bluuebunny/crossref_metadata_2025_split huggingface dataset:
Group 1 and 2 Metabotropic Glutamate Receptors Play Differential Roles in Hippocampal Long-Term Depression and Long-Term Potentiation in Freely Moving Rats
Authors: Manahan-Vaughan Denise 
Published: April 2018

This study examined the role of metabotropic glutamate receptors (mGluRs) in hippocampal long-term depression (LTD)in vivo. The group 1 mGluR antagonist (S)4-carboxyphenylglycine (4CPG), group 1/2 antagonist (RS)-α-methyl-4-carboxyphenylglycine (MCPG), and group 2 antagonists (RS)-α-methylserine-O-phos-phate monophenyl ester (MSOPPE) and (2S)-α-ethylglutamic acid (EGLU) were used. The NMDA receptor antagonistd(−)-2-amino-5-phosphonopentanoic acid (AP5) was used to examine the NMDA receptor contribution to the observed LTD. Adult male Wistar rats underwent implantation of stimulating and recording electrodes into the Schaffer collaterals and CA1 stratum radiatum, respectively. After recovery of 5–7 d, the field EPSP was measured from freely moving animals. Drugs were applied either before or after 1 Hz low-frequency train (LFT) or 100 Hz stimulation via a cannula implanted in the lateral cerebral ventricle. Nine hundred pulses at 1 Hz produced an LTD that was marked and long-lasting. This LTD was completely inhibited by pre-LFT application of AP5. MCPG inhibited LTD from 2 hr post-LFT. 4CPG partially impaired LTD. MSOPPE and EGLU completely blocked induction of LTD, although short-term depression remained intact. MSOPPE did not block long-term potentiation (LTP) induced by 100 Hz stimulation, whereas 4CPG produced a significant inhibition. When MSOPPE was present, LTD could not be induced either before or after LTP induction, whereas LTD could be induced in an identical protocol in vehicle-injected animals.These results suggest a differential role for mGluRs in NMDA receptor-dependent hippocampal LTDin vivo. Group 1 mGluRs may play a role in both LTD and LTP, whereas group 2 mGluRs may be critically involved only in LTD induction.
Glycinergic Inhibition Contributes to the Generation of Rostral Scratch Motor Patterns in the Turtle Spinal Cord
Authors: Currie Scott N. , Lee Steven 
Published: April 2018

Cutaneous stimulation within the rostral scratch receptive field in a low spinal-immobilized turtle elicits a fictive rostral scratch reflex characterized by robust rhythmic motor output from ipsilateral hindlimb muscle nerves and weaker, alternating motor discharge in contralateral nerves. Simultaneous bilateral stimulation elicits bilateral rostral scratch motor patterns in which activity on the right and left sides alternates.We investigated the role of glycinergic inhibition in the generation and coordination of fictive rostral scratch motor patterns. Glycine (2 or 5 mm) and strychnine (5–50 μm), a glycine antagonist, were superfused over the anterior spinal hindlimb enlargement while fictive rostral scratch motor output was recorded bilaterally from hindlimb muscle nerves in the form of electroneurograms (ENGs). Although glycine reduced rostral scratch burst frequencies, strychnine tended to increase burst frequency. Strychnine also changed the shape of hip flexor ENG bursts, resulting in more abrupt burst onsets, indicating an earlier recruitment of motor neurons with large ENG spikes. During bilateral stimulation, strychnine increased the variability of interlimb phase values (left vs right hip flexor bursts) but did not abolish right-left alternation.These results indicate that glycinergic neurons in or near the anterior hindlimb enlargement contribute to the overall timing of the rostral scratch rhythm and to the recruitment timing of individual hip flexor motor neurons within each scratch burst. Our data also indicate that glycinergic mechanisms contribute to, but are not critically important for, maintaining an alternating interlimb coordination during bilateral scratch motor patterns.
Adenosine A1Receptor-Mediated Activation of Phospholipase C in Cultured Astrocytes Depends on the Level of Receptor Expression
Authors: Biber Knut , Klotz Karl-Norbert , Berger Mathias , Gebicke-Härter Peter J. , van Calker Dietrich 
Published: April 2018

Adenosine A1receptors induce an inhibition of adenylyl cyclase via G-proteins of the Gi/ofamily. In addition, simultaneous stimulation of A1receptors and of receptor-mediated activation of phospholipase C (PLC) results in a synergistic potentiation of PLC activity. Evidence has accumulated that Gβγ subunits mediate this potentiating effect. However, an A1receptor-mediated increase in extracellular glutamate was suggested to be responsible for the potentiating effect in mouse astrocyte cultures. We have investigated the synergistic activation of PLC by adenosine A1and α1adrenergic receptors in primary cultures of astrocytes derived from different regions of the newborn rat brain. It is reported here that (1) adenosine A1receptor mRNA as well as receptor protein is present in astrocytes from all brain regions, (2) A1receptor-mediated inhibition of adenylyl cyclase is of similar extent in all astrocyte cultures, (3) the A1receptor-mediated potentiation of PLC activity requires higher concentrations of agonist than adenylyl cyclase inhibition and is dependent on the expression level of A1receptor, and (4) the potentiating effect on PLC activity is unrelated to extracellular glutamate.Taken together, our data support the notion that βγ subunits are the relevant signal transducers for A1receptor-mediated PLC activation in rat astrocytes. Because of the lower affinity of βγ, as compared with α subunits, more βγ subunits are required for PLC activation. Therefore, only in cultures with higher levels of adenosine A1receptors is the release of βγ subunits via Gi/oactivation sufficient to stimulate PLC. It is concluded that variation of the expression level of adenosine A1receptors may be an important regulatory mechanism to control PLC activation via this receptor.
Stretch Hyperreflexia of Triceps Surae Muscles in the Conscious Cat after Dorsolateral Spinal Lesions
Authors: Taylor J. S. , Friedman R. F. , Munson J. B. , Vierck Jr C. J. 
Published: April 2018

Resistive force and electromyograms from triceps surae muscles were measured during dorsiflexion of both ankles of awake cats before and after interruption of one dorsolateral funiculus (DLF). DLF lesions produced ipsilateral increases in dynamic and static reflex force that persisted over 66 weeks. The increase in dynamic reflex force was velocity sensitive, as demonstrated by a greater effect for 60°/sec than for 10°/sec dorsiflexion. Also, the lesions increased dynamic force to a greater extent than static force (increased dynamic index). Background force (recorded immediately before each reflex response) was elevated ipsilaterally. However, increases in reflex force were observed when preoperative and postoperative background forces were matched within 10% and were associated with equivalent resting levels of electromyographic (EMG) activity. Resistive reflex force was significantly correlated with EMG responses to dorsiflexion and was not determined by nonreflexive mechanical stiffness of the muscles. Contralateral background and reflex force and associated EMG activity were decreased slightly, comparing preoperative and postoperative records.Clinical testing revealed ipsilateral postoperative increases in extensor tone, increased resistance to hindlimb flexion, hypermetria during positive support responses, and appearance of the Babinski reflex. However, the most reliable tests of DLF lesion effects were the quantitative measures of dynamic and static reflex amplitude. The enhancement of stretch reflexes is suggestive of spasticity. However, hyperactive stretch reflexes, hypertonicity, and the Babinski reflex were observed soon after interruption of the ipsilateral DLF, in contrast to a gradual development of positive signs that is characteristic of a more broadly defined spastic syndrome from large spinal lesions. Also, other signs that often are included in the spastic syndrome, including clonus, increased flexor reflex activity, and flexor spasms, did not result from DLF lesions. Thus, unilateral DLF lesions provide a model of spasticity but produce only several components of a more inclusive spastic syndrome.
Diverse Expression and Distribution ofShakerPotassium Channels during the Development of theDrosophilaNervous System
Authors: Rogero Oscar , Hämmerle Barbara , Tejedor Francisco J. 
Published: April 2018

The spatio-temporal expression ofShaker(Sh) potassium channels (Kch) in the developing and adult nervous system ofDrosophilahas been studied at the molecular and histological level using specific antisera.ShKch are distributed in most regions of the nervous system, but their expression is restricted to only certain populations of cells.ShKch have been found in the following three locations: in synaptic areas of neuropile, in axonal fiber tracks, and in a small number of neuronal cell bodies. This wide subcellular localization, together with a diverse distribution, implicatesShKch in multiple neuronal functions.Experiments performed withShmutants that specifically eliminate a few of theShKch splice variants clearly demonstrate an abundant differential expression and usage of the wide repertoire ofShisoforms, but they do not support the idea of extensive segregation of these isoforms among different populations of neurons.ShKch are predominantly expressed at late stages of postembryonic development and adulthood. Strikingly, wide changes in the repertoire ofShsplice isoforms occur some time after the architecture of the nervous system is complete, indicating that the expression ofShKch contributes to the final refinements of neuronal differentiation. These late changes in the expression and distribution ofShKch seem to correlate with activity patterns suggesting thatShKch may be involved in adaptative mechanisms of excitability.
GABAergic Neurons in Barrel Cortex Show Strong, Whisker-Dependent Metabolic Activation during Normal Behavior
Authors: McCasland James S. , Hibbard Lyndon S. 
Published: April 2018

Electrophysiological data from the rodent whisker/barrel cortex indicate that GABAergic, presumed inhibitory, neurons respond more vigorously to stimulation than glutamatergic, presumed excitatory, cells. However, these data represent very small neuronal samples in restrained, anesthetized, or narcotized animals or in cortical slices. Histochemical data from primate visual cortex, stained for the mitochondrial enzyme cytochrome oxidase (CO) and for GABA, show that GABAergic neurons are more highly reactive for CO than glutamatergic cells, indicating that inhibitory neurons are chronically more active than excitatory neurons but leaving doubt about the short-term stimulus dependence of this activation. Taken together, these results suggest that highly active inhibitory neurons powerfully influence relatively inactive excitatory cells but do not demonstrate directly the relative activities of excitatory and inhibitory neurons in the cortexduring normal behavior.We used a novel double-labeling technique to approach the issue of excitatory and inhibitory neuronal activation during behavior. Our technique combines high-resolution 2-deoxyglucose (2DG), immunohistochemical staining for neurotransmitter-specific antibodies, and automated image analysis to collect the data. We find that putative inhibitory neurons in barrel cortex of behaving animals are, on average, much more heavily 2DG-labeled than presumed excitatory cells, a pattern not seen in animals anesthetized at the time of 2DG injection. This metabolic activation is dependent specifically on sensory inputs from the whiskers, because acute trimming of most whiskers greatly reduces 2DG labeling in both cell classes in columns corresponding to trimmed whiskers. Our results provide confirmation of the active GABAergic cell hypothesis suggested by CO and single-unit data. We conclude that strong activation of inhibitory cortical neurons must confer selective advantages that compensate for its inherent energy inefficiency.
Differential Expression of Distinct Members of Rho Family GTP-Binding Proteins during Neuronal Development: Identification ofRac1B, a New Neural-Specific Member of the Family
Authors: Malosio Maria Luisa , Gilardelli Daniela , Paris Simona , Albertinazzi Chiara , de Curtis Ivan 
Published: April 2018

Previous studies on small GTP-binding proteins of the Rho family have revealed their involvement in the organization of cell actin cytoskeleton. The function of these GTPases during vertebrate development is not known. With the aim of understanding the possible role of these proteins during neuronal development, we have cloned and sequenced five members expressed in developing chick neural retinal cells. We have identified four chicken genes, cRhoA, cRhoB, cRhoC, andcRac1A, homologous to known human genes, and a novelRacgene,cRac1B. Analysis of the distribution of four of the identified transcripts in chicken embryos shows for the first time high levels of expression of Rho family genes in the vertebrate developing nervous system, with distinct patterns of distribution for the different transcripts. In particular,cRhoAandcRac1Agene expression appeared ubiquitous in the whole embryo, and thecRhoBtranscript was more prominent in populations of neurons actively extending neurites, whereas the newly identifiedcRac1Bgene was homogeneously expressed only in the developing nervous system. Temporal analysis of the expression of the five genes suggests a correlation with the morphogenetic events occurring within the developing retina and the retinotectal pathway. Expression of an epitope-tagged cRac1B in retinal neurons showed a diffuse distribution of the protein in the cell body and along neurites.Taken as a whole, our results suggest important roles for ubiquitous and neural-specific members of the Rho family in the acquisition of the mature neuronal phenotype.
Modulation of Force during Locomotion: Differential Action of Crustacean Cardioactive Peptide on Power-Stroke and Return- Stroke Motor Neurons
Authors: Mulloney Brian , Namba Hisaaki , Agricola Hans-Jürgen , Hall Wendy M. 
Published: April 2018

Crustacean cardioactive peptide (CCAP) elicited expression of the motor pattern that drives coordinated swimmeret beating in crayfish and modulated this pattern in a dose-dependent manner. In each ganglion that innervates swimmerets, neurons with CCAP-like immunoreactivity sent processes to the lateral neuropils, which contain branches of swimmeret motor neurons and the local pattern-generating circuits.CCAP affected each of the four functional groups of motor neurons, power-stroke excitors (PSE), return-stroke excitors (RSE), power-stroke inhibitors (PSI), and return-stroke inhibitors (RSI), that innervate each swimmeret. When CCAP was superfused, the membrane potentials of these neurons began to oscillate periodically about their mean potentials. The mean potentials of PSE and RSI neurons depolarized, and some of these neurons began to fire during each depolarization. Both intensity and durations of PSE bursts increased significantly. The mean potentials of RSE and PSI neurons hyperpolarized, and these neurons were less likely to fire during each depolarization. When CCAP was superfused in a low Ca2+saline that blocked chemical transmission, these changes in mean potential persisted, but the periodic oscillations disappeared.These results are evidence that CCAP acts at two levels: activation of local premotor circuits and direct modulation of swimmeret motor neurons. The action on motor neurons is differential; PSEs and RSIs are excited, but RSEs and PSIs are inhibited. The consequences of this selectivity are to increase intensity of bursts of impulses that excite power-stroke muscles.
Modulation of the Parieto-Occipital Alpha Rhythm during Object Detection
Authors: Vanni Simo , Revonsuo Antti , Hari Riitta 
Published: April 2018

Changes in the human neuromagnetic alpha rhythm were monitored during an object detection task to study the effects of visual shape processing on the parieto-occipital activity. Pictures of coherent meaningful objects, which the observers had to detect, and of disorganized meaningless non-objects were presented briefly between masks. The non-objects were systematically followed by a higher level of alpha than the objects, the difference emerging on average 400 msec after the stimulus, with a median delay of 130 msec after evoked response onsets in the occipital, temporal, and parietal cortices. Without attention to visual shape, the alpha levels did not differ between objects and non-objects. The alpha level was higher after non-objects than missed objects, and higher after missed than correctly detected objects, suggesting that the alpha level is inversely related to saliency or familiarity of the object and does not directly reflect visual awareness.The reactive alpha rhythm was generated in the parieto-occipital sulcus, which in several primate species includes areas belonging to the dorsal visual pathway. According to current views, the parietal cortex produces attentional signals that filter out irrelevant information in the ventral visual stream. Our results reinforce the idea of bidirectional interaction: information derived from visual shape can rapidly modify activity in the parieto-occipital region. The synchronized alpha oscillations may reflect attenuation of occipito-parietal information transfer and disengagement of parietal cortex from object selection.
Synchronization of Neuronal Activity during Stimulus Expectation in a Direction Discrimination Task
Authors: de Oliveira Simone Cardoso , Thiele Alexander , Hoffmann Klaus-Peter 
Published: April 2018

The dorsal pathway of the primate brain, especially the middle temporal area (MT or V5) and the superior middle temporal area (MST or V5a), is strongly involved in motion detection. The relation between neural firing rates and psychophysical performance has led to the assumption that the neural code used by these areas consists of the relative discharge rates of neuronal populations. As an additional neural code, temporal correlation of neural activity has been suggested. Our study addresses the involvement of such a code in awake monkeys performing a motion discrimination task.We found significant temporal correlations between simultaneously recorded pairs of units in areas MT and MST and other extrastriate cortical areas. Units recorded from the same electrode were more frequently synchronized than units recorded from different electrodes placed within the same or different cortical areas. Activity synchronization was present in the expectation period before stimulus presentation and could not be inducedde novoby the stimulus. Rather, we found a contrast-dependent reduction of correlation strength on stimulus onset. Correlation strength did not vary systematically with stimulus directions. We conclude that under the conditions of this study, temporal decorrelation of MT and MST neurons could be used to detect the stimulus, but synchronization does not convey specific information about its direction of motion and therefore is unlikely to contribute to performance in our direction discrimination task. Activity synchronization in the period before stimulus onset could be related to attentive expectation.
Dissociable Forms of Inhibitory Control within Prefrontal Cortex with an Analog of the Wisconsin Card Sort Test: Restriction to Novel Situations and Independence from “On-Line” Processing
Authors: Dias R. , Robbins T. W. , Roberts A. C. 
Published: April 2018

Attentional set-shifting and discrimination reversal are sensitive to prefrontal damage in the marmoset in a manner qualitatively similar to that seen in man and Old World monkeys, respectively (Dias et al., 1996b). Preliminary findings have demonstrated that although lateral but not orbital prefrontal cortex is the critical locus inshiftingan attentional setbetweenperceptual dimensions, orbital but not lateral prefrontal cortex is the critical locus inreversinga stimulus–reward associationwithina particular perceptual dimension (Dias et al., 1996a). The present study presents this analysis in full and extends the results in three main ways by demonstrating that (1) mechanisms of inhibitory control and “on-line” processing are independent within the prefrontal cortex, (2) impairments in inhibitory control induced by prefrontal damage are restricted to novel situations, and (3) those prefrontal areas involved in the suppression of previously established response sets are not involved in the acquisition of such response sets.These findings suggest that inhibitory control is a general process that operates across functionally distinct regions within the prefrontal cortex. Although damage to lateral prefrontal cortex causes a loss of inhibitory control in attentional selection, damage to orbitofrontal cortex causes a loss of inhibitory control in affective processing. These findings provide an explanation for the apparent discrepancy between human and nonhuman primate studies in which disinhibition as measured on the Wisconsin Card Sort Test is associated with dorsolateral prefrontal damage, whereas disinhibition as measured on discrimination reversal is associated with orbitofrontal damage.
Induction of Progestin Receptors by Estradiol in the Forebrain of Estrogen Receptor-α Gene-Disrupted Mice
Authors: Moffatt C. A. , Rissman E. F. , Shupnik M. A. , Blaustein J. D. 
Published: April 2018

Mice, rats, and humans have two types of estrogen receptors, estrogen receptor-α (ERα) and estrogen receptor-β (ERβ). Estrogen receptor-α gene-disrupted (ERα-disrupted) mice bear two nonfunctional copies of the ERα gene. This mutation blocks the synthesis of full-length ERα, renders the animals infertile, and inhibits the induction of female sexual behaviors by estradiol and progesterone. It is likely that many of the processes contributing to the regulation of sexual receptivity by estradiol and progesterone are compromised in ERα-disrupted mice. However, given the importance of progesterone in the regulation of sexual receptivity and given the importance of progestin receptors (PRs) in mediating the responses of females to progesterone, we investigated the effects of ERα disruption on the induction of PRs by estradiol in the forebrain.We hypothesized that estradiol would induce PRs in wild-type mice but not in ERα-disrupted mice. Ovariectomized wild-type and ERα-disrupted mice were implanted with either estradiol-filled capsules or empty capsules for 5 d, after which their brains were processed for the immunocytochemical detection of PR. Estradiol increased the number of PR-immunoreactive cells in both wild-type and ERα-disrupted mice. The residual responsiveness of ERα-disrupted mice to estradiol could be accounted for by an ERβ-dependent mechanism or another as yet unidentified estrogen receptor; however, because ERα-immunoreactivity and PCR product representing the 3′ end of ERα mRNA were found in at least one PR-containing region of the ERα-disrupted mice, an ERα splice variant may also mediate the induction of PR-immunoreactivity in ERα-disrupted mice.