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D B Logunov

Publications and source records attributed to D B Logunov.

25 records · Page 2Linked to original sources
PubMedDate not supplied

[Changes in the excitability of command neurons during the initial period of conditioned reflex formation in grape snails].

The procedure of elaboration of conditioned defensive pneumostomum closure was reproduced in neurophysiological experiments on half-intact preparation of the snail. Activity of identified command neurones involved in the reinforcing unconditioned reflex, was recorded intracellularly. Conditioned and unconditioned stimuli converged on these neurones. Excitability of the explored command neurones increased during the first stages of conditioning. Appearance and consequent intensification of the initially absent spike response to the conditioned stimulus was essentially due to this excitability change. Command neurones action potentials evoked by the conditioned stimulus elicited some effector reactions which were the first signs of conditioning. The conclusion is made that the excitability changes in certain nerve cells are essential for determining the initial phase of conditioning.

Action Potentials↗
PubMedDate not supplied

[Conditioned reflex to time in grape snails].

Tactile stimulation of the snail's mantle evokes unconditioned avoidance reflex of pneumostome closure. After 3--4 experimental sessions (10 stimuli per session, a session per day) of rhythmical stimulation (interstimulus intervals 1, 2, 4 min) with some stimuli missed, the pneumostome closure occurs at the time when the missed stimulus had to be delivered, i. e. expectancy learning takes place. Arhythmical stimulation does not produce such a result. When the stimulation is stopped only two or three conditioned responses are recorded.

Animals↗
PubMedDate not supplied

[Relation between fast and slow elemental synaptic potentials in command neurons in Helix lucorum taurica L].

In experiments on a semi-intact snail preparation and a preparation of the snail isolated CNS, after spikes (Sp) evoked in presynaptic neurones by depolarizing current, not only rapid (R) EPSPs emerged in the command neurones of the defensive reaction of closing the pneumostome, but they were also followed by slow (S) EPSPs lasting over 2 min. For each single synaptic contact, the R and S EPSP amplitudes were in a good linear correspondence. In different synapses no direct connection was observed between R EPSP and S EPSP. It is suggested that R and S EPSPs may set in as a result of the action of different substances on the command neurones. Functional significance of S EPSPs with different amplitudes in different command neurones may consist in a prolonged specific preparation of the neurones for the action of stimuli.

Animals↗
PubMedDate not supplied

[Comparative analysis of the statistical parameters of synaptic transmission of central neurons in the snail Helix lucorum and in the rabbit].

Comparative analysis of the parameters of synaptic transmission in the central synapses of the snail (parietal ganglia) and in the brain of rabbit (hippocamp and sensorymotor cortex) has been made. Both differences and common features were revealed in synaptic organization of these two objects. Functional re-arrangements may alleviate differences between central synapses of the snail and rabbit. It is concluded that evolution of the central nervous system involved mainly the decrease of the effectiveness of separate synapses at the cost of the decrease of the number of quanta of the released transmitter and the increase of the number of various synaptic connections on each neuron.

Action Potentials↗