Search PubMed⌕ Search

Biomedical subjects

G G Arakelov

Publications and source records attributed to G G Arakelov.

At least 19 recordsLinked to original sources
PubMedDate not supplied

The monosynaptic connection: modulating influence of opioid peptides on the plasticity of presynaptic neurons and identified synapses.

An investigation of the effect of opioid peptides (leucine-enkephalin and methionine-enkephalin) on the plastic properties of the system of monosynaptically connected LPa7-LPa3 and RPa3, and LPa8-LPa3 and RPa3, neurons in the brain of the edible snail was carried out. It was demonstrated that all three elements in the system under investigation (the presynaptic neuron, the postsynaptic neuron, and the synapse) display the same type of plasticity, i.e., habituation to rhythmic stimulation. The enkephalins exert a modulating effect on the plastic properties of the presynaptic neuron and synapse: they slow down the habituation of the presynaptic neuron in response to intracellular stimulation and the development of habituation at a level of the synapse as well. However, the changes in the character of the postsynaptic response in the presence of enkephalins are not the direct consequence of their influence on the plastic properties of the presynaptic neuron. In addition, the enkephalins decrease the efficiency of synaptic transmission in this system: they decrease the duration of the EPSP in the postsynaptic neuron.

Animals↗
PubMedDate not supplied

Monosynaptic connection: identifiable synapses in the CNS of the edible snail.

The microanatomy of the pre- and postsynaptic neurons and the structure of the monosynaptic connection LPa7-LPa3 are described on the basis of planar reconstruction of sections of preparations of the CNS of the edible snail with neurons marked by heavy metal salts. Some physiological features of the presynaptic neuron and the monosynaptic connection were studied. The criteria for the identification of the LPa7 neuron according to its position in the ganglion, to the physiological reaction of LPa3, and to its microanatomy were determined. The position in the ganglion of three other neurons which form monosynaptic connections with LPa3 is described. The plasticity of the LPa7-LPa3 connection is demonstrated. The possibility of the realization of plasticity through the cutting off of individual synapses composing the connection is hypothesized. The results of 65 experiments on the identification of LPa7, the physiological characteristics of this cell, and its monosynaptic connection with LPa3, are summarized in this study. One preparation with a monosynaptic connection is reconstructed.

Animals↗
PubMedDate not supplied

The vision of the snail: the spectral sensitivity of the dark-adapted eye.

The spectral sensitivity of the dark-adapted eye of the snail Helix lucorum L. was investigated in semi-intact "optic cupoptic nerve-cerebral ganglion" preparations. The data of the recording of the electroretinogram in response to monochromatic radiation of varied intensities were used to plot the spectral sensitivity functions. The averaged spectral sensitivity function is well described by a Dartnall nomogram for the photopigment rhodopsin with a sensitivity peak at 496 nm.

Animals↗
PubMedDate not supplied

Mono- and polysynaptic connections between identified neurons in the system of the passive avoidance reflex of the snail.

The structure of the synaptic connections between identified sensory and giant command neurons of the parietal ganglia of the snail is examined. It is shown that the excitatory postsynaptic potential arising in the giant neuron in response to the generation of a single action potential in the presynaptic neuron consists of several monosynaptic components and may include polysynaptic components. It is hypothesized that monosynaptic components of the elementary excitatory postsynaptic potential that differ in the duration of the latent period and the dynamics of habituation may be associated with the activation of synaptic buttons on axon terminals of varying length.

Action Potentials↗
PubMedDate not supplied

[Vision in the edible snail. The morphology and total electrical activity of the retina].

Recording of the integrative electrical activity of the retina of the snail and electron microscopic study of its eye have shown the following. The electrical activity of the photoreceptors is a source of the retinogram (ERG) of the snail. ERG reaction form is characterized by two phases of a response: the initial spike and the following slow fading. For each given value of the photometric brightness of a light signal there exists a low limit of its length, beginning from which the ERG reaction of the snail assumes the form described. The value of the ERG response is a logarithmic function of brightness of the light stimulus.

Animals↗
PubMedDate not supplied

[Vision in the edible snail: the spectral sensitivity of the dark-adapted eye].

The spectral sensitivity of the dark-adapted eye of Helix lucorum L. was investigated using a semi-intact preparation "ball of the eye--optic nerve--cerebral ganglion". The amplitudes of responses of the electroretinogram to monochromatic stimuli of different intensities were used for a reconstruction of the spectral sensitivity. The averaged curve of the spectral sensitivity coincided well with the Dartnall's nomogram for a pigment having the maximum of spectral sensitivity near 496 nm.

Animals↗
PubMedDate not supplied

[The mono- and polysynaptic connections between identified neurons in the system of the passive defensive reflex in the edible snail].

A structure of synaptic connections between the identified sensory and giant command neurons of Helix lucorum was studied. It was found that EPSPs arising in the giant neuron as responses to single action potentials generation in sensory neuron consist of several monosynaptic and several polysynaptic components having different magnitude, latencies, and plasticity. The latencies of monosynaptic components are determined by different presynaptic terminals' lengths.

Animals↗
PubMedDate not supplied

[The monosynaptic connection: the modulating effect of opioid peptides on the plasticity of presynaptic neurons and identified synapses].

Study of opioid peptides (leucine-enkephalin and methionine-enkephalin) action on plastic properties of the system of monosynaptically connected neurones LPa7--LPa3, PPa3 and LPa8--LPa3, PPa3 was conducted in the snail brain. It has been shown that all three links in the system studied (presynaptic neurone, postsynaptic neurone and synapse) manifest one and the same type of plasticity--habituation to rhythmic stimulation. Enkephalins have a modulating action on plastic properties of the presynaptic neurone and synapse: they retard the habituation of the presynaptic neurone to intracellular stimulation and retard the development of habituation at synaptic level. However, changes in the character of postsynaptic response in the presence of enkephalins are not a direct consequence of their influence on plastic properties of the presynaptic neurone. Besides, enkephalines reduce the effectiveness of synaptic transmission in the given system: they reduce EPSP duration in the postsynaptic neurone.

Animals↗