Studies of the relationship between ultrastructural synaptic plasticity and ribosome number in dendritic terminals in the rat neocortex in a cellular conditioning model.

The relationship between structural changes in postsynaptic densities of axodendritic synapses and the sizes of postsynaptic ribosomal aggregations were studied. A positive correlation was found between the thickness of the postsynaptic density and the number of ribosomes. The role of dendritic mRNA and the possible mechanisms supporting rapid local protein synthesis during the modification of postsynaptic components is seen on combined administration of two neuromediators into the rat neocortex.

[The neuronal reactions of the cat motor cortex to electrical stimulation of the ventral tegmental area as a conditioned signal for the reflex of placing the forelimb on a support]. / Reaktsii neironov motornoi kory koshki na élektricheskoe razdrazhenie ventral'noi chasti pokryshki srednego mozga v kachestve uslovnogo signala dlia refleksa postanovki perednei konechnosti na oporu.

Electrical stimulation (50-100 pulses, 100-500 Hz) of the ventral tegmental area (VTA) in the vicinity of the n. interpeduncularis in the frontal plane AP2-AP4, L1-L2 caused a cat to grab food placed near its mouth. The conditioned forepaw placing reaction was elaborated using food reinforcement and VTA stimulation as a conditioned stimulus. The conditioned reflex, being once established, was repeatedly performed without extinction in the course of up to 250 trials without food reinforcement. Short (5-10 pulses) conditioned VTA stimulation evoked a prolonged (up to 1000 ms or longer) activation of neurons of the motor cortex and caused a substitution of the inhibitory phase of response to stimulation of the parietal cortex in poststimulus interval in 50-200 ms for the late secondary excitatory response.

[The effect of atropine on the ultrastructural postsynaptic plasticity of the associative type in the rat neocortex]. / Vliianie atropina na ul'trastrukturnuiu postsinapticheskuiu plastichnost' assotsiativnogo tipa v neokortekse krys.

The effect of muscarinic antagonist atropine on thickness of postsynaptic density of axodendritic synapses was studied in the sensorimotor region of the brain cortex of rats during paired repeated microapplication of glutamate and acetylcholine. In the applied conditioning paradigm atropine significantly decreased morphological dimensions of the postsynaptic density, however, the control values were not reached. This finding testifies to participation of both muscarinic and nicotinic cholinoreceptors in associative postsynaptic plasticity.

[The connection between ultrastructural synaptic plasticity and the number of ribosomes in the dendritic terminals studied in a cell model of conditioning in the rat neocortex]. / Issledovanie sviazi mezhdu ul'trastrukturnoi sinapticheskoi plastichnost'iu i chislom ribosom v dendritnykh okonchaniiakh na kletochnoi modeli obuslovlivanii v neokortekse krys.

The dependence was studied of the ultrastructural changes in postsynaptic densities of axodendritic synapses on the size of postsynaptic ribosomal aggregates. A positive correlation was established between the thickness of postsynaptic densities and the number of ribosomes. The role of dendritic mRNA is discussed and the possible mechanisms underlying rapid local protein synthesis in a modification of postsynaptic components which have been observed in case of combined application of two neurotransmitters to the neocortex of rats.

Temporal specificity in the action of stimuli during the formation of associative ultrastructural reorganizations in neurons of the cerebral cortex.

A morphometric investigation of various components of the synapses of neurons of the sensorimotor region of the cerebral cortex of rats with different variants of combined and uncombined repeated microiontophoretic application of glutamate and acetylcholine has been carried out. A substantial dependence of the character and expressivity of the reorganizations of the thickness of the postsynaptic density (PSD), of the width of the synaptic cleft, and the length of the active zone of the synapses, on the temporal relationships in the action of mediators has been identified: significant changes in the thickness of the PSD appeared only with the combined applications of the stimuli (neuromediators); the maximum thickening of the PSD was induced by the combined action of glutamate and acetylcholine with a 3-second delay in the latter. A hypothesis is presented according to which the temporal specificity in the integration of associable signals arriving at neurons is determined by the kinetics of the various interacting biochemical regulator mechanisms.

[Temporal specificity in stimulus action during the formation of associative ultrastructural restructurings in cerebral cortex neurons]. / Vremennáia spetsifichnost' v deistvii razdrazhitelei pri formirovanii assotsiativnykh ul'trastrukturnykh perestroek v neironakh kory mozga.

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]. / Izmeneniia ul'trastruktury kortikal'nykh sinapsov pri vozdeistvii assotsiirovannykh neirokhimicheskikh razdrazhitelei.

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.

[Plasticity and its physiological markers in the microsystem of cortical neurons during repeated local stimulation]. / Plastichnost' i ee fiziologicheskie markery v mikrosisteme korkovykh neironov pri mnogokratnoi lokal'noi stimuliatsii.

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.