004

InDrosophila, light affects circadian behavioral rhythms via at least two distinct mechanisms. One of them relies on the visual phototransduction cascade. The other involves a presumptive photopigment, cryptochrome (cry), expressed in lateral brain neurons that control behavioral rhythms. We show here thatcryis expressed in most, if not all, larval and adult neuronal groups expressing the PERIOD (PER) protein, with the notable exception of larval dorsal neurons (DN2s) in which PER cycles in antiphase to all other known cells. Forcingcryexpression in the larval DN2s gave them a normal phase of PER cycling, indicating that their unique antiphase rhythm is related to their lack ofcryexpression. We were able to directly monitor CRY protein inDrosophilabrainsin situ. It appeared highly unstable in the light, whereas in the dark, it accumulated in both the nucleus and the cytoplasm, including some neuritic projections. We also show that dorsal PER-expressing brain neurons, the adult DN1s, are the only brain neurons to coexpress the CRY protein and the photoreceptor differentiation factor GLASS. Studies of various visual system mutants and their combination with thecrybmutation indicated that the adult DN1s contribute significantly to the light sensitivity of the clock controlling activity rhythms, and that this contribution depends on CRY. Moreover, all CRY-independent light inputs into this central behavioral clock were found to require the visual system. Finally, we show that the photoreceptive DN1 neurons do not behave as autonomous oscillators, because their PER oscillations in constant darkness rapidly damp out in the absence of pigment-dispersing-factor signaling from the ventral lateral neurons.
Postsynaptic Density Assembly Is Fundamentally Different from Presynaptic Active Zone Assembly
Authors: Bresler Tal , Shapira Mika , Boeckers Tobias , Dresbach Thomas , Futter Marie , Garner Craig C. , Rosenblum Kobi , Gundelfinger Eckart D. , Ziv Noam E.
Published: February 2004

The cellular mechanisms involved in the formation of the glutamatergic postsynaptic density (PSD) are mainly unknown. Previous studies have indicated that PSD assembly may occurin situby a gradual recruitment of postsynaptic molecules, whereas others have suggested that the PSD may be assembled from modular transport packets assembled elsewhere. Here we used cultured hippocampal neurons and live cell imaging to examine the process by which PSD molecules from different layers of the PSD are recruited to nascent postsynaptic sites. GFP-tagged NR1, the essential subunit of the NMDA receptor, and ProSAP1/Shank2 and ProSAP2/Shank3, scaffolding molecules thought to reside at deeper layers of the PSD, were recruited to new synaptic sites in gradual manner, with no obvious involvement of discernible discrete transport particles. The recruitment kinetics of these three PSD molecules were remarkably similar, which may indicate that PSD assembly rate is governed by a common upstream rate-limiting process. In contrast, the presynaptic active zone (AZ) molecule Bassoon was observed to be recruited to new presynaptic sites by means of a small number of mobile packets, in full agreement with previous studies. These findings indicate that the assembly processes of PSDs and AZs may be fundamentally different.
Dopamine Operates as a Subsecond Modulator of Food Seeking
Authors: Roitman Mitchell F. , Stuber Garret D. , Phillips Paul E. M. , Wightman R. Mark , Carelli Regina M.
Published: February 2004

The dopamine projection to the nucleus accumbens has been implicated in behaviors directed toward the acquisition and consumption of natural rewards. The neurochemical studies that established this link made time-averaged measurements over minutes, and so the precise temporal relationship between dopamine changes and these behaviors is not known. To resolve this, we sampled dopamine every 100 msec using fast-scan cyclic voltammetry at carbon-fiber microelectrodes in the nucleus accumbens of rats trained to press a lever for sucrose. Cues that signal the opportunity to respond for sucrose evoked dopamine release (67 ± 20 nm) with short latency (0.2 ± 0.1 sec onset). When the same cues were presented to rats naive to the cue-sucrose pairing, similar dopamine signals were not observed. Thus, cue-evoked increases in dopamine in trained rats reflected a learned association between the cues and sucrose availability. Lever presses for sucrose occurred at the peak of the dopamine surges. After lever presses, and while sucrose was delivered and consumed, no further increases in dopamine were detected. Rather, dopamine returned to baseline levels. Together, the results strongly implicate subsecond dopamine signaling in the nucleus accumbens as a real-time modulator of food-seeking behavior.
Relationship between Excitation and Inhibition Underlying Size Tuning and Contextual Response Modulation in the Cat Primary Visual Cortex
Authors: Ozeki Hirofumi , Sadakane Osamu , Akasaki Takafumi , Naito Tomoyuki , Shimegi Satoshi , Sato Hiromichi
Published: February 2004

In the primary visual cortex (V1), the single-neuron response to a grating stimulus placed in the classical receptive field (CRF) is suppressed by a similar stimulus presented in the CRF surround. To assess the input mechanism underlying the surround suppression, we tested the effects of iontophoretically administered GABAA-receptor antagonist, bicuculline methiodide (BMI), for the 46 V1 neurons in anesthetized cats. First, the stimulus-size tuning curves were studied, with or without BMI administration, for each neuron by changing the size of the grating patch. During the BMI administration, the shape of the normalized size tuning curve did not change considerably. Second, the dependency of surround suppression on the orientation of the surround grating was examined. In the control, the surround suppression showed the clear orientation tuning that peaked at an orientation the same as the optimal orientation of the CRF response. The BMI administration did not change the orientation dependency of surround suppression. We also estimated the relative contribution of excitation and inhibition to the size and orientation tuning of surround suppression. It was concluded that cortical excitation and inhibition were well balanced, having similar tuning profiles for both stimulus size and orientation of the surround grating. Furthermore, surround stimuli used for V1 neurons suppressed the CRF response of neurons in the lateral geniculate nucleus. These results suggest that surround suppression is not primarily attributable to the intracortical inhibition, but because of a reduction of thalamocortical inputs, which drive the cortical excitation and inhibition, and a subsequent decrease in the cortical excitatory interactions.
Regionally Specific Distribution of Corticospinal Synapses Because of Activity-Dependent Synapse EliminationIn Vitro
Authors: Ohno Takae , Maeda Hitoshi , Sakurai Masaki
Published: February 2004

We have shown previously that the corticospinal tract (CST) with functional connections can be reconstructedin vitroin slice cocultures. Using that system, we stimulated the deep cortical layer and recorded field EPSPs (fEPSPs) along a 100 μm-interval lattice in the spinal gray matter. The specific, spatial synapse distribution on the dorsal side at 14 din vitro(DIV) basically corresponded to thein vivoarea in which CST axons terminate. Anterograde labeling of corticospinal axons with biocytin showed a similar terminal distribution on that side.In vitrodevelopment of synapse spatial distribution was investigated. fEPSPs were recorded all across the gray matter at 7 DIV, but amplitudes began to decrease on the ventral side at 9 DIV, dorsal-dominant distribution being nearly complete at 14 DIV. Anterograde labeling showed that the decrease in fEPSP amplitudes was associated with a decrease in the number of axon terminals on the ventral area. Decreases in the synaptic responses and terminals were blocked by applications ofd-2-amino-5-phosphonovaleric acid and tetrodotoxin, whereas 6-cyano-7-nitroquinoxaline-2,3-dione had a partial effect. These findings suggest that this regressive event, which occurs during development, is activity and NMDA dependent. Retrograde labeling with two colors of beads and an electrophysiological study that investigated the axon reflex showed that at 7 DIV most corticospinal neurons project to both the ventral and dorsal spinal cord, indicating that synapse decrease on the ventral side is attributable primarily to axon branch elimination rather than to death of cortical cells that send axons solely to that side.
Selective Ablation of a Class of Amacrine Cells Alters Spatial Processing in the Retina
Authors: Sinclair John R. , Jacobs Adam L. , Nirenberg Sheila
Published: February 2004

Several recent studies have suggested that the spatial tuning of retinal ganglion cells may be a more complex process than previously thought. The working hypothesis for many years was that the tuning was shaped by operations performed in the first synaptic layer of the retina, but recent work shows that operations in the second synaptic layer, involving amacrine cells, also play a significant role (Cook and McReynolds, 1998; Taylor, 1999; Flores-Herr et al., 2001). Although it is clear that amacrine cells are involved, the precise roles of the different amacrine subtypes in the many aspects of spatial tuning have not yet been established. Here we used a cell class ablation method to remove one subtype, the neuropeptide Y-expressing cells (NPY cells), and tapped into a part of the circuitry that tunes ganglion cells toward large spatial patterns (low spatial frequencies). When the subtype was ablated, ganglion cells tuned toward low spatial frequencies, both ON- and OFF-type cells, lost this preferential tuning. The effect was specific because ablation of another amacrine subtype did not produce it. Further analysis showed that the change in tuning was attributable to a decrease in the receptive field surround size of the ganglion cell. Other parameters, such as the size, strength, and asymmetry of the center and the strength of the surround, were not statistically significantly affected. These results thus show a mechanism for tuning cells to low spatial frequencies; an operation in the second synaptic layer, mediated by NPY cells, extends the surround of the ganglion cell.
Enteric Dopaminergic Neurons: Definition, Developmental Lineage, and Effects of Extrinsic Denervation
Authors: Li Z. S. , Pham T. D. , Tamir H. , Chen J. J. , Gershon M. D.
Published: February 2004

The existence of enteric dopaminergic neurons has been suspected; however, the innervation of the gut by sympathetic nerves, in which dopamine (DA) is the norepinephrine precursor, complicates analyses of enteric DA. We now report that transcripts encoding tyrosine hydroxylase (TH) and the DA transporter (DAT) are present in the murine bowel (small intestine > stomach or colon; proximal colon > distal colon). Because sympathetic neurons are extrinsic, transcripts encoding TH and DAT in the bowel are probably derived from intrinsic neurons. TH protein was demonstrated immunocytochemically in neuronal perikarya (submucosal >> myenteric plexus; small intestine > stomach or colon). TH, DA, and DAT immunoreactivities were coincident in subsets of neurons (submucosal > myenteric) in guinea pig and mouse intestinesin situand in cultured guinea pig enteric ganglia. Surgical ablation of sympathetic nerves by extrinsic denervation of loops of the bowel did not affect DAT immunoreactivity but actually increased numbers of TH-immunoreactive neurons, expression of mRNA encoding TH and DAT, and enteric DOPAC (the specific dopamine metabolite). The fetal gut contains transiently catecholaminergic (TC) cells. TC cells are the proliferating crest-derived precursors of mature neurons that are not catecholaminergic and, thus, disappear after embryonic day (E) 14 (mouse) or E15 (rat). TC cells appear early in ontogeny, and their development/survival is dependent onmash-1gene expression. In contrast, the intrinsic TH-expressing neurons of the murine bowel appear late (perinatally) and aremash-1independent. We conclude that the enteric nervous system contains intrinsic dopaminergic neurons that arise from amash-1-independent lineage of noncatecholaminergic precursors.
Enhancement of Working Memory in Aged Monkeys by a Sensitizing Regimen of Dopamine D1Receptor Stimulation
Authors: Castner Stacy A. , Goldman-Rakic Patricia S.
Published: February 2004

A natural consequence of aging is a loss of dopamine function and associated deficits in working memory in both human and nonhuman primates. Specifically, deficiency of D1receptor signaling has been implicated in age-related cognitive decline. Here, we report that an intermittent, sensitizing regimen of the D1dopamine agonist ABT-431 dramatically enhances working memory performance in aged rhesus monkeys, while either producing impairment or having little effect on performance in young adult monkeys. Importantly, cognitive enhancement in the aged monkeys was still evident for >1 year after cessation of D1treatment. Because intermittent exposure to low doses of amphetamine and other stimulants has been shown to enhance responsiveness to subsequent stimulant exposure, our findings suggest that sensitization of D1signaling may provide a novel neurobiological mechanism for improving a core cognitive process in conditions in which dopamine function has deteriorated, such as in normal aging and Parkinson's disease.
Diversity of Functional Astroglial Properties in the Respiratory Network
Authors: Graß Dennis , Pawlowski Petra G. , Hirrlinger Johannes , Papadopoulos Nestoras , Richter Diethelm W. , Kirchhoff Frank , Hülsmann Swen
Published: February 2004

A population of neurons in the caudal medulla generates the rhythmic activity underlying breathing movements. Although this neuronal network has attracted great attention for studying neuronal aspects of synaptic transmission, functions of glial cells supporting this neuronal activity remain unclear. To investigate the role of astrocytes in the respiratory network, we applied electrophysiological and immunohistochemical techniques to characterize astrocytes in regions involved in the generation and transmission of rhythmic activity. In the ventral respiratory group and the hypoglossal nucleus (XII) of acutely isolated brainstem slices, we analyzed fluorescently labeled astrocytes obtained from TgN(GFAP-EGFP) transgenic mice with the whole-cell voltage-clamp technique. Three subpopulations of astrocytes could be discerned by their distinct membrane current profiles. A first group of astrocytes was characterized by nonrectifying, symmetrical and voltage-independent potassium currents and a robust glutamate transporter response tod-aspartate. A second group of astrocytes showed additional A-type potassium currents, whereas a third group, identified by immunolabeling for the glial progenitor marker NG2, expressed outwardly rectifying potassium currents, smaller potassium inward currents, and only minimald-aspartate-induced transporter currents. Astrocytes of all groups showed kainate-induced inward currents.

We conclude that most of the astrocytes serve as a buffer system of excess extracellular glutamate and potassium; however, a distinct cell population (NG2-positive, A-type potassium currents) may play an important role for network plasticity.
ORP150/HSP12A Regulates Purkinje Cell Survival: A Role for Endoplasmic Reticulum Stress in Cerebellar Development
Authors: Kitao Yasuko , Hashimoto Kouichi , Matsuyama Tomohiro , Iso Hiroyuki , Tamatani Takeshi , Hori Osamu , Stern David M. , Kano Masanobu , Ozawa Kentaro , Ogawa Satoshi
Published: February 2004

The endoplasmic reticulum (ER) stress response contributes to neuronal survival in ischemia and neurodegenerative processes. ORP150 (oxygen-regulated protein 150)/HSP12A (heat shock protein 12A), a novel stress protein located in the ER, was markedly induced in Purkinje cells maximally at 4-8 d after birth, a developmental period corresponding to their vulnerability to cell death. Both terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end-labeling analysis and immunostaining using anti-activated caspase-3 antibody revealed that transgenic mice with targeted neuronal overexpression of ORP150 (Tg ORP150) displayed diminished cell death in the Purkinje cell layer and increased numbers of Purkinje cells up to 40 d after birth (p< 0.01), compared with those observed in heterozygous ORP150/HSP12A-deficient (ORP150+/-) mice and wild-type littermates (ORP150+/+). Cultured Purkinje cells from Tg ORP150 mice displayed resistance to both hypoxia- and AMPA-induced stress. Behavioral analysis, using rotor rod tasks, indicated impairment of cerebellar function in Tg ORP150 animals, consistent with the concept that enhanced survival of Purkinje cells results in dysfunction. These data suggest that ER chaperones have a pivotal role in Purkinje cell survival and death and thus may highlight the importance of ER stress in neuronal development.
Ectopic Expression of the Catalytic Subunit of Telomerase Protects against Brain Injury Resulting from Ischemia and NMDA-Induced Neurotoxicity
Authors: Kang Hyo Jung , Choi Yoon Sik , Hong Seung-Beom , Kim Kee-Won , Woo Ran-Sook , Won Seok Joon , Kim Eun Ju , Jeon Hee Kyung , Jo So-Young , Kim Tae Kook , Bachoo Robert , Reynolds Ian J. , Gwag Byoung Joo , Lee Han-Woong
Published: February 2004

The catalytic subunit of telomerase reverse transcriptase (TERT) protects dividing cells from replicative senescencein vitro. Here, we show that expression of TERT mRNA is induced in the ipsilateral cortical neurons after occlusion of the middle cerebral artery in adult mice. Transgenic mice that overexpress TERT showed significant resistance to ischemic brain injury. Among excitotoxicity, oxidative stress, and apoptosis comprising of routes of ischemic neuronal death, NMDA receptor-mediated excitotoxicity was reduced in forebrain cell cultures overexpressing TERT. NMDA-induced accumulation of cytosolic free Ca2+([Ca2+]c) was reduced in forebrain neurons from TERT transgenic mice, which was attributable to the rapid flow of [Ca2+]cinto the mitochondria from the cytosol without change in Ca2+influx and efflux through the plasma membrane. The present study provides evidence that TERT is inducible in postmitotic neurons after ischemic brain injury and prevents NMDA neurotoxicity through shift of the cytosolic free Ca2+into the mitochondria, and thus plays a protective role in ameliorating ischemic neuronal cell death.
Activation of Phasic Pontine-Wave Generator Prevents Rapid Eye Movement Sleep Deprivation-Induced Learning Impairment in the Rat: A Mechanism for Sleep-Dependent Plasticity
Authors: Datta Subimal , Mavanji Vijayakumar , Ulloor Jagadish , Patterson Elissa H.
Published: February 2004

Animal and human studies of sleep and learning have demonstrated that training on various tasks increases subsequent rapid eye movement (REM) sleep and phasic pontine-wave (P-wave) activity, followed by improvement in performance on the learned task. It is well documented that REM sleep deprivation after learning trials blocks the expected improvement in performance on subsequent retesting. Our aim was to test whether experimentally induced P-wave generator activation could eliminate the learning impairment produced by post-training REM sleep deprivation. Rats were trained on a two-way active avoidance-learning task. Immediately thereafter, two groups of those rats received a control vehicle (100 nl saline) microinjection and one group received a carbachol (50 ng in 100 nl saline) microinjection into the P-wave generator. The carbachol-injected group and one of the two control saline microinjected groups were selectively deprived of REM sleep during a 6 hr polygraphic recording session. All rats were then tested on the avoidance-learning task. The rats that received both the control saline injection and REM sleep deprivation showed learning deficits compared with the control saline-injected rats that were allowed to sleep normally. In contrast, the rats that received the carbachol microinjection and REM sleep deprivation demonstrated normal learning. These results demonstrate, for the first time, that carbachol-induced activation of the P-wave generator prevents the memory-impairing effects of post-training REM sleep deprivation. This evidence supports our hypothesis that the activation of the P-wave generator during REM sleep deprivation enhances a physiological process of memory, which occurs naturally during post-training REM sleep.
A Gephyrin-Related Mechanism Restraining Glycine Receptor Anchoring at GABAergic Synapses
Authors: Meier Jochen , Grantyn Rosemarie
Published: February 2004

Spinal cord neurons release glycine and GABA and accumulate glycine receptors (GlyRs) and GABAAreceptors in the same postsynaptic densities. In contrast, supramedullar neurons prefer GABA as a neurotransmitter and exclude GlyRs from postsynaptic anchoring. The general aim of the present study was to elucidate the mechanisms underlying transmitter-appropriate receptor accumulation at inhibitory synapses. Specifically, we intended to clarify the molecular basis for the prohibition of GlyR accumulation in the postsynaptic densities of GABAergic synapses. A green fluorescent protein (GFP)-tagged gephyrin-binding loop of the GlyR β subunit (GFP::βL) was used as a surrogate for full-length receptors to characterize the GlyR binding capacity of postsynaptic gephyrins in transfected neurons. Both in spinal cord neurons (SCNs) and hippocampal neurons (HNs) GFP::βL distribution displayed transmitter specificity; i.e., postsynaptic accumulation of GFP::βL was high opposite terminals able to release glycine and low opposite purely GABAergic terminals. When comparing SCN and HN cultures we found that the level of mRNA coding for gephyrin splice variants containing the cassette C5 (C5-gephyrins) was significantly higher in HNs. In HNs depleted of C5-gephyrins, both GFP::βL and endogenous GlyRs accumulated at postsynaptic GABAergic sites. Accordingly in SCNs, GFP-tagged C5-gephyrin displayed a preferential postsynaptic accumulation opposite GABAergic synapses. Comparison of glycinergic, mixed, and GABAergic synapses in SCNs showed that the degree of GlyR accumulation was inversely related to the amount of postsynaptic C5-gephyrin. These results identify the C5 splice variant of gephyrin as a factor regulating the transmitter-appropriate degree of GlyR accumulation at inhibitory synapses.
A1 Adenosine Receptor Upregulation and Activation Attenuates Neuroinflammation and Demyelination in a Model of Multiple Sclerosis
Authors: Tsutsui Shigeki , Schnermann Jurgen , Noorbakhsh Farshid , Henry Scot , Yong V. Wee , Winston Brent W. , Warren Kenneth , Power Christopher
Published: February 2004

The neuromodulator adenosine regulates immune activation and neuronal survival through specific G-protein-coupled receptors expressed on macrophages and neurons, including the A1 adenosine receptor (A1AR). Here we show that A1AR null (A1AR-/-) mice developed a severe progressive-relapsing form of experimental allergic encephalomyelitis (EAE) compared with their wild-type (A1AR+/+) littermates. Worsened demyelination, axonal injury, and enhanced activation of microglia/macrophages were observed in A1AR-/-animals. In addition, spinal cords from A1AR-/-mice demonstrated increased proinflammatory gene expression during EAE, whereas anti-inflammatory genes were suppressed compared with A1AR+/+animals. Macrophages from A1AR-/-animals exhibited increased expression of the proinflammatory genes, interleukin-1β, and matrix metalloproteinase-12 on immune activation when matched with A1AR+/+control cells. A1AR-/-macrophage-derived soluble factors caused significant oligodendrocyte cytotoxicity compared with wild-type controls. The A1AR was downregulated in microglia in A1AR+/+mice during EAE accompanied by neuroinflammation, which recapitulated findings in multiple sclerosis (MS) patients. Caffeine treatment augmented A1AR expression on microglia, with ensuing reduction of EAE severity, which was further enhanced by concomitant treatment with the A1AR agonist, adenosine amine congener. Thus, modulation of neuroinflammation by the A1AR represents a novel mechanism that provides new therapeutic opportunities for MS and other demyelinating diseases.
Optical Mapping of the Functional Organization of the Rat Trigeminal Nucleus: Initial Expression and Spatiotemporal Dynamics of Sensory Information Transfer during Embryogenesis
Authors: Momose-Sato Yoko , Honda Yoshiko , Sasaki Hiroshi , Sato Katsushige
Published: February 2004

We examined the functional organization of the rat trigeminal nuclear complex and its developmental dynamics using a multiple-site optical recording technique. Brainstem preparations were dissected from embryonic day 12 (E12)-E16 rat embryos, and stimulation was applied individually to the three branches of the trigeminal nerve (V1-V3). The action potential activity of presynaptic fibers was detected from E13, and the glutamate-mediated postsynaptic response was significantly observed from E15 on. At E14, the evoked signals usually consisted of only the action potential-related fast component. However, when extracellular Mg2+was removed, a significantdl-2-amino-5-phosphonovaleric acid-sensitive slow component appeared. These results suggest that postsynaptic function mediated by NMDA receptors is latently generated as early as E14. The response area of the three branches of the trigeminal nerve showed some functional somatotopic organization, with the ophthalmic (V1) nerve area medially located and the mandibular (V3) nerve area laterally located. The center of the trigeminal nuclear complex in which the activity of neurons and synaptic function was greatest shifted caudally with development, suggesting that the functional architecture of the trigeminal nuclear complex is not fixed but changes dynamically during embryogenesis. By electron microscopy, we could not observe clear correlations between functional data and morphological information; when we surveyed E16 preparations, we could not identify typical synaptic structures between the 1,1′-dioctyldecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate-labeled trigeminal nerve terminals and the neurons in the trigeminal nuclear complex. This implies that postsynaptic function in the trigeminal nuclear complex is generated before the appearance of the morphological structure of conventional synapses.
The Basolateral Amygdala Interacts with the Medial Prefrontal Cortex in Regulating Glucocorticoid Effects on Working Memory Impairment
Authors: Roozendaal Benno , McReynolds Jayme R. , McGaugh James L.
Published: February 2004

Previous findings indicate that the basolateral complex of the amygdala (BLA) interacts with other brain regions in regulating stress hormone effects on memory functions. Lesions of the BLA or infusions of a β-adrenoceptor antagonist into the BLA block glucocorticoid effects on both memory consolidation and retrieval when administered either systemically or directly into the hippocampus. The present experiments examined BLA and β-adrenoceptor involvement in regulating glucocorticoid effects on spatial working memory, a task that depends on the medial prefrontal cortex (mPFC). Male Sprague Dawley rats with bilateral sham- or NMDA-induced lesions of the BLA received either corticosterone (1.0 or 3.0 mg/kg, i.p.) systemically or the specific glucocorticoid receptor agonist 11β,17β-dihydroxy-6,21-dimethyl-17α-pregna-4,6-trien-20yn-3-one (RU 28362; 3.0 or 10.0 ng in 0.5 μl) into the mPFC shortly before testing on a delayed alternation task in a T-maze. Both glucocorticoid treatments induced comparable impairments in working memory performance in sham-lesioned controls. Although lesions of the BLA alone did not affect working memory, BLA lesions blocked the impairment induced by either corticosterone or RU 28362. Likewise, systemic injections of the centrally acting β-adrenoceptor antagonist propranolol (2.0 mg/kg, i.p.) given before testing prevented corticosterone-induced working memory impairment. These findings indicate that BLA activity is essential for enabling glucocorticoid effects in the mPFC on working memory and suggest that stress hormone-induced modulation of working memory involves noradrenergic activation.
Multiple Roles for Slits in the Control of Cell Migration in the Rostral Migratory Stream
Authors: Nguyen-Ba-Charvet Kim T. , Picard-Riera Nathalie , Tessier-Lavigne Marc , Baron-Van Evercooren Anne , Sotelo Constantino , Chédotal Alain
Published: February 2004

The subventricular zone (SVZ) contains undifferentiated cells, which proliferate and generate olfactory bulb (OB) interneurons. Throughout life, these cells leave the SVZ and migrate along the rostral migratory stream (RMS) to the OB where they differentiate.In vitro, the septum and the choroid plexus (CP) secrete repulsive factors that could orient the migration of OB precursors. Slit1 and Slit2, two known chemorepellents for developing axons, can mimic this effect. We show here that the Slit receptors Robo2 and Robo3/Rig-1 are expressed in the SVZ and the RMS and that Slit1 and Slit2 are still present in the adult septum. UsingSlit1/2-deficient mice, we found that Slit1 and Slit2 are responsible for both the septum and the CP repulsive activityin vitro. In adult mice lacking Slit1, small chains of SVZ-derived cells migrate caudally into the corpus callosum, supporting a role for Slits in orienting the migration of SVZ cells. Surprisingly, in adult mice, Slit1 was also expressed by type A and type C cells in the SVZ and RMS, suggesting that Slit1 could act cell autonomously. This hypothesis was tested using cultures of SVZ explants or isolated neurospheres fromSlit1-/- orSlit1+/- mice. In both types of cultures, the migration of SVZ cells was altered in the absence of Slit1. This suggests that the regulation of the migration of OB precursors by Slit proteins is complex and not limited to repulsion.
Dysregulation in the Suicide Brain: mRNA Expression of Corticotropin-Releasing Hormone Receptors and GABAAReceptor Subunits in Frontal Cortical Brain Region
Authors: Merali Zul , Du Lisheng , Hrdina Pavel , Palkovits Miklos , Faludi Gabor , Poulter Michael O. , Anisman Hymie
Published: February 2004

Corticotropin-releasing hormone (CRH) and GABA have been implicated in depression, and there is reason to believe that GABA may influence CRH functioning. The levels of CRH, and mRNA for CRH-binding protein, CRH1, and CRH2receptors, as well as various GABAAreceptor subunits (α1, α2, α3, α4, α5, δ, and γ2), were determined in several frontal cortical brain regions of depressed suicide victims and nondepressed individuals who had not died by suicide. Relative to the comparison group, CRH levels were elevated in frontopolar and dorsomedial prefrontal cortex, but not in the ventrolateral prefrontal cortex of suicide victims. Conversely, using quantitative PCR analyses, it was observed that, in frontopolar cortex, mRNA for CRH1, but not CRH2, receptors were reduced in suicide brains, possibly secondary to the high levels of CRH activity. In addition, mRNA of the α1, α3, α4, and δ receptor subunits was reduced in the frontopolar region of suicide victims. Interestingly, a partial analysis of the GABAAreceptor functional genome revealed high cross-correlations between subunit expression in cortical regions of nondepressed individuals, suggesting a high degree of coordinated gene regulation. However, in suicide brains, this regulation was perturbed, independent of overall subunit abundance. These findings raise the possibility that the CRH and GABAAreceptor subunit changes, or the disturbed coordination between these GABAAreceptor subunits, contribute to depression and/or suicidality or are secondary to the illness/distress associated with it.
Exacerbation of Motor Neuron Disease by Chronic Stimulation of Innate Immunity in a Mouse Model of Amyotrophic Lateral Sclerosis
Authors: Nguyen Minh Dang , D'Aigle Thierry , Gowing Geneviève , Julien Jean-Pierre , Rivest Serge
Published: February 2004

Innate immunity is a specific and organized immunological program engaged by peripheral organs and the CNS to maintain homeostasis after stress and injury. In neurodegenerative disorders, its putative deregulation, featured by inflammation and activation of glial cells resulting from inherited mutations or viral/bacterial infections, likely contributes to neuronal death. However, it remains unclear to what extent environmental factors and innate immunity cooperate to modulate the interactions between the neuronal and non-neuronal elements in the perturbed CNS. In the present study, we addressed the effects of acute and chronic administration of lipopolysaccharide (LPS), a Gram-negative bacterial wall component, in a genetic model of neurodegeneration. Transgenic mice expressing a mutant form of the superoxide dismutase 1 (SOD1G37R) linked to familial amyotrophic lateral sclerosis were challenged intraperitoneally with a single nontoxic or repeated injections of LPS (1 mg/kg). At different ages, SOD1G37Rmice responded normally to acute endotoxemia. Remarkably, only a chronic challenge with LPS in presymptomatic 6-month-old SOD1G37Rmice exacerbated disease progression by 3 weeks and motor axon degeneration. Closely associated with the severity of disease is the stronger and restricted upregulation of the receptor of innate immunity Toll-like receptor 2 and proinflammatory cytokines in degenerating regions of the ventral spinal cord and efferent fiber tracts of the brain from the LPS-treated SOD1G37Rmice. This robust immune response was not accompanied by the establishment of acquired immunity. Our results provide solid evidence that environmental factors and innate immunity can cooperate to influence the course of disease of an inherited neuropathology.
Rapid Arrival and Integration of Ascending Sensory Information in Layer 1 Nonpyramidal Neurons and Tuft Dendrites of Layer 5 Pyramidal Neurons of the Neocortex
Authors: Zhu Yinghua , Zhu J. Julius
Published: February 2004

Ascending sensory inputs arriving in layer 1 of the neocortex carry crucial signals for detecting salient information; but how the inputs are processed in layer 1 is unknown. Using a whole-cellin vivorecording technique targeting nonpyramidal neurons in layer 1 and tuft dendrites of layer 5 pyramidal neurons in layers 1-2, we examined the processing of these ascending sensory inputs in the barrel cortex. Here, we show that local circuit and deeper-layer-projecting neurons in layer 1, as well as tuft dendrites and somata of layer 5 pyramidal neurons, respond to multiple whiskers (6-15) with robust EPSPs. Remarkably, the latency for primary whisker-evoked responses is as short as ∼5-7 msec in layer 1 neurons and tuft dendrites of layer 5 pyramidal neurons. In addition, the latency for primary whisker-evoked responses in tuft dendrites of layer 5 pyramidal neurons is ∼1 msec shorter than that in somata. These results indicate that ascending sensory inputs arrive in layers 1 and 4 concurrently, which provides a neural mechanism for rapid integration and coincident detection of salient sensory information.
A Role for Prefrontal Cortex in Memory Storage for Trace Fear Conditioning
Authors: Runyan Jason D. , Moore Anthony N. , Dash Pramod K.
Published: February 2004

The prefrontal cortex has been shown to participate in the association of events separated by time. However, it is not known whether the prefrontal cortex stores the memory for these relationships. Trace conditioning is a form of classical conditioning in which a time gap separates the conditioned stimulus (CS) from the unconditioned stimulus (US), the association of which has been shown to depend on prefrontal activity. Here we demonstrate that inhibition of extracellular signal-regulated kinase (Erk) cascade (a biochemical pathway involved in long-term memory storage) in the rat medial prefrontal cortex did not interfere with memory encoding for trace fear conditioning but impaired memory retention. In addition, animals displayed impaired memory for the irrelevancy of the training context. Hippocampal Erk phosphorylation was found to have a later time course than prefrontal Erk phosphorylation after trace fear conditioning, indicating a direct role for the prefrontal cortex in associative memory storage for temporally separated events as well as in memory storage of relevancy.
A Novel DNA Enzyme Reduces Glycosaminoglycan Chains in the Glial Scar and Allows Microtransplanted Dorsal Root Ganglia Axons to Regenerate beyond Lesions in the Spinal Cord
Authors: Grimpe Barbara , Silver Jerry
Published: February 2004

CNS lesions induce production of ECM molecules that inhibit axon regeneration. One major inhibitory family is the chondroitin sulfate proteoglycans (CSPGs). Reduction of their glycosaminoglycan (GAG) chains with chondroitinase ABC leads to increased axon regeneration that does not extend well past the lesion. Chondroitinase ABC, however, is unable to completely digest the GAG chains from the protein core, leaving an inhibitory “stub” carbohydrate behind. We used a newly designed DNA enzyme, which targets the mRNA of a critical enzyme that initiates glycosylation of the protein backbone of PGs, xylosyltransferase-1. DNA enzyme administration to TGF-β-stimulated astrocytes in culture reduced specific GAG chains. The same DNA enzyme applied to the injured spinal cord led to a strong reduction of the GAG chains in the lesion penumbra and allowed axons to regenerate around the core of the lesion. Our experiments demonstrate the critical role of PGs, and particularly those in the penumbra, in causing regeneration failure in the adult spinal cord.
Alteration in uterine contractility in mares with experimentally induced placentitis
Authors: McGlothlin J A , Lester G D , Hansen P J , Thomas M , Pablo L , Hawkins D L , LeBlanc M M
Published: February 2004

An experimental model of ascending placentitis was developed in the mare to characterize the uterine myoelectrical pattern in late gestation and determine how ascending placentitis altered this pattern. In experiment 1, myometrial electrical activity was analyzed during the early morning, late morning and evening hours in four mares in the last 15 days of gestation to identify patterns of activity. In experiment 2, nine mares received intra-cervical inoculations ofStreptococcus equisubspecieszooepidemicus. Myoelectrical activity in the early morning and evening hours in these mares was compared with four control mares. In experiment 1, the number of spike burst clusters >30 s was greater in the evening than in the late morning hours (P< 0.04). Spike burst activity (number × duration) of mares in experiment 1 was similar during day and night recordings until the last 6 days of gestation when it gradually increased each evening until parturition (P< 0.05). In experiment 2, control mares experienced a gradual increase in the number of small spike burst clusters in the last 6 days (P= 0.008) and an increase in large and small spike burst clusters in the evening hours in the last 4 days of gestation (P= 0.03). Mares with experimentally induced placentitis never exhibited a rise in spike burst clusters but had an increase in the mean duration and activity index of large spike burst clusters in the 4 days before parturition (P< 0.04). In conclusion, control mares had a progressive, reversible rise in myoelectrical activity at night in the week preceding parturition. This was not observed in mares with experimentally induced placentitis. They exhibited an increase in the intensity and duration of large spike burst clusters possibly in response to local inflammation.
Evidence that lamprey GnRH-III does not release FSH selectively in cattle
Authors: Amstalden M , Zieba D A , Garcia M R , Stanko R L , Welsh T H , Hansel W H , Williams G L
Published: February 2004

Experiments were performed to test the hypothesis that lamprey GnRH-III (lGnRH-III) selectively releases FSH. Primary cultures of bovine adenohypophyseal cells were treated with mammalian GnRH (mGnRH) and lGnRH-III (10−9, 10−8, 10−7 and 10−6 M) or control media in Experiment 1. All doses of mGnRH and the two highest doses of lGnRH-III stimulated (P < 0.001) a non-selective release of LH and FSH. In Experiments 2–4, Latin Square designs were utilized in vivo to examine whether physiological and hormonal milieu regulate putative selective effects of lGnRH-III. In Experiments 2 and 3, ovariectomized cows with basal levels of estradiol only (Experiment 2) or in combination with luteal phase levels of progester-one (Experiment 3) were injected with mGnRH and lGnRH-III (0.055, 0.11, 0.165 and 1.1 μg/kg body weight (BW) and saline. All doses of mGnRH released (P < 0.001) LH and FSH, but only the highest dose of lGnRH-III stimulated (P < 0.001) a non-selective release of both LH and FSH (Experiment 3). For Experiments 4A and 4B, intact, mid-luteal phase cows were injected with mGnRH and lGnRH-III (1.1 μg/kg BW; Experiment 4A), lGnRH-III (1.1 and 4.4 μg/kg BW; Experiment 4B) and saline. As before, mGnRH released (P < 0.001) both LH and FSH at all doses. In contrast, lGnRH-III at the highest dose released (P < 0.001) LH but not FSH. These findings suggest that lGnRH-III may act as a weak competitor for the mGnRH receptor and do not support the hypothesis that it selectively releases FSH in cattle.
The influence of maternal size on pre- and postnatal growth in the horse: III Postnatal growth
Authors: Allen W R , Wilsher Sandra , Tiplady Clare , Butterfield R M
Published: February 2004

The growth parameters exhibited by seven Thoroughbred (Tb) foals that had experienced a ‘restricted’in uteroexistence following transfer as embryos to the uteri of smaller Pony (P) mares (Tb-in-P) and, conversely, six P foals that experienced a ‘luxurious’in uteroexistence after transfer to larger Tb mares (P-in-Tb), were compared from birth to 3 years of age with those exhibited by six normal Tb-in-Tb and six P-in-P foals conceived by within-breed artificial insemination. Bodyweight, height at the withers, girth, poll-to-nose length, crown–rump length and three foreleg longbone measurements were made at regular intervals. At birth, an approximate 15% reduction or increase in parameters was observed in the Tb-in-P and P-in-Tb respectively, which declined to 5% by 3 years of age. Growth post partum was affected by restricted or enhanced growthin utero. In the first 6 months post partum, growth rate was enhanced in the previously restricted Tb-in-P foals and curbed in the previously enhanced P-in-Tb foals compared with their respective controls. Overall, the similarity of the responses of the offspring to both ‘restriction’ and ‘luxury’in uteroensured that no major changes to conformation resulted from either treatment. Thus, the Thoroughbreds carried by the Pony mares were merely scaled down versions of the Tb-in-Tb controls while the Ponies carried by the Thoroughbred mares were scaled up versions of the P-in-P controls.
Relationships between FSH patterns and follicular dynamics and the temporal associations among hormones in natural and GnRH-induced gonadotropin surges in heifers
Authors: Haughian J M , Ginther O J , Kot K , Wiltbank M C
Published: February 2004

Preovulatory LH and FSH surges and the subsequent periovulatory FSH surge were studied in heifers treated with a single injection of GnRH (100 μg, n = 6) or saline (n = 7). Blood samples were collected every hour from 6 h before treatment until 12 h after the largest follicle reached ≥8.5 mm (expected beginning of follicular deviation). The GnRH-induced preovulatory LH and FSH surges were higher at the peak and shorter in duration than in controls, but the area under the curve was not different between groups. The profiles of the preovulatory LH and FSH surges were similar within each treatment group, suggesting that the two surges involved a common GnRH-dependent mechanism. Concentrations of FSH in controls at the nadir before the preovulatory surge and at the beginning and end of the periovulatory surge were not significantly different among the three nadirs. A relationship between variability in the periovulatory FSH surge and number of 5.0 mm follicles was shown by lower FSH concentrations during 12–48 h after the beginning of the surge in heifers with more follicles (11.0 ± 1.0 follicles (mean±s.e.m.) n = 7) than in heifers with fewer follicles (5.7 ± 0.4, n = 6). This result was attributed to increased FSH suppression from increased numbers of follicles reaching 5.0 mm. Grouping of heifers into those with longer vs shorter intervals from a 4.5 mm to an 8.5 mm largest follicle did not disclose any relationship between length of the interval and FSH characteristics (e.g. profile of surge, area under curve, FSH concentrations at specific events). The hypothesis of a relationship between variation in the periovulatory FSH surge and variation in follicular dynamics was supported for the number of 5.0 mm follicles but not for the hour the largest follicle reached 8.5 mm. Thus, the expected time of follicle deviation was not altered by the extensive variation in the wave-stimulating FSH surge.
Ammonium exposure and pyruvate affect the amino acid metabolism of bovine blastocysts in vitro
Authors: Orsi Nicolas M , Leese Henry J
Published: February 2004

The accumulation of ammonium is a major artefact ofin vitroembryo culture. This study has examined ammonium production and potential mechanisms of disposal in preimplantation bovine blastocysts. Embryos were produced byin vitromaturation and fertilisation of oocytes, and cultured in synthetic oviduct fluid containing amino acids and BSA (SOFaaBSA). Ammonium/urea concentrations were determined enzymatically. Amino acid appearance/disappearance ‘profiles’ of single blastocysts were determined at 0, 1.25 and 2.5 mM NH4Cl (with or without 0.33 mM pyruvate), and with or without 10 mM dipicolinic acid (DPCA; a glutamate dehydrogenase (GLDH) inhibitor) or 2 mM amino-oxyacetate (AOA; a transaminase inhibitor). Free ammonium was produced at a rate of 4.281 (±0.362) pmol/embryo/h, while urea production was undetectable. The presence/absence of pyruvate affected amino acid profiles, especially alanine appearance (P< 0.001), glutamate disappearance (P< 0.05) and overall turnover (the sum of appearance and disappearance) (P< 0.001). GLDH inhibition with DPCA had no effect on amino acid overall disappearance, but glutamate disappearance increased, while that of arginine decreased (P< 0.05). The transaminase inhibitor, AOA, depressed turnover (P< 0.05), aspartate and glutamate disappearance, and alanine appearance. Thus, bovine blastocysts release ammonium as free ions or fix them, not as urea, but as alanine, possibly glutamine and, less likely, arginine. An active role for GLDH and transaminases in regulating blastocyst amino acid metabolism was demonstrated.