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Biomedical subjects

G N Akoev

Publications and source records attributed to G N Akoev.

At least 73 records · Page 4Linked to original sources
PubMed1987

[Effects of aspartic acid in the electroreceptors of the skate].

To identify the afferent transmitter in ampullary electroreceptors of the marine skates effects of L-aspartic acid (L-ASP) were examined using bath application of the drug. Perfusion of the basal membrane with L-ASP produced an increase in activity in most experiments (threshold concentrations 10(-7) M). L-GLU and L-ASP were identical in their ability to activate the afferents. In the presence of presynaptic blockade (high Mg2+) bath application of L-ASP restored the resting activity, suggesting a postsynaptic action of L-ASP. The results are consistent with the view that L-GLU, L-ASP or a related compound may play a role in afferent transmission in the ampullae of Lorenzini of skates.

Action Potentials↗
PubMed1987

[Analysis of the effect of glutamic acid diethyl ester on synaptic processes in the ampullae of Lorenzini of the skate].

The effects of glutamic acid diethylester (GDEE) on the electrical activity of the ampullae of Lorenzini were studied in skates. GDEE (10(-6)-10(-4) M) caused a decrease in frequency of afferent discharges in all receptors under study. GDEE also reversibly blocked the effects of excitatory amino acids (L-glutamate and L-aspartate). The results suggest that L-glutamate or related substance is likely to be the synaptic transmitter in the ampullae of Lorenzini.

Animals↗
PubMed1987

[Brain neurite-stimulating protein].

A protein possessing the neurite-stimulating activity in organotypic cultures of chicken embryo spinal ganglia was isolated and purified from bovine brain tissue. The isolation and purification procedures included acid extraction, ultrafiltration, preparative polyacrylamide gel electrophoresis and chromatography on heparin-Sepharose. The molecular weight of the protein is about 15000 Da. The neurite-stimulating activity of the purified protein manifests itself at a protein concentration of about 10(-9) M.

Animals↗
PubMed1986

[Effect of kainic acid on synaptic transmission in the electroreceptors (ampullae of Lorenzini) of the skate].

Superfusion of the basal membrane of the ampullae of Lorenzini of the skate Raja clavata with 10(-6)-10(-9) M kainic acid produced significant and reversible changes in background firing rate depending on its initial level. When synaptic transmission was abolished by high Mg2+ solution, succeeding superfusion with kainic acid and Mg2+ containing solution restored the background and evoked activity in the afferent fibres. It is suggested that the observed effects of kainic acid on the activity of the ampullae of Lorenzini may be explained mainly by its presynaptic action.

Action Potentials↗
PubMed1986

[Morphofunctional restoration of a nerve trunk by filling the defect with a blood vessel].

Dynamics of morphologic and functional restoration of the nerve trunk and separate receptive skin formations have been investigated in white rats after a sutureless connection of the cut nerve by means of the implanted artery. For testing the reparative processes neurohistological and electrophysiological techniques have been used. In spite of a relatively early restoration of the integrity of the injured nerve and reaching the nervous fibers up to the skin, functional organization of the dermal sensory apparatus is observed only in a year after the operation.

Animals↗
PubMed1985

[Effect of gamma-aminobutyric acid, taurine and catecholamines on the synaptic processes in Lorenzini's ampules in Black Sea skates].

Perfusion of the basal membrane of the ampullae of Lorenzini with GABA, taurine or catecholamines produced a reversible decrease in resting and evoked activity in afferent nerve fibers. Picrotoxine, phentolamine and propranolol did not suppress the electrical activity. Our findings exclude GABA, taurine and catecholamines as the transmitters at the ampullary electro-receptorsensory nerve synapses.

Afferent Pathways↗
PubMed1984

Physiological properties of lateral line receptors of the lamprey.

Single unit recording from the lateral line nerve of the lamprey revealed the existence of two types of afferents. One type reacts to electric fields (threshold 10-30 microV/cm) and is insensitive to weak mechanical stimuli. The other type is very sensitive to water displacement and does not respond to weak electric fields. The properties of the electroreceptors of the lamprey are discussed and compared with other types of electroreceptors.

Animals↗
PubMed1984

Effects of potassium ions on the impulse activity of the ampullae of Lorenzini of the skate.

Perfusion of the basal membrane of the ampullae of Lorenzini with high potassium solution caused a substantial increase in the resting firing rate. This effect was not accompanied by any change in the threshold of the afferent fibres. The low potassium solution caused a decrease in the resting firing rate. When synaptic transmission was abolished by high Mg2+ solution, succeeding perfusion with 10 mM K+ did not induce responses in the afferent fibres. The role of potassium ions in the activity of the ampullae of Lorenzini is discussed.

Animals↗
PubMed1984

[Effect of glutamic and aspartic amino acids on the electrical activity of the ampullae of Lorenzini in skates].

Perfusion of the basal membrane of the Lorenzini ampullae with 10(-4)-10(-6) M L-glutamic amino-acid, irrespective of the concentration of the amino-acid, produced reversible changes in resting firing rate depending only on initial resting rate. D-glutamic and L-aspartic acids exerted inhibitory effects of the electrical activity. The findings are consistent with the opinion that L-glutamic acid is the synaptic transmitter in the Lorenzini ampullae.

Animals↗
PubMed1984

[Effect of potassium ions on the electrical activity of ampullae of Lorenzini in the skate].

Effect of different concentration of externally applied K+ on the resting and evoked discharge of the isolated Lorenzini ampullae was studied in skates. It was shown that low K+ or K+-free solutions caused a decrease in the frequency of the afferent discharge. An increase in K+ concentration (6-10 mM) produced a reversible increase in the resting activity, with no effect on the receptor thresholds to electrical stimulation. When synaptic transmission was abolished by Mg+2 (30-40 mM) an increase in K+ concentration induced no activity in the afferent nerve discharge. However if L-glutamate was added to the Mg+2-containing solution, it partially restored the activity and addition of K+ caused an additional increase in the existing activity.

Action Potentials↗
PubMed1983

Effects of acetylcholine and cholinolytics on the synaptic transmission in the ampullae of Lorenzini of the skate.

1. The effects of ACh, D-tubocuraine and atropine on the electrical activity of the ampullae of Lorenzini of the skate were studied. 2. ACh (10(-5)M) caused an increase in frequency of afferent discharges in all receptors under study. 3. When excitability was abolished by high Mg2+ solution (50 mM) perfusion with 50 mM Mg2+ plus ACh did not induce firing in the afferent fibres. 4. Cholinergic antagonists (D-tub and atr) did not block the synaptic transmission. 5. The results suggest that ACh is unlikely to be the synaptic transmitter in the ampullae of Lorenzini.

Acetylcholine↗
PubMed1983

[Predominant blocking of fast potassium current channels in mollusk neurons by 4-aminopyridine].

Blocking effects of 4-aminopyridine (4-AP) on ionic currents were studied in Lymnaea stagnalies neurones using the suction pipette method for voltage clamp and internal perfusion. When applied externally, 4-AP blocks transient potassium current as well as early inward and delayed outward currents, apparent dissociation constants being 0.4 mM (E = -40-- -30 mV); 6.5 mM (E = -10-- -20 mV); 24 mM (E = 20 mV), resp. Intracellular 4-AP changes the constants to 0.85, 77, 55 mM. An experimental study of a possible role of the transient potassium channels in the regulation of molluscan unit activity seems to be effective when 4-AP is applied internally as it blocks then the transient potassium channels in a selective manner.

4-Aminopyridine↗
PubMed1982

The effect of Mg2+ and Ca2+ on the excitability of Pacinian corpuscles.

The effect of altering extracellular Ca2+ and Mg2+ levels on electrical properties of Pacinian corpuscles of adult cat has been examined. High Mg2+ solution (5--15 mM) increased the excitability of the receptors and the amplitude of the receptor potential. Ca2+-free EDTA solution caused an increase in the amplitude of the receptor potential in the first 60 min and then its decrease. Mg2+ ions slow down or prevent the depressant effect of the Ca2+ lack on the receptor potential. The phase of the receptor potential amplitude increase in Ca2+-free media was reversibly blocked by tetraethylammonium ions. Treatment with 2,4-dinitrophenol produced a transient increase in the receptor potential amplitude. The threshold of the mechanosensitive receptor membrane was unaffected in Ca2+-free or Mg2+-rich solution. The results suggest that divalent cations are not directly involved in the process of mechanoelectric transformation in Pacinian corpuscles.

Animals↗