@inproceedings{4618, abstract = {We introduce the framework of hybrid automata as a model and specification language for hybrid systems. Hybrid automata can be viewed as a generalization of timed automata, in which the behavior of variables is governed in each state by a set of differential equations. We show that many of the examples considered in the workshop can be defined by hybrid automata. While the reachability problem is undecidable even for very restricted classes of hybrid automata, we present two semidecision procedures for verifying safety properties of piecewiselinear hybrid automata, in which all variables change at constant rates. The two procedures are based, respectively, on minimizing and computing fixpoints on generally infinite state spaces. We show that if the procedures terminate, then they give correct answers. We then demonstrate that for many of the typical workshop examples, the procedures do terminate and thus provide an automatic way for verifying their properties.}, author = {Alur, Rajeev and Courcoubetis, Costas and Henzinger, Thomas A and Ho, Pei}, booktitle = {Hybrid Systems}, editor = {Grossman, Robert and Nerode, Anil and Ravn, Anders and Rischel, Hans}, pages = {209 -- 229}, publisher = {Springer}, title = {{Hybrid automata: An algorithmic approach to the specification and verification of hybrid systems}}, doi = {10.1007/3-540-57318-6_30}, volume = {736}, year = {1993}, } @inproceedings{4619, abstract = {Traditional approaches to the algorithmic verification of real-time systems are limited to checking program correctness with respect to concrete timing properties (e.g., "message delivery within 10 milliseconds"). We address the more realistic and more ambitious problem of deriving symbolic constraints on the timing properties required of real-time systems (e.g., "message delivery within the time it takes to execute two assignment statements"). To model this problem, we introduce parametric timed automata -- finite-state machines whose transitions are constrained with parametric timing requirements. The emptiness question for parametric timed automata is central to the verification problem. On the negative side, we show that in general this question is undecidable. On the positive side, we provide algorithms for checking the emptiness of restricted classes of parametric timed automata. The practical relevance of these classes is illustrated with several verification examples. There remains a gap between the automata classes for which we know that emptiness is decidable and undecidable, respectively, and this gap is related to various hard and open problems of logic and automata theory.}, author = {Alur, Rajeev and Henzinger, Thomas A and Vardi, Moshe}, booktitle = {Proceedings of the 25th annual ACM symposium on Theory of Computing}, location = {San Diego, CA, United States of America}, pages = {592 -- 601}, publisher = {ACM}, title = {{Parametric real-time reasoning}}, doi = {10.1145/167088.167242}, year = {1993}, } @inproceedings{4620, abstract = {We present a verification algorithm for duration properties of finite-state real-time systems. While simple real-time properties constrain the total elapsed time between events, duration properties constrain the accumulated time during which certain state predicates hold. We formalize the concept of durations by introducing duration measures for (dense-time) timed automata. Given a timed automaton with a duration measure, a start and a target state, and a duration constraint, the duration-bounded reachability problem asks if there is a run of the automaton from the start state to the target state such that the accumulated duration along the run satisfies the constraint. Our main result is a novel decision procedure for solving the duration-bounded reachability problem. We also prove that the problem is PSPACE-complete and demonstrate how the solution can be used to verify interesting duration properties of real-time systems.}, author = {Alur, Rajeev and Courcoubetis, Costas and Henzinger, Thomas A}, booktitle = {5th International Conference on Computer Aided Verification}, location = {Elounda, Greece}, pages = {181 -- 193}, publisher = {Springer}, title = {{Computing accumulated delays in real-time systems}}, doi = {10.1007/3-540-56922-7_16}, volume = {697}, year = {1993}, } @article{2487, abstract = {Distribution of the mRNA for a metabotropic glutamate receptor, mGluR3, which is coupled to the inhibitory cAMP cascade, was examined in the central nervous system of the adult albino rat by in situ hybridization. The hybridization signals of mGluR3 were detected not only on neuronal cells but also on many glial cells throughout the brain and spinal cord. In the neuronal cells, prominent expression of mGluR3 mRNA was seen in the thalamic reticular nucleus. Moderately labeled neurons were seen in the anterior olfactory nucleus, cerebral neo- and mesocortical regions, lateral amygdaloid nucleus, ventral part of the basolateral amygdaloid nucleus, dorsal endopiriform nucleus, supraoptic nucleus, superficial layers of the superior colliculus, inferior colliculus, interpeduncular nucleus, superior olivary nuclei, and Golgi cells in the cerebellar cortex. Weakly labeled neurons were observed in the striatum, nucleus accumbens, ventral pallidum, globus pallidus, entopeduncular nucleus, lateral hypothalamic area, hypothalamic paraventricular nucleus, medial habenular nucleus, anterior pretectal nucleus, Barrington's nucleus, Nucleus O, paragenual nucleus, trigeminal sensory complex, cochlear nuclei, dorsal motor nucleus of the trigeminal nerve, dorsal cap of the inferior olive, spinal dorsal horn, and lamina X of the spinal cord. The stellate cells in the cerebellar cortex, and neurons in the deep cerebellar nuclei were also labeled weakly. The granule cell layer of the dentate gyrus, as a whole, appeared to be labeled intensely, but each of the granule cells was labeled only weakly. No significant labeling was detected in the mitral and tufted cells in the olfactory bulb, hippocampal pyramidal cells, Purkinje and granule cells in the cerebellar cortex, or somatic motoneurons. The distribution of mGluR3 mRNA in particular neurons and glial cells indicates specific roles of mGluR3 in the glutamatergic system of the central nervous system.}, author = {Ohishi, Hitoshi and Shigemoto, Ryuichi and Nakanishi, Shigetada and Mizuno, Noboru}, issn = {0021-9967}, journal = {Journal of Comparative Neurology}, number = {2}, pages = {252 -- 266}, publisher = {Wiley-Blackwell}, title = {{ Distribution of the mRNA for a metabotropic glutamate receptor (mGluR3) in the rat brain: An in situ hybridization study}}, doi = {10.1002/cne.903350209}, volume = {335}, year = {1993}, } @article{2536, abstract = {A cDNA clone for a new metabotropic glutamate receptor, termed mGluR6, was isolated from a rat retinal cDNA library by cross-hybridization with the previously isolated cDNA clone for a metabotropic glutamate receptor. The cloned mGluR6 subtype consists of 871 amino acid residues and exhibits a structural architecture common to the metabotropic receptor family, possessing a large extracellular domain preceding the seven putative membrane-spanning domains. mGluR6 shows the highest sequence similarity to mGluR4 among the metabotropic receptor subtypes and inhibits the forskolin- stimulated cyclic AMP accumulation in Chinese hamster ovary cells transfected with the cloned cDNA. mGluR6 potently reacts with L-2-amino-4- phosphonobutyrate (L-AP4) and L-serine-O-phosphate, and the potencies of these compounds are one order of magnitude greater than that of L-glutamate. Blot and in situ hybridization analyses indicated that mGluR6 mRNA is restrictedly expressed in the inner nuclear layer of the retina where ON- bipolar cells are distributed. The metabotropic receptor that responds strongly to L-AP4 and L-serine-O-phosphate in ON-bipolar cells is known to mediate glutamate synaptic transmission between photoreceptor cells and ON- bipolar cells. On the basis of the agonist selectivity of mGluR6 and its specific expression in retinal cells, the physiological role of this receptor subtype in the visual system is discussed.}, author = {Nakajima, Yoshiaki and Iwakabe, Hideki and Akazawa, Chihiro and Nawa, Hiroyuki and Shigemoto, Ryuichi and Mizuno, Noboru and Nakanishi, Shigetada}, issn = {0021-9258}, journal = {Journal of Biological Chemistry}, number = {16}, pages = {11868 -- 11873}, publisher = {American Society for Biochemistry and Molecular Biology}, title = {{Molecular characterization of a novel retinal metabotropic glutamate receptor mGluR6 with a high agonist selectivity for L-2-amino-4- phosphonobutyrate}}, doi = {10.1016/S0021-9258(19)50280-0}, volume = {268}, year = {1993}, } @article{2537, abstract = {The metabotropic glutamate receptors are coupled to intracellular signal transduction via G-proteins and consist of a family of at least five different subtypes, termed mGluR1-mGluR5. We studied the signal transduction mechanism and pharmacological characteristics of the rat mGluR3 and mGluR4 subtypes in Chinese hamster ovary cells permanently expressing the cloned receptors. Both mGluR3 and mGluR4 inhibit the forskolin-stimulated accumulation of intracellular cAMP formation in response to agonist interaction. Consistent with the high degree of sequence similarity to mGluR2, mGluR3 closely resembles mGluR2 in its agonist selectivity; the potency rank order of agonists is L-glutamate > trans-1-aminocyclopentane- 1,3-dicarboxylate > ibotenate > quisqualate. mGluR4 is totally different in its agonist specificity from any other member of the metabotropic receptors. This receptor potently reacts with L-2-amino-4-phosphonobutyrate(L-AP4) in a stereo-selective manner and moderately responds to L-serine-O-phosphate. mGluR4 thus corresponds well to the putative L-AP4 receptor characterized from brain preparations. Blot and in situ hybridization analyses indicated that both mRNAs are widely distributed in the rat brain. mGluR3 mRNA is highly expressed in neuronal cells of the cerebral cortex and the caudate- putamen, and in granule cells of the hippocampal dentate gyrus. The expression pattern of mGluR4 mRNA is more restricted, and this expression is prominent in the cerebellum, olfactory bulb, and thalamus. Furthermore, the mGluR3 mRNA, unlike the other mRNAs for the metabotropic receptors, is highly expressed in glial cells throughout the brain regions. The metabotropic glutamate receptor subtypes can thus be classified into three subgroups according to the similarity in their amino acid sequences, signal transduction, and agonist selectivity: mGluR1/mGluR5, mGluR2/mGluR3, and mGluR4. The mRNAs for the individual receptor subtypes, however, show overlapping but distinct patterns of expression in the rat CNS.}, author = {Tanabe, Yasuto and Nomura, Akinori and Masu, Masayuki and Shigemoto, Ryuichi and Mizuno, Noboru and Nakanishi, Shigetada}, issn = {0270-6474}, journal = {Journal of Neuroscience}, number = {4}, pages = {1372 -- 1378}, publisher = {Society for Neuroscience}, title = {{Signal transduction, pharmacological properties, and expression patterns of two rat metabotropic glutamate receptors, mGluR3 and mGluR4}}, doi = {10.1523/JNEUROSCI.13-04-01372.1993}, volume = {13}, year = {1993}, } @article{2538, abstract = {Rat mRNAs encoding two subtypes of the endothelin (ET) receptor (ET(A) and ET(B)) were studied in the rat ovary and fallopian tube by means of Northern blotting and in situ hybridization. The mRNA transcripts for the endothelin- 1-specific type receptor (ET(A)) in pooled RNA from the ovary and fallopian tube were 4.2 and 5.2 kilonucleotides, and that for the nonselective type receptor (ET(B)) was 4.7 kilonucleotides; these were similar to transcripts for endothelin receptors from other tissues. ET(A) mRNA expression was abundant in the muscle cell layer of the fallopian tube, but low in the ovary. On the other hand, ET(B) mRNA was abundant in the granulosa cells in the developing follicles, but low in atretic follicles and absent in the fallopian tube. These results demonstrated that the mRNAs for the two subtypes of the rat endothelin receptor have different expression profiles in the ovary and fallopian tube. ETs may mainly affect the granulosa cells in the dominant follicles as well as the muscle cells of the fallopian tube through ET(B) and ET(A), respectively.}, author = {Iwai, Masazumi and Hori, Seiji and Shigemoto, Ryuichi and Kanzaki, Hideharu and Mori, Takahide and Nakanishi, Shigetada}, issn = {0006-3363}, journal = {Biology of Reproduction}, number = {4}, pages = {675 -- 680}, publisher = {Society for the Study of Reproduction}, title = {{Localization of endothelin receptor messenger ribonucleic acid in the rat ovary and fallopian tube by in situ hybridization}}, doi = {10.1095/biolreprod49.4.675}, volume = {49}, year = {1993}, } @article{2539, abstract = {cDNA clones for four different N-methyl-D-aspartate (NMDA) receptor subunits (NMDAR2A-NMDAR2D) were isolated through polymerase chain reactions followed by molecular screening of a rat brain cDNA library. These subunits are only about 15% identical with the key subunit of the NMDA receptor (NMDAR1) but are highly homologous (~50% homology) with one another. They also commonly possess large hydrophilic domains at both amino- and carboxyl- terminal sides of the four putative transmembrane segments. NMDAR2A and NMDAR2C expressed individually in Xenopus oocytes showed no electrophysiological response to agonists. However, these subunits in combined expression with NMDAR1 markedly potentiated the NMDAR1 activity and produced functional variability in the affinity of agonists, the effectiveness of antagonists, and the sensitivity to Mg2+ blockade. Thus, NMDAR1 is essential for the function of the NMDA receptor, and multiple NMDAR2 subunits potentiate and differentiate the function of the NMDA receptor by forming different heteromeric configurations with NMDAR1. Northern blotting and in situ hybridization analyses revealed that the expressions of individual mRNAs for the NMDAR2 subunits overlap in some brain regions but are also specialized in many other regions. This investigation demonstrates the anatomical and functional differences of the NMDAR2 subunits, which provide the molecular basis for the functional diversity of the NMDA receptor.}, author = {Ishii, Takahiro and Moriyoshi, Koki and Sugihara, Hidemitsu and Sakurada, Kazuhir and Kadotani, Hiroshi and Yokoi, Mineto and Akazawa, Chihiro and Shigemoto, Ryuichi and Mizuno, Noboru and Masu, Masayuki and Nakanishi, Shigetada}, issn = {0021-9258}, journal = {Journal of Biological Chemistry}, number = {4}, pages = {2836 -- 2843}, publisher = {American Society for Biochemistry and Molecular Biology}, title = {{Molecular characterization of the family of the N-methyl-D-aspartate receptor subunits}}, doi = {10.1016/s0021-9258(18)53849-7 }, volume = {268}, year = {1993}, } @article{2540, abstract = {Distribution of the messenger RNA for a metabotropic glutamate receptor, mGluR2, which is coupled to the inhibitory cyclic AMP cascade, was investigated in the central nervous system of the adult rat by in situ hybridization. Transcripts of mGluR2 were specifically localized to neuronal cells of the brain. Although the hybridization signals were widely distributed in the brain, the most prominent expression of mGluR2 messenger RNA was seen in Golgi cells of the cerebellum. Marked expression of mGluR2 messenger RNA was further observed in the mitral cells of the accessory olfactory bulb, neurons in the external part of the anterior olfactory nucleus, and pyramidal neurons in the entorhinal and parasubicular cortical regions. The granule cells of the accessory olfactory bulb, and many pyramidal and non-pyramidal neurons in the neocortical, cingulate, retrosplenial and subicular cortices, were moderately labeled. All of the granule cells in the dentate gyrus were also labeled moderately, whereas no significant hybridization signals were detected in Ammon's horn. In the basal forebrain regions, moderately labeled neurons were distributed in the triangular septal nucleus, in the lateral, basolateral and basomedial amygdaloid nuclei, and in the medial mammillary nucleus. Weakly labeled neurons were sparsely scattered in the striatum, globus pallidus, ventral pallidum and claustrum. The subthalamic nucleus was also labeled weakly. No significant labeling was found in the entopeduncular nucleus and substantia nigra. In the thalamus, moderately labeled neurons were distributed in the anterodorsal, anteromedial, ventromedial, intralaminar and midline nuclei; the ventrolateral part of the anteroventral nucleus and the rostral pole of the ventrolateral nucleus also contained moderately labeled neurons. No significant labeling was found in the thalamic reticular, submedius, ventroposterior, lateral geniculate and medial geniculate nuclei. In the lower brainstem, labeling was generally weak. No significant hybridization signals were found in the spinal cord. Some neurons in the inner part of the inner nuclear layer of the retina and some retinal ganglion cells were labeled moderately. The pattern of distribution of mGluR2 messenger RNA revealed in the present study indicates specific roles of mGluR2 in the glutamatergic system in the brain.}, author = {Ohishi, Hitoshi and Shigemoto, Ryuichi and Nakanishi, Shigetada and Mizuno, Noboru}, issn = {0306-4522}, journal = {Neuroscience}, number = {4}, pages = {1009 -- 1018}, publisher = {Elsevier}, title = {{Distribution of the messenger RNA for a metabotropic glutamate receptor, mGluR2, in the central nervous system of the rat}}, doi = {10.1016/0306-4522(93)90485-X}, volume = {53}, year = {1993}, } @article{2541, abstract = {A trp E fusion protein containing a C-terminal portion of the rat substance P receptor (SPR) was expressed in bacteria and used to produce an antibody. The antibody specifically reacted with SPR expressed in a mammalian cell line and rat striatum. Light and electron microscope analyses of the rat striatum revealed intense SPR-like immunoreactivity in neuronal somata and dendrites. These immunoreactive neurons constituted ∼ 3% of the total population of striatal neurons; they were putative interneurons of large and medium-sized aspiny types.}, author = {Shigemoto, Ryuichi and Nakaya, Yoshifumi and Nomura, Sakashi and Ogawa Meguro, Reiko and Ohishi, Hitoshi and Kaneko, Takeshi and Nakanishi, Shigetada and Mizuno, Noboru}, issn = {0304-3940}, journal = {Neuroscience Letters}, number = {2}, pages = {157 -- 160}, publisher = {Elsevier}, title = {{Immunocytochemical localization of rat substance P receptor in the striatum}}, doi = {10.1016/0304-3940(93)90311-8}, volume = {153}, year = {1993}, } @article{2542, abstract = {A trpE-fusion protein containing a C-terminal sequence of a rat metabotropic glutamate receptor, mGluR5, was used to produce an antibody. On immunoblot, the antibody specifically reacted with mGluR5 expressed in mammalian cells and rat brain. Immunohistochemical analysis revealed intense mGluR5-like immunoreactivity (LI) in the olfactory bulb, anterior olfactory nuclei, olfactory tubercle, cerebral cortex, hippocampus, lateral septum, striatum, nucleus accumbens, inferior colliculus, and spinal trigeminal nuclei. The distribution pattern of mGluR5-LI corresponds very well with that of mGluR5 mRNA. Electron microscope analysis of the striatum revealed dense accumulation of immunoreaction products in dendrites which were often provided with asymmetrical synapses. These results suggest that mGluR5 is predominantly located in postsynaptic elements.}, author = {Shigemoto, Ryuichi and Nomura, Sakashi and Ohishi, Hitoshi and Sugihara, Hidemitsu and Nakanishi, Shigetada and Mizuno, Noboru}, issn = {0304-3940}, journal = {Neuroscience Letters}, number = {1}, pages = {53 -- 57}, publisher = {Elsevier}, title = {{Immunohistochemical localization of a metabotropic glutamate receptor, mGluR5, in the rat brain}}, doi = {10.1016/0304-3940(93)90227-C}, volume = {163}, year = {1993}, } @article{2543, abstract = {Pituitary adenylate cyclase-activating polypeptide (PACAP) is a polypeptide hormone related to vasoactive intestinal polypeptide (VIP). Rat PACAP receptor cDNA was isolated from a brain cDNA library by cross-hybridization with rat VIP receptor cDNA. The recombinant PACAP receptor expressed in COS cells bound PACAP with about 1000 times higher affinity than VIP, and PACAP stimulated adenylate cyclase through the cloned PACAP receptor. The rat PACAP receptor consists of 495 amino acids, contains seven transmembrane segments, and has a significant similarity with other Gs-coupled receptors, such as VIP, glucagon, and secretin receptors. PACAP receptor mRNA was abundantly expressed in the brain, but not in the peripheral tissues except for the adrenal gland. In situ hybridization revealed a high level of expression of PACAP receptor mRNA in the hippocampal dentate gyrus, olfactory bulb, and cerebellar cortex.}, author = {Hashimoto, Hitoshi and Ishihara, Takeshi and Shigemoto, Ryuichi and Mori, Kensaku and Nagata, Shigekazu}, issn = {0896-6273}, journal = {Neuron}, number = {2}, pages = {333 -- 342}, publisher = {Elsevier}, title = {{ Molecular cloning and tissue distribution of a receptor for pituitary adenylate cyclase-activating polypeptide}}, doi = {10.1016/0896-6273(93)90188-W}, volume = {11}, year = {1993}, } @article{2544, abstract = {VARIOUS functions of glutamate transmission are mediated by both ionotropic and metabotropic glutamate receptors1. The metabotropic glutamate receptors (mGluRs) consist of at least six different subtypes that are classified into three subgroups, mGluR1/mGluR5, mGluR2/mGluR3, and mGluR4/mGluR6 (refs 1-5), but their physiological roles are largely unknown. Here we report the identification of a very potent agonist for mGluR2/mGluR3, DCG-IV, and the specific localization of mGluR2 in granule cell dendrites that form dendrodendritic synapses with mitral cells in the accessory olfactory bulb. Using the DCG-IV agonist for mGluR2 in combination with slice patchrecording, we demonstrate that the granule cell mGluR2 presynaptically suppresses inhibitory GABA (γ-aminobutyrate) transmission to the mitral cell. Our results indicate that mGluR2 in granule cells plays an important role in the persistent excitation of olfactory sensory transmission in the accessory olfactory bulb by relieving mitral cells from the GABA inhibition.}, author = {Hayashi, Yasunori and Momiyama, Akiko and Takahashi, Tomoyuki and Ohishi, Hitoshi and Ogawa Meguro, Reiko and Shigemoto, Ryuichi and Mizuno, Noboru and Nakanishi, Shigetada}, issn = {0028-0836}, journal = {Nature}, number = {6456}, pages = {687 -- 690}, publisher = {Nature Publishing Group}, title = {{Role of a metabotropic glutamate receptor in synaptic modulation in the accessory olfactory bulb}}, doi = {10.1038/366687a0}, volume = {366}, year = {1993}, } @article{2546, abstract = {Immunochemical characteristics of neostriatal neurons producing substance P receptor (SPR) were examined in adult rats by double- and triple-immunofluorescence methods. In the neostriatum, SPR immunoreactivity was detected in large and medium-sized aspiny neurons. Virtually all SPR-immunoreactive neurons in the neostriatum contained somatostatin (SS) or choline acetyltransferase (ChAT), but not parvalbumin. All SS- and ChAT-immunoreactive neurons in the neostriatum showed SPR immunoreactivity. The co-existence of SS and ChAT was, however, not found in single neurons expressing SPR immunoreactivity. The present results indicate that neostriatal neurons immunoreactive for SPR are segregated into 2 groups: (1) medium-sized, aspiny somatostatinergic, and (2) large, aspiny cholinergic neurons.}, author = {Kaneko, Takeshi and Shigemoto, Ryuichi and Nakanishi, Shigetada and Mizuno, Noboru}, issn = {0006-8993}, journal = {Brain Research}, number = {2}, pages = {297 -- 303}, publisher = {Elsevier}, title = {{Substance P receptor-immunoreactive neurons in the rat neostriatum are segregated into somatostatinergic and cholinergic aspiny neurons}}, doi = {10.1016/0006-8993(93)91548-7}, volume = {631}, year = {1993}, } @article{2723, abstract = {The ground-state density of the Pauli operator in the case of a nonconstant magnetic field with constant direction is studied. It is shown that in the large field limit, the naturally rescaled ground-state density function is bounded from above by the megnetic field, and under some additional conditions, the limit density function is equal to the magnetic field. A restatement of this result yields an estimate on the density of complex orthogonal polynomials with respect to a fairly general weight function. We also prove a special case of the paramagnetic inequality. }, author = {Erdös, László}, issn = {0377-9017}, journal = {Letters in Mathematical Physics}, number = {3}, pages = {219 -- 240}, publisher = {Springer}, title = {{Ground-state density of the Pauli operator in the large field limit}}, doi = {10.1007/BF00761110}, volume = {29}, year = {1993}, } @article{1945, abstract = {The effects of ultra-low (10(-18)-10(-14) M) doses (ULD) of biologically active substances have been reviewed in terms of common regularities of ULD effects and peculiarities of action of various groups of compounds. The most common and at the same time paradoxical regularities of ULD action are bi- or polymodal patterns of dose dependence, absence or presence of an inverse effect at higher doses, and instability of ULD effect. Possible mechanisms of ULD action including the mechanism based on the adaptation theory are discussed.}, author = {Sazanov, Leonid A and Zaǐtsev, Sergei}, issn = {0006-2979}, journal = {Biochemistry (Moscow)}, number = {10}, pages = {1443 -- 1460}, publisher = {Izdatel'stvo Nauka}, title = {{Effect of superlow doses (10(-18)-10-(-14) M) of biologically active substances: general rules, features, and possible mechanisms}}, volume = {57}, year = {1992}, } @article{3469, abstract = {Glutamate-operated ion channels (GluR channels) of the L-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-kainate subtype are found in both neurons and glial cells of the central nervous system. These channels are assembled from the GluR-A, -B, -C, and -D subunits; channels containing a GluR-B subunit show an outwardly rectifying current-voltage relation and low calcium permeability, whereas channels lacking the GluR-B subunit are characterized by a doubly rectifying current-voltage relation and high calcium permeability. Most cell types in the central nervous system coexpress several subunits, including GluR-B. However, Bergmann glia in rat cerebellum do not express GluR-B subunit genes. In a subset of cultured cerebellar glial cells, likely derived from Bergmann glial cells. GluR channels exhibit doubly rectifying current-voltage relations and high calcium permeability, whereas GluR channels of cerebellar neurons have low calcium permeability. Thus, differential expression of the GluR-B subunit gene in neurons and glia is one mechanism by which functional properties of native GluR channels are regulated.}, author = {Burnashev, Nail and Khodorova, Alla and Jonas, Peter M and Helm, P. and Wisden, William and Monyer, Hannah and Seeburg, Peter and Sakmann, Bert}, issn = {0036-8075}, journal = {Science}, number = {5063}, pages = {1566 -- 1570}, publisher = {American Association for the Advancement of Science}, title = {{Calcium-permeable AMPA-kainate receptors in fusiform cerebellar glial cells.}}, doi = {10.1126/science.1317970}, volume = {256}, year = {1992}, } @article{3470, abstract = {Currents activated by glutamate receptor (GluR) agonists were recorded from outside-out patches isolated from the soma of visually identified pyramidal neurones of the (CA3 and CA1 region of rat hippocampal slices. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). L-glutamate (L-Glu), and kainate (KA) were delivered either by bath application through perfusion of the recording chamber or by rapid application via a piezo-driven two-barrelled fast application system. 2. Bath application of each of the three agonists activated inward currents in all patches (n = 134) at holding potentials of -50 or -60 mV. The current amplitude increased in size between 3 to 30 μM-AMPA and 100 μM to 1 mM-KA. With this slow mode of bath application, the responses showed no apparent desensitization even at saturating concentrations of AMPA (30 μM) and KA (1 mM). 3. The ratio of currents activated by 30 μM-AMPA and 300 μM-KA showed a characteristic difference between CA3 and CA1 neurones. The ratio was 0.242 ± 0.028 (mean ± S.E.M., n = 16) for CA3 cell patches and 0.097 ± 0.012 (n = 8) for CA1 cell patches indicating that GluRs in the two cell populations are different. 4. The steady-state current-voltage relations (I-Vs) for AMPA- and KA-activated currents showed pronounced outward rectification for both cell types (when the main cations are Na+ in the bath and Cs+ in the pipette solution). The current reversed close to 0 mV and the ratio of chord conductances 80 mV on either side of the reversal potential was 2.66 for KA-activated currents in CA3 cell patches and 2.60 in CA1 cell patches. AMPA-activated currents showed a time-dependent increase after steps to positive membrane potentials and a decrease after steps to negative voltages, indicating that a gating process is responsible for outward rectification of the steady-state I-IV. 5. The permeability (P) of GluR channels was high for Na+ as compared to Cs+ for both cell types (P(Na)/P(Cs) = 0.88 and 0.84). The permeability was low for N-methyl-D-glucamine+ (P(NMG)/P(Cs) ≤ 0.03) and Ca2+ (P(Ca)/P(Cs) ≤0.05). 6. The current noise level increased during application of AMPA or KA. Apparent single-channel conductances obtained from fluctuation analysis were higher for AMPA than for KA, but similar for both cell types. In CA3 cell patches, AMPA activated channels with an apparent chord conductance of 7.2 pS, KA of 3.0 pS conductance. 7. Fast agonist application revealed desensitization of GluR channels which was dependent on the type of agonist, currents activated by AMPA and L-Glu rose rapidly to a peak and then desensitized to a steady-state current. In contrast, currents activated by fast application of KA rose to a plateau and did not desensitize. The steady state current expressed as a percentage of the peak current was higher for L-Glu than for AMPA and slightly higher for CA3 than for CA1 cell patches. For CA3 cell patches, this fraction amounted to 6.2 %, with 300 μM-L-Glu and 2.8%, with 300 μM-AMPA. For CA1 cell patches, corresponding values were 3.6 and 1.9 % 8. The dose response relations for the peak current activated by AMPA and L-Glu and the steady-state current activated by KA were similar for CA3 and CA1 cell patches. The order of potency was AMPA > L-Glu ≃ KA for both cell types EC50 values 189, 342 and 344 μM for CA3 cell patches and 183, 424 and 474 μM for CA1 cell patches). In all cases, the Hill coefficients ranged between 12 and 1.7. 8. The rise of AMPA and L-Glu-activated currents became faster with increasing agonist concentration for both cell types. With L-Glu, rise times decreased from about 3 ms at 100 μM to 500 μs at 3 mM. The delay for agonist concentrations ≥ 300 μM was described by the sum of two exponential functions. The time constant of the predominant fast component was slightly concentration dependent and decreased from about 12 ms at 300 μM to 8 ms at 3 mM-L-Glu. 10. The current voltage relations of the peak currents activated by 300 μM-AMPA were linear for both cell types with a reversal potential close to OmV. 11. It is concluded that the GluR channels in pyramidal cells of hippocampal CA3 and CA1 regions are distinet but share many pharmacological and functional properties. Comparison of the properties of native and recombinant GluRs suggests that in both CA3 and CA1 regions GluR channels are hetero-oligomers containing the GluR-B subunit.}, author = {Jonas, Peter M and Sakmann, Bert}, issn = {0022-3751}, journal = {Journal of Physiology}, pages = {143 -- 171}, publisher = {Wiley-Blackwell}, title = {{Glutamate receptor channels in isolated patches from CA1 and CA3 pyramidal cells of rat hippocampal slices}}, doi = {10.1113/jphysiol.1992.sp019294 }, volume = {455}, year = {1992}, } @article{3471, abstract = {1. Outside-out patches were isolated from granule cells of dentate gyrus and pyramidal cells of CA3 and CA1 regions of rat hippocampal slices. Patches were exposed briefly to L-glutamate using a piezo-driven double-barrelled application pipette. 2. Applications of glutamate (1 mM) of 1 ms duration activated patch currents which rose and decayed rapidly. The 20-80% rise time of these glutamate receptor (GluR)-mediated currents was usually 0.2-0.6 ms. At -50 mV the peak current varied from 10 to 500 pA in different patches. 3. The peak current-voltage relation for brief pulses of 1 mM glutamate was virtually linear in normal extracellular solution for patches from the three cell types (-100 to 60 mV). 4. The permeability of GluR channels activated at the peak to Ca2+, relative to K+, was less than 0.1 for all three cell types (under bi-ionic conditions with Ca2+ on the extracellular side and K+ on the intracellular side of the membrane). 5. The offset decay time constant of the current following 1 ms pulses of 1 mM glutamate was brief, with mean values of 3.0 +/- 0.8, 2.5 +/- 0.7, and 2.3 +/- 0.7 ms for dentate, CA3 and CA1 cell patches, respectively. Offset time constants were independent of membrane potential and independent of glutamate concentration (200 microM and 1 mM) for the three cell types. 6. Applications of 1 mM glutamate of 100 ms duration showed that glutamate responses desensitized rapidly. The time constants for desensitization were 9.4 +/- 2.7, 11.3 +/- 2.8, and 9.3 +/- 2.8 ms for patches from dentate, CA3 and CA1 cells respectively. Desensitization time constants were only weakly dependent on glutamate concentration (200 microM and 1 mM) for the three cell types. Thus offset time constants are about four times faster than desensitization time constants for both glutamate concentrations. 7. Double pulse application of glutamate indicated that even a 1 ms pulse of 1 mM glutamate causes partial (about 60%) desensitization of GluR channels. The time course of recovery from desensitization was slower in dentate gyrus granule cell patches than in CA3 or CA1 pyramidal cell patches. 8. Desensitization was studied at equilibrium by exposing patches to low glutamate concentrations for at least 15 s before a 1 ms test pulse of 1 mM glutamate.}, author = {Colquhoun, D. and Jonas, Peter M and Sakmann, Bert}, issn = {0022-3751}, journal = {Journal of Physiology}, pages = {261 -- 287}, publisher = {Wiley-Blackwell}, title = {{Action of brief pulses of glutamate on AMPA/kainate receptors in patches from different neurones of rat hippocampal slices}}, doi = {10.1113/jphysiol.1992.sp019417}, volume = {458}, year = {1992}, } @article{3472, abstract = {A novel potassium-selective channel which is active at membrane potentials between -100 mV and +40 mV has been identified in peripheral myelinated axons of Xenopus laevis using the patch-clamp technique. At negative potentials with 105 mM-K on both sides of the membrane, the channel at 1 kHz resolution showed a series of brief openings and closings interrupted by longer closings, resulting in a flickery bursting activity. Measurements with resolution up to 10 kHz revealed a single-channel conductance of 49 pS with 105 mM-K and 17 pS with 2.5 mM-K on the outer side of the membrane. The channel was selective for K ions over Na ions (PNa/PK = 0.033). The probability of being within a burst in outside-out patches varied from patch to patch (> 0.2, but often > 0.9), and was independent of membrane potential. Open-time histograms were satisfactorily described with a single exponential (tau o = 0.09 msec), closed times with the sum of three exponentials (tau c = 0.13, 5.9, and 36.6 msec). Sensitivity to external tetraethylammonium was comparatively low (IC50 = 19.0 mM). External Cs ions reduced the apparent unitary conductance for inward currents at Em = -90 mV (IC50 = 1.1 mM). Ba and, more potently, Zn ions lowered not only the apparent single-channel conductance but also open probability. The local anesthetic bupivacaine with high potency reduced probability of being within a burst (IC50 = 165 nM). The flickering K channel is clearly different from the other five types of K channels identified so far in the same preparation. We suggest that this channel may form the molecular basis of the resting potential in vertebrate myelinated axons.}, author = {Koh, Duk and Jonas, Peter M and Bräu, Michael and Vogel, Werner}, issn = {0022-2631}, journal = {Journal of Membrane Biology}, pages = {149 -- 162}, publisher = {Springer}, title = {{A TEA-insensitive flickering potassium channel active around the resting potential in myelinated nerve}}, doi = {10.1007/BF00231893}, volume = {130}, year = {1992}, }