[Arachidonic acid and its acyclic derivatives regulate the short-term plasticity of the cholinoreceptors of the neurons in the edible snail].

On identified Helix neurones RPa3 and LPa3 using the method of double-electrode clamp technique on the membrane the influence was shown of eicosanoids on the dynamics of inward current extinction caused by the repeated ionophoretic applications of acetylcholine to soma. Extracellular influence of arachidonic acid (50-100 microM) increased the extinction. Phospholipase A2 inhibitor quinacrine hydrochloride (100-600 microM) decreasing the content of arachidonic acid in the cell acted differently.

[Calmodulin blockaders weaken the short-term plasticity of the neuronal cholinoreceptors in the edible snail].

By means of recording transmembrane ion currents of identified snail neurones PPa3 and LPa3 a reversible weakening was shown of the speed and depth of extinction of neuronal cholinoreceptor membrane reactions to repeated iontophoretic applications of acetylcholine to the soma by a number of calmodulin blockaders: R24571 (20-50 mmol/l), trifluoperazine (50-200 mmol/l), chlorpromazine (20-60 mmol/l) and prenylamine lactate (30-400 mmol/l). The obtained results testify to a positive control by calmodulin of short-term cholinoreceptors plasticity of the studied neurons.

[The negative shift in the reversal potential of the acetylcholine-induced incoming current in the RPa3 and LPa3 neurons of the edible snail during its extinction].

A negative shift of reversal potential at its extinction has been found with the current-voltage relation of acetylcholine-induced inward current in Helix lucorum's RPa3 and LPa3 neurons. An assumption has been made on a nonuniform extinction of acetylcholine-induced currents which is due to the motion of different ions. Ion flow with a more positive equilibrium potential decreases to a greater degree than reversal potential.

[Calcium regulation of the short-term plasticity of the cholinoreceptors in neurons RPa3 and LPa3 of the edible snail].

Pharmacological influences, changing intracellular content of Ca2+, reversibly change the speed and depth of extinction of the input current of the Helix RPa3 and LPa3 neurones, elicited by a repeated iontophoretic application of acetylcholine to the soma. Suppression by extracellular medium, devoid of Ca2+ and by verapamyl (100-150 mumol/l) of Ca2+ input to the cell, induced by cholinoreceptors activation, reversibly weakens the extinction. Raise of intracellular Ca2+ level by blockade with ruthenium red (5-10 mumol/l) of specific Ca2+ transport by mitochondria and by mobilization with caffeine (1-4 mmol/l) of Ca2+, deposited by endoplasmic reticulum, accelerates and intensifies the extinction.

[The role of cGMP in extinguishing the reactions of identified neurons in the edible snail to acetylcholine].

Possible role of cGMP is studied in control of extinction of snail neurones RPa4, RPa3 and LPa3 reactions to acetylcholine (ACh), applied rhythmically to neurone soma by means of microiontophoresis. It is shown that guanylate cyclase activators which raise the cGMP level in the cell--Na nitroprusside and Na azide (5,10(-4)-10(-3) mol/l)--intensify at extracellular application the extinction of inward transmembrane current and membrane depolarization in response to ACh. Suggestion is made about participation of cGMP-dependent phosphorylation of membrane proteins in control of the development rate, depth and duration of neurone cholinoreceptors short-term plasticity.

[Temporal specificity in stimulus action during the formation of associative ultrastructural restructurings in cerebral cortex neurons].

By a method of electronic microscopy morphological characteristics were studied of various components of neurones synapses in the sensorimotor cortical zone of rats at different variants of combined and noncombined repeated microiontophoretic presentation of glutamate and acetylcholine. Significant dependence was found of the character and rate of reorganizations of postsynaptic thickness (PSTh), width of synaptic cleft and length of synapses active zone on temporal relations in transmitters action: significant changes of PSTh thickness appeared only in conditions of combined presentations of stimuli (neurotransmitters); maximum thickening of PsTh was caused by the combined action of glutamate and acetylcholine with 3 s delay of the latter. The hypothesis is suggested that temporal specificity during integration of associated signals action to neurones is determined by kinetics of interacting biochemical regulating mechanisms.

[Changes in the ultrastructure of cortical synapses during exposure to associated neurochemical stimuli].

Dependence of changes in the postsynaptic density, active zone and synaptic cleft on time relations between the administered associated stimuli was established. Locally applied glutamate and acetylcholine were used as the stimuli.

[Protein kinase C is not involved in regulating the short-term cholinoreceptor plasticity of the PPa3 and LPa3 neurons of the edible snail].

A voltage clamp technique on identified Helix lucorum's RPa3 and LPa3 neurons has been used to negate the effect of protein kinase C on extinction of response to repeated iontophoretic applications of acetylcholine to soma. Extracellular influence of phorbol ether, protein kinase C activator (12-O-tetradecanoylphorbol-13-acetate, 0.1-10 mumol/l), or polymyxin B, its blocker (100-500 mumol/l), do not affect the extinction of acetylcholine-induced neuronal response.

[Second messengers in the regulation of nerve cell plasticity during learning].

A review of 1972 to 1988 publications is presented, as well the data obtained by the authors on the influence of second messengers and their intracellular receptors on neuron plasticity in the learning experimental models. The emphasis is laid on cyclic 3',5'-adenosine monophosphate; cyclic 3',5'-guanosine monophosphate, calcium ions and their intracellular receptor calmodulin, as well as on the metabolites of phosphoinositide exchange: inositol-1, 4, 5-trisphosphate, 1,2-diacylglycerol and protein kinase C activated by the latter and arachidonic acid.

[An experimental approach to research on the integrative properties of a single brain neuron].

The difficulties in investigation of the single neuron integrative properties in mammalian brain are connected with the absence of a mean of determination of neuronal set contribution in their activity. In given paper an experimental approach to the decision of this task is proposed. It consists in neuron activity investigation in the model learning training situation under condition of partial functional isolation from nervous cells by means of decrease in extracellular calcium concentration level using ethylene glycol tetraacetate.

[The significance of multiple neuromediator activity in supporting integrative brain functions].

Properties were studied of reactions of neural cells of the sensorimotor cortical area to locally microionophoretically administered l-glutamate, acetylcholine, norepinephrine and gamma-aminobutyric acid. It is shown that neuronal reactions to the action of the above-mentioned transmitters differ both in direction of change in the impulse activity frequency and in temporal offracteristics (latency and duration of after-effect). It is substantiated that due to the specificity of temporal ranges of action of the transmitter on neural cells, the possibility of effective interaction and temporal coding of heterofunctional information is provided.

[Learning and memory: neurophysiological mechanisms].

The analytical review of study of neurophysiological basis in different kinds of learning and memory in animal and human is given. The main attention is paid to the consideration of systemic and neuronal levels of habituation and conditioned reflexes. A conception on the brain functional state as the main mechanisms of learning and distributed multicomponent engram corresponding to the integrative process peculiarities is developed.

[Integrative properties of the microsystem of cortical neurons during repeated local stimulation].

Small groups of neighbouring neurons in neocortex are able to form separate microsystem in model situation of habituation during the local repetitive action of acetylcholine. This new functional unit exhibits a number of main properties which are characteristic of systemic processes of habituation. Only some of the properties don't reproduce in microsystem of cortical neurons.

[Plasticity and its physiological markers in the microsystem of cortical neurons during repeated local stimulation].

Separate neuronal microsystems in the sensomotor cerebral cortex are able to exhibit the functional plasticity under conditions of repeated action of acetylcholine applied microiontophoretically. The characteristic properties of dynamics in activity of single cortex neurones are determined mainly by the initial reactivity to transmitter and by the state of nervous cells of the surrounding microsystem. The composition and succession of response components as well the duration of excitatory stage of reaction to acetylcholine serve as physiological markers of plastic properties of neurones in cortical microsystem.

[The role of cyclic 3',5'-adenosine monophosphate in the extinction of the reaction of identified neurons in the edible snail to acetylcholine].

The recording of transmembrane currents and intracellular potentials has been used to show on Helix lucorum identified neurons RPa4, RPa3 and LPa3, that pharmacologic effects on adenylate cyclase system do not influence the extinction of neuronal response to repeated local iontophoretic applications of acetylcholine to the soma. Neither cAMP-raising adenylate cyclase activator forskolin (2-6 x 10(-5) mol/l), nor cAMP-lowering phosphodiesterase activator imidazole (5 x 10(-3) mol/l) alter the dynamics of extinction of response to acetylcholine. A conclusion has been made that shortterm plasticity of cholinoreceptors in the investigated neurons is independent of intracellular cAMP level.

[Evaluation of forms of cortical neuron response to acetylcholine].

Analysis was carried out of the form of excitatory components of the reaction of 92 neurones in rats sensorimotor cortical area to electrophoretically applied acetylcholine. The used method of approximation of neuronal reaction form by two polynomes of the second degree allowed to identify one- and two-component types of responses to the transmitter. It is suggested that in genesis of the excitatory component of neuronal reaction to acetylcholine one or two types of cholinoreceptors may participate.

[Reactions of neurons in the sensory-motor cortex on different amounts of administered acetylcholine].

As a result of acetylcholine iontophoresis with different currents 3-fold increase of transmitter compared with the threshold one for reaction has been shown not to result in change of a type of reaction pattern more than in 80.3% of neurones. Such increase of action force is quite enough for the significant lengthening of the reaction excitatory components in the most of investigated neurones.