Different mechanisms regulate IPSC kinetics in early postnatal and juvenile hippocampal granule cells.

1. Monosynaptic inhibitory postsynaptic currents (IPSCs) were recorded from early postnatal and juvenile dentate granule cells in rat brain slices at room temperature. The focally evoked currents were mediated by gamma-aminobutyric acid-A (GABAA) receptors.

Blockade of voltage-gated outward K+ currents of ramified murine microglia by scorpion peptide toxins.

Microglial cells were cultured from murine neonatal brain. Ramification of isolated microglia could be induced by the application of astrocyte-conditioned medium (ACM). Voltage-gated outward potassium currents (IK) were measured in ramified microglial cells 12-24 h after their treatment with ACM.

Repetitive spreading depression causes selective suppression of GABAergic function.

Cortical spreading depression (SD) represents a pathophysiological signal that has been associated with the induction of migraine and ischaemic brain damage. The properties of repetitive SDs and their effects on excitatory and inhibitory synaptic transmission were analysed in neocortical slices obtained from adult rats. The SD showed only small variations in amplitude, duration and integral when elicited four times at intervals of 30 min.

Comparison of effects induced by toxic applications of kainate and glutamate by glucose deprivation on area CA1 of rat hippocampal slices.

Baseline and stimulus-induced changes in [Ca2+]o and [K+]o as well as field potentials (fp's) were studied during application of the excitatory amino acids kainate or glutamate, or during glucose deprivation in area CA1 and CA3 of rat hippocampal slices. Bath application of kainate in concentrations of 1, 2, 5, 8 and 10 mM induced a sudden rapid fall of [Ca2+]o in area CA1, associated with a negative shift of the slow fp. Kainate induced disappearance of stratum radiatum (SR) as well as alveus stimulation-evoked postsynaptic fp's, with partial recovery after application of up to 2 mM kainate, but no recovery after 5 mM kainate.

Effects of serotonin on different patterns of low Mg(2+)-induced epileptiform activity in the subiculum of rats studied in vitro.

The subiculum is an epilepsy-prone area within the hippocampal complex that receives a dense serotonergic innervation from the raphe nuclei. We investigated the effect of 5-HT on epileptiform activity in this region with intra- and extracellular recordings. Our data suggest that 5-HT has predominately inhibitory effects on epileptiform activity in the subiculum but in some cases could also function as a disinhibitory agent.

Effects of gamma-aminobutyric acid (GABA) agonists and GABA uptake inhibitors on pharmacosensitive and pharmacoresistant epileptiform activity in vitro.

1. Lowering of the extracellular Mg(2+)-concentration induces various patterns of epileptiform activity in combined rat entorhinal cortex-hippocampal brain slices. After a prolonged period of exposure to Mg(2+)-free medium seizure-like events in the entorhinal cortex change to a state of late recurrent discharges which cannot be blocked by clinically available antiepileptic drugs.

Spread of low Mg2+ induced epileptiform activity from the rat entorhinal cortex to the hippocampus after kindling studied in vitro.

Extracellular recordings were performed in in vitro combined hippocampal-entorhinal cortex (HC-EC) slices obtained from control and amygdala kindled rats to investigate the spread of epileptiform activity from the entorhinal cortex (EC) to the hippocampus (HC). Epileptiform activity was induced by lowering extracellular Mg2+ concentration. In control slices epileptiform activity was in most slices characterized by intericatal discharges and short recurrent discharges in areas CA1 and CA3 and by early seizure like events and late recurrent discharges in the EC and the subiculum.

Properties of a delayed rectifier potassium current in dentate granule cells isolated from the hippocampus of patients with chronic temporal lobe epilepsy.

Purpose: Properties of potassium outward currents were investigated in human hippocampal dentate gyrus granule cells from 11 hippocampal specimens obtained from patients with temporal lobe epilepsy (TLE) during resective surgery.

Methods: Dentate granule cells were isolated enzymatically and outward currents analyzed by using the whole-cell configuration of the patch-clamp method. Hippocampal specimens were classified neuropathologically with respect to severe segmental cell loss, gliosis, and axonal sprouting (Ammon's horn sclerosis, AHS), or the presence of a focal lesion in the adjacent temporal lobe.

Muscarinic activation reduces changes in [Ca2+]o evoked by stimulation of Schaffer collaterals during blocked synaptic transmission in rat hippocampal slices.

The rat hippocampal slice preparation and blockers of postsynaptic glutamate receptors (6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione (NBQX) 10 microM; DL-2-amino-5-phosphonovaleric acid (APV) 30 microM) were used to study the effects of muscarinic activation on stimulus-induced decreases in [Ca2+]o presumably due to presynaptic Ca-influx. Perfusion with carbachol (100-200 microM) transiently reduced these changes in [Ca2+]o. Blockade of this muscarinic effect by pirenzepine (200 microM) and prolongation of this effect after prolonged lithium (1 mM) incubation suggest involvement of the muscarinic M1 receptor subtype.

Effects of glutamate receptor agonists on presumed presynaptic Ca(2+)-signals in juvenile rat hippocampal area CA1.

The physiological role of presynaptic glutamate receptors in controlling presynaptic Ca(2+)-influx and thereby transmitter release is unknown. To test if presynaptic Ca(2+)-uptake in the hippocampus is controlled by glutamate autoreceptors, we created a hippocampal slice preparation for investigation of presumed presynaptic Ca(2+)-signals with ion-sensitive microelectrodes after lesioning of post-synaptic neurons by glucose deprivation. After prolonged glucose deprivation in slices from juvenile animals of postnatal days 13-15 and 20-22, stratum radiatum (SR) and alveus stimulation-induced postsynaptic field potential (fp) components were irreversibly abolished in area CA1, whereas SR stimulation still evoked afferent volleys.

Potassium currents in acutely isolated neurons from superficial and deep layers of the juvenile rat entorhinal cortex.

Using the whole-cell configuration of the patch-clamp technique, outward K+ currents were recorded from acutely isolated stellate cells from superficial layers, and pyramidal cells from deep layers, of the entorhinal cortex of juvenile rats. In both cell types a fast transient and a slowly inactivating outward K+ current were obtained. Whereas the fast transient current (IA) activated at potentials beyond -50 mV, the activation threshold of the slowly inactivating current (IK) was measured at -40 mV in stellate and pyramidal cells.

Modulation of A-currents by [K+]o in acutely isolated pyramidal neurones of juvenile rat entorhinal cortex and hippocampus.

Pyramidal neurones of the entorhinal cortex and of hippocampal areas CA1 and CA3 were acutely isolated from juvenile rats. The effect of lowering the concentration of extracellular potassium ions ([K+]o) on fast transient A-currents (IA) was studied using the whole-cell configuration of the patch-clamp technique. Upon lowering [K+]o from 5.

Crystals of the chemically synthesized acceptor stem of tRNAAla from Escherichia coli diffracting to high resolution.

The acceptor stem of tRNA(Ala) from E. coli has been chemically synthesized and crystallized. This duplex contains a G.

Enzymology and folding of natural and engineered bacterial beta-glucanases studied by X-ray crystallography.

1,3-1,4-beta-D-glucan 4-glucanohydrolases (beta-glucanases) are synthesized in both plants and bacteria. The enzymes specifically hydrolyze beta-1,4 glycosyl bonds that are adjacent to beta-1,3 linkages in beta-glucan, a linear polysaccharide containing these bonds in an approximate ratio of 2.5:1.

Effects of T-type, L-type, N-type, P-type, and Q-type calcium channel blockers on stimulus-induced pre- and postsynaptic calcium fluxes in rat hippocampal slices.

The contribution of T-, L-, N-, P-, and Q-type Ca2+ channels to pre- and postsynaptic Ca2+ entry during stimulus-induced high neuronal activity in area CA1 of rat hippocampal slices was investigated by measuring the effect of specific blockers on stimulus-induced decreases in extracellular Ca2+ concentration ([Ca2+]o). [Ca2+]o was measured with ion-selective electrodes in stratum radiatum (SR) and stratum pyramidale (SP), while Ca2+ entry into neurons was induced with stimulus trains (20 Hz for 10 s) alternately delivered to SR and the alveus, respectively. The [Ca2+]o decreases recorded in SR in response to SR stimulation represented mainly presynaptic Ca2+ entry (Capre), while [Ca2+]o decreases recorded in SP in response to alvear stimulation were predominantly based on postsynaptic Ca2+ entry (Capost).

Proton modulation of outward K+ currents in interferon-gamma-activated microglia.

Whole-cell outward potassium currents (IK) were measured in interferon (IFN)-gamma-activated cultured murine microglial cells. Acidification of the external milieu moved the threshold of activation of IK in a depolarizing direction, while alkalinization showed the opposite effect. A shift of more than 20 mV of the steady-state activation and inactivation curves of IK in hyperpolarizing direction was measured when pH was changed from 5.

Low Mg2+ induced epileptiform activity in the subiculum before and after disconnection from rat hippocampal and entorhinal cortex slices.

The subiculum is an area within the hippocampal complex which participates strongly in ictaform activity generated in the entorhinal cortex (EC). To study the properties of epileptiform activity with intra- and extracellular recording techniques in the subiculum, combined slices containing the EC, subiculum and hippocampus were prepared with and without surgical disconnection of the subiculum from the EC and area CA1. For induction of epileptiform activity extracellular magnesium was lowered.

Crystallization and preliminary X-ray characterization of the Methanothermus fervidus histones HMfA and HMfB.

HMfA and HMfB are histone proteins from the thermophilic archaeon Methanothermus fervidus. They wrap DNA into nucleosome-like structures and appear to represent the basic core histone fold. HMfA was crystallized in space groups P4(2)2(1)2 and P2(1)2(1)2(1).

Electrophysiological properties of neurones in cultures from postnatal rat dentate gyrus.

Electrophysiological properties of neurofilament-positive neurones in dissociated cell cultures were prepared at postnatal days 4-5 from rat dentate gyrus and studied using the whole-cell patch-clamp technique. These cells expressed a fast-inactivating, 0.5 microM tetrodotoxin-sensitive Na+ current; a high-voltage-activated (HVA) Ca2+ current, which was 30 microM Cd(2+)- and partially 2 microM nicardipine-sensitive; and an inward rectifier current, which was sensitive to extracellularly applied 1 mM Cs+.

Serotonin and 8-OH-DPAT reduce excitatory transmission in rat hippocampal area CA1 via reduction in presumed presynaptic Ca2+ entry.

The effect of 5-HT and its 1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on excitatory transmission in CA1 pyramidal cells was studied. Using concentrations of 5-HT within a range of 10-50 microM we observed no change in excitatory postsynaptic potentials (EPSPs) in CA1 cells evoked by Schaffer collateral stimulation. However, at higher concentrations, > or = 100 microM, 5-HT caused a significant decrease (30-40%) in EPSP/Cs, an effect that was also mimicked by 50 microM 8-OH-DPAT.

Effects of losigamone on synaptic potentials and spike frequency habituation in rat entorhinal cortex and hippocampal CA1 neurones.

Losigamone is an anticonvulsant both in vivo and in vitro. We here studied possible mechanisms for such effects with conventional intracellular recordings from pyramidal cells of area CA1 and entorhinal cortex in combined hippocampal-entorhinal cortex slices. Losigamone reversibly reduced the number of action potentials elicited by 1 s long depolarising current injections.

Constitutive activation of mitogen-activated protein kinase-activated protein kinase 2 by mutation of phosphorylation sites and an A-helix motif.

A recently described downstream target of mitogen-activated protein kinases (MAPKs) is the MAPK-activated protein (MAPKAP) kinase 2 which has been shown to be responsible for small heat shock protein phosphorylation. We have analyzed the mechanism of MAPKAP kinase 2 activation by MAPK phosphorylation using a recombinant MAPKAP kinase 2-fusion protein, p44MAPK and p38/40MAPK in vitro and using an epitope-tagged MAPKAP kinase 2 in heat-shocked NIH 3T3 cells. It is demonstrated that, in addition to the known phosphorylation of the threonine residue carboxyl-terminal to the catalytic domain, Thr-317, activation of MAPKAP kinase 2 in vitro and in vivo is dependent on phosphorylation of a second threonine residue, Thr-205, which is located within the catalytic domain and which is highly conserved in several protein kinases.

Comparison of voltage-dependent potassium currents in rat pyramidal neurons acutely isolated from hippocampal regions CA1 and CA3.

1. The properties of voltage-gated potassium currents were studied in acutely isolated rat hippocampal pyramidal cells from area CA1 and CA3 at postnatal ages of day 6-8, 9-14, and 26-29 (P6-8, P9-14, and P26-29) with the use of the whole cell version of the patch-clamp technique. 2.

Serotonin reduces inhibition via 5-HT1A receptors in area CA1 of rat hippocampal slices in vitro.

We studied the effects of serotonin (5-HT) on intrinsic and synaptic responses of hippocampal CA1 cells. The effects were partially mimicked by the 5-HT1A receptor agonist, 8-OH-DPAT, and prevented by the 5-HT1A receptor antagonist, NAN-190. Polysynaptic fast and slow inhibitory postsynaptic potentials (IPSPs) were reduced in amplitude by 60-70% following application of both 5-HT and 8-OH-DPAT.