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A Kuras

Publications and source records attributed to A Kuras.

7 recordsLinked to original sources
PubMed2000

Technique for producing a carbon-fibre microelectrode with the fine recording tip.

A method for making a fine carbon-fibre microelectrode is suggested here. The diameter of the recording tip of the proposed microelectrode at the borderline of glass insulation is 2-4 microm. The method uses tapering and trimming the tip of a factory-made carbon-fibre with pulsed electric current. The treated fibre is introduced into a glass micropipette of desired parameters and is fixed in it. The proposed microelectrodes have good characteristics for extracellular recording of action and synaptic potentials. The fine tip of the microelectrode can pick out a firing activity of a small single unit better and injures the nerve tissue less in comparison with the ordinary carbon-fibre microelectrode.

Action Potentials↗
PubMed1997

Multi-channel metallic electrode for threshold stimulation of frog's retina.

A simple method for making a stimulating multi-channel metallic electrode is proposed. The method uses furnace-shaped multiple fine glass tubes as channel guides for inserted tungsten wires that are pulled as a unit to produce multi-channel metallic electrode with a tapered tip. By shortening the tip, the desired inter-channels distances (from tens to hundreds of micrometers) can be established with a high degree of accuracy. Such an electrode was used to stimulate the layer of ganglion cells in a frog's retina. The responses to stimuli were recorded extracellularly in the contralateral tectum from the terminal arborizations of the excited ganglion cells' axons. A larger area of the retina may be excited when several channels are used as a cathode and several others as an anode. By varying the stimulating pairs of the channels it is possible to change the site of excitation without displacing the electrode. Separate ganglion cells may be stimulated, provided the appropriate pair of channels is selected. In this case 'all-or-none' responses to the threshold stimuli are obtained in the tectum. The artefact of the stimulus is diminished effectively by joining additional channels to the anodic one.

Animals↗
PubMed1995

Preparation of carbon-fibre microelectrode for extracellular recording of synaptic potentials.

A method is proposed for rapid and effective forming of the recording tips of carbon-fibre microelectrodes by trimming and treating the tip with electric current pulses. The tip is trimmed to the required length. The signal-to-noise ratio of carbon-fibre microelectrodes is improved at low-frequency range (less than 100 Hz) after the treatment. The same microelectrode may be used for several experiments because of the possibility to trim and treat the tips repeatedly. This method also allows one to readily fabricate 2- or multi-channel carbon-fibre microelectrodes with the vertical distance between recording tips from few tens to hundreds of micrometres. As an example, the process of fabrication of a 2-channel microelectrode is described.

Carbon↗
PubMedDate not supplied

N-cholinergic facilitation of glutamate release from an individual retinotectal fiber in frog.

Nicotinic acetylcholine receptors are localized on retinotectal axons' terminals in lower vertebrates. The effects of activation of these receptors by endogenous acetylcholine were observed under stimulation of mass optic fibers. This study was designed to determine whether endogenous acetylcholine facilitates frog retinotectal transmission, provided only the synapses of an individual optic axon are activated, and to evaluate the feasible extent of nicotinic facilitation in these synapses by applied agonist. To this end, the effects of cholinergic drugs on the extracellular action and synaptic potentials recorded from the terminal arborization of a separate retinotectal fiber (in layer F of the tectum) were investigated in vivo. Glutamatergic nature of retinotectal synapses was reexamined by treatment with kynurenic acid. Both kynurenic acid (0.25-1 mM) and d-tubocurarine chloride (10-15 microM) significantly depressed the synaptic potentials. Carbamylcholine chloride (50-150 microM) evoked a large augmentation of the synaptic potentials and a slight but statistically significant decrease of the action potentials. D-tubocurarine reduced the effect of carbamylcholine. Pilocarpine hydrochloride (50 microM) had only a weak effect. The paired-pulse facilitation of the synaptic potentials changed significantly under the action of carbamylcholine and d-tubocurarine. The obtained results suggest that the glutamate release from activated synapses of individual retinotectal axons is facilitated by endogenous acetylcholine via presynaptic nicotinic receptors. Under used stimulation conditions, this modulation mechanism was employed only partially since its activation by applied carbamylcholine could enhance synaptic transmission up to 2.8 times.

Action Potentials↗