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O A Maksimova

Publications and source records attributed to O A Maksimova.

At least 19 recordsLinked to original sources
PubMed2001

A single serotonergic modulatory cell can mediate reinforcement in the withdrawal network of the terrestrial snail.

A cluster of 40 serotonergic cells in the rostral part of pedal ganglia of the terrestrial snail Helix lucorum was shown previously to participate in the modulation of withdrawal behavior and to be necessary during the acquisition of aversive withdrawal conditioning in intact snails. Local extracellular stimulation of the serotonergic cells paired with a test stimulus elicited a pairing-specific increase (the difference between paired and explicitly unpaired sessions was significant, p <.01) of synaptic responses to test stimulation in the premotor interneurons involved in withdrawal. This result suggested participation of serotonergic cells in mediating the reinforcement in the withdrawal network. Intracellular stimulation of only one identified Pd4 cell from the pedal group of serotonergic neurons paired with a test stimulus also significantly increased (the difference between paired and explicitly unpaired sessions was significant, p <.05) synaptic responses to paired nerve stimulation in same premotor interneurons involved in withdrawal. Morphological investigation of a cluster of pedal serotonergic neurons showed that only the Pd4 cell had branches in the parietal ganglia neuropile where the synapses of premotor withdrawal interneurons and of presynaptic neurons are located. The data suggest that a single serotonergic cell can mediate the reinforcement in the withdrawal network of the terrestrial snail. Patterns of responses of the Pd4 cells to tactile and chemical stimuli conform to the suggestion.

Animals↗
PubMed1993

Positive and negative brain zones in the snail.

Fine wire electrodes were surgically implanted in two regions of the brain of the snail Helix aspersa. To receive electrical stimulation of the brain, a tethered snail was required to displace the end of a rod. Self-stimulation delivered to the parietal ganglion resulted in non-repetition of the operant response, whereas self-stimulation delivered to the mesocerebrum resulted in an increase in response frequency. The reinforcing effect of local extracellular stimulation of two brain zones was investigated in a semi-intact preparation of a closely related species with an identical cellular map (H. lucorum). It was found that mesocerebral stimulation increased the frequency of the reinforced spontaneous movement, but decreased the frequency of the same movement if its absence was reinforced. These results allow us to attribute positive reinforcing effects to this brain area, which is involved in the control of sexual behaviour. Different results were obtained by contingent stimulation of the rostral part of the parietal ganglia, where giant cells controlling avoidance behaviour are located. Stimulation of this zone resulted in a decrease in the frequency of the ongoing spontaneous movements. These findings make possible intracellular investigations of the mechanisms of positive and negative reinforcement.

Animals↗
PubMed1986

[Role of serotonin in the development of the defensive reflex to food in the snail].

9-16 days after injection of 5,7-dihydroxytryptamine which elicits degeneration of serotonergic nerve cell terminals, pairing of food and electrical shock had no effect on responses of injected animals to food, while definite food-aversive reactions were observed in control animals. In neurophysiological experiments applications of serotonin in the chamber containing the nervous system was used as a reinforcing stimulus. The amplitude of synaptic responses to nerve stimulation increased significantly in preparations in which stimulation was paired with serotonin application. In neurons involved in defensive reactions after 3-7 pairings of a drop of juice to the chemoreceptive part of the skin with serotonin application a new spike response to food has appeared. Unpaired presentations of the same stimuli were not effective. It is concluded that serotonin is an important factor in formation of conditioned adverse reactions in the snail.

Animals↗
PubMedDate not supplied

Reinforcing effect of stimulation of the mesocerebral region of the brain of the edible snail.

Two regions of the brain of the edible snail were stimulated. The spontaneous movements, either opening or closing, of the opening of the mantle cavity served as the signal for the stimulation. The stimulation of the region of the mesocerebrum of the edible snail in a semi-intact preparation may serve as a positive reinforcement of intercurrent behavior, while stimulation of the rostral portion of the parietal ganglia may serve as a negative reinforcement. Depending upon whether the movement itself or its absence is reinforced, the change in the intercurrent behavior may change sign.

Animals↗
PubMedDate not supplied

Behavioral plasticity in a snail and its neural mechanisms.

This paper reviews the behavioral and neural mechanisms of habituation, sensitization, environmental condition, and food-aversion conditioning in the snail helix. The possible participation of motivational systems and changes in plasticity during development are discussed.

Animals↗
PubMedDate not supplied

Suppression of synaptic input of defense behavior command neurons by stimulation of neurons of the mesocerebrum in a preparation of the isolated CNS of the common snail.

The intestinal nerve was stimulated in combination and uncombined with extracellular stimulation of the mesocerebral region of the brain, as well as with stimulation of serotoninergic neurons, in experiments on a preparation of the isolated CNS of the common snail, with preservation of the nerve connections with the sexual system. Responses were recorded in command neurons of defense behavior. The data were obtained indicating that, in the case of combinations with extracellular stimulation of the mesocerebrum, an analog of a conditioned reaction of diminution of EPSP in the command neurons of defense behavior was developed. When stimulation of the same nerve was reinforced by stimulation of the serotoninergic neurons, sensitization appears, both in the case of combined and uncombined presentation of the stimuli.

Action Potentials↗
PubMedDate not supplied

Two modulatory inputs exert reciprocal reinforcing effects on synaptic input of premotor interneurons for withdrawal in terrestrial snails.

A cluster of serotonergic cells in the rostral part of pedal ganglia of the terrestrial snail Helix lucorum was shown previously to participate in modulation of withdrawal behavior, and to be necessary for elaboration of aversive withdrawal conditioning in intact snails. In the present experiments local extracellular stimulation of the serotonergic cells elicited a pairing-specific increase (difference between paired and explicitly unpaired sessions was significant, P<0.01) of synaptic responses in the premotor interneurons involved in withdrawal to paired nerve stimulation. Intracellular stimulation of only one Pd4 cell from the pedal group of serotonergic neurons increased (P<0.05) synaptic responses to contingent test nerve stimulation significantly in the same premotor interneurons for 2-3 hr. Mesocerebral cells are known to participate in male sexual behavior, and their extracellular stimulation was shown previously to suppress the amplitude of synaptic responses in withdrawal interneurons. Local extracellular stimulation of the mesocerebral cells elicited a pairing-specific decrease (P<0.01) of synaptic responses to contingent test nerve stimulation in the premotor interneurons involved in withdrawal for 2-3 hr. Paired application of met-enkephaline (10(-6) M, some mesocerebral cells are enkephaline-like immunoreactive) also selectively decreased synaptic responses to contingent nerve stimulation in the premotor interneurons for hours. Thus, two modulatory inputs exert pairing-specific effects that influence the same synaptic connection in opposite directions, which may underlie the long-term up- and down-regulation of behavioral responses.

Animals↗
PubMedDate not supplied

[Comparative evaluation of neurovirulence of domestic and foreign live mumps vaccine].

Morphological and immunofluorescent study of changes in the central nervous system of monkeys with mumps was carried out in order to determine the criteria of neurovirulence of different mumps virus strains. Quantitative evaluation showed a lower residual neurovirulence of L-3 strain vs. Jeryl Lynn and Urabe Am9 strains. Use of new methodological approaches to evaluation of mumps vaccine strain neurovirulence will improve the safety control of live mumps vaccines.

Animals↗
PubMedDate not supplied

[The behavioral plasticity of the edible snail and its neuronal mechanisms].

Published results concerning behavioural habituation, sensitization, long-term processes, environmental conditioning, and conditioned food aversion in terrestrial snail Helix are discussed. Neural mechanisms underlying behavioural changes are considered. Problems of participation of motivational processed and development of plasticity in ontogenesis are reviewed.

Animals↗
PubMedDate not supplied

[The reinforcing action of stimulation of the mesocerebral area of the brain in the edible snail].

Reinforcing effect of extracellular stimulation of two brain zones on spontaneous opening of pneumostome was investigated in semi-intact preparation of the snail. It was found that mesocerebrum stimulation increased the frequency of the reinforced movement, but decreased the frequency of the same movement it its absence was reinforced. These results suggest positive reinforcing effect for this brain area involved in control of sexual behaviour. Different results were obtained for stimulation of rostral part of parietal ganglia where giant cells controlling avoidance behaviour are located. Stimulation of this area decreased the frequency of the ongoing spontaneous movements. Implications for the control of behaviour are considered.

Animals↗
PubMedDate not supplied

[Cellular reactions to elaboration of a backward conditioned connection in Helix lucorum].

After 10-15 food stimuli paired with electrical shock in semi-intact snail preparation, responses to strong tactile stimuli identified feeding behaviour neurones were studied. Inhibition evoked by tactile stimulation in these cells before learning procedure disappeared and in some cases noxious stimulus evoked synaptic activation corresponding to feeding reactions in the intact animal. Changes in second-order sensory neurones pre-synaptic to the command neurones of avoidance behaviour are suggested to be the mechanism of forward conditioned connection as well as the mechanism of backward conditioned connection.

Animals↗
PubMedDate not supplied

[Differences in the responses of identified neurons to chemical stimuli in satiated and hungry edible snails].

Reactions of command neurones for avoidance behaviour to food were investigated in hungry and satiated snails in "CNS-chemoreceptor" preparations, in which hemolymph was washed out by saline. Neuronal responses in hungry animal preparations differed significantly from responses in satiated animals preparations. Perfusion of hungry animal preparations with hemolymph of satiated animals changed significantly the responses of command neurones for avoidance behaviour. These responses resembled the reactions of the same neurones to food after aversive conditioning to food of hungry snails. The role of humoral factor in learning is discussed.

Animals↗