Quantitative analysis of ultrastructural changes in synapses of the rat hippocampal field CA3 in vitro in different functional states.

Transverse slices (250-350 microns) of the rat hippocampus were used for estimation of quantitative correlations between the ultrastructure and function of giant spinous synapses localized in stratum lucidum of the field CA3. Spontaneous and evoked spike discharges were used to determine the following five functional states of the neurons: "control"; "depletion" was achieved by long-term continuous stimulation (30-50 Hz for 1 h and longer); "recovery" when the slices rested after "depletion" till the evoked response was recovered; long-term potentiation I was achieved by short-term tetanic stimulation (5-15 s, 50-70 Hz); long-term potentiation II was achieved by a similar tetanic stimulation as for long-term potentiation I after the "recovery". For quantitative analysis of ultrastructural changes in the giant spinous synapses the following parameters were used: density of presynaptic vesicles determined as a ratio between the number of vesicles located within the giant bouton and the area of the latter (number of vesicles per 1 micron2); vesicle diameter distribution; area and length of the postsynaptic densities. A correlation of these parameters with the functional state of CA3 neurons was found. The area and length of postsynaptic densities are the most statistically significant parameters of the giant spinous synapses in different functional states. In contrast to other states, an increase in the length and the area of postsynaptic densities in long-term potentiation was found. A hypothesis on postsynaptic densities' role in long-term potentiation formation is suggested. The role of presynaptic and postsynaptic ultrastructural rearrangements is discussed as a possible mechanism determining the efficiency of synaptic transmission.

[Effect of interruption of afferent inputs on the background activity and nature of neuronal interconnections in the neostriatum of the cat]. / Vliianie razrusheniia afferentnykh vkhodov na fonovuiu impul'snuiu aktivnost' i kharakter vzaimosviazi neironov neostriatuma krysy.

The influence of afferent inputs disruption on distribution of various types of background activity (its mean frequency, distribution of minimal and maximal interspike intervals and character of neuronal interconnection in the neostriatum) was studied in acute experiments on rats. It was shown that the presence of grouped type of the background activity depends on the activity of the cortical input. The thalamic input makes the background activity less organized. The activity of the cortical input is also responsible for the presence of a positive symmetrical maximum in the plot of the interconnection function of neurons with a grouped type of the background activity.

[Use of surviving hippocampal slices to test drugs related to the gamma-aminobutyric acid system]. / Ispol'zovanie perezhivaiushchikh srezov gippokampa dlia ispytaniia preparatov, sviazannykh a sistemoi gamma-aminomaslianoi kisloty.

The action of gamma-aminobutyric acid (GABA) and some of its agonists and antagonists on the electrical activity of neurons from rat hippocampal slices was studied. GABA decreased the frequency of spontaneous electrical activity and raised the duration of the inhibitory period caused by electrical stimulation of the hippocampal slices. GABA agonists produced the similar action, while antagonists the contrary one. The method offered can be applied to the comparative test of GABA agonists and antagonists.

[Effectiveness of different types of reinforcement in a controlled experiment]. / Effektivnost' razlichnykh tipov podkrepleniia v upravliaemom éksperimente.

The paper shows the possibility for animals to learn to change the form of their own evoked electrical brain activity in the course of a controlled experiment. The stimulation of the brain and cutaneous pain stimuli served for rats as the reinforcing factor. The presence of two factos, functioning throughout such reinforcement, is shown: specific one, providing for the adaptive change in the evoked response, and non-specific one, always lowering the EP amplitude due to general activation. The learning is successful only in case when both factors act in one direction.

[Evoked potentials during elaboration of fine differentiations]. / Osobennosti vyzvannykh potentsialov pri vyrabotke tonkikh differentsirovok.

The paper deals with the character of changes in the EP form recorded from the visual cortex of a rat during elaboration of a system of positive and negative (with different degree of precision) conditioned defensive reflexes. It has been shown that in a state of a consolidated habit of pain stimulus avoidance in a shuttle box a negative component with peak latency up to 70 msec develops in EP to the differentiation stimulus of 0.5 c/s. This component is much less pronounced to the 2 c/s conditioned stimulus. When a more precise differentiation stimulus (1 c/s) was presented to the animal in this state the development of the studied component depended on the subsequent behavioural reaction: it developed if the animal reacted in the same way as to the differentiation stimulus. This fact suggests that the generation of this component is connected with the inhibitory processes developing at the time when the animal is choosing its behavioural reaction.

[Factorial analysis of evoked brain potentials]. / Faktornyi analiz vyzvannykh potentsialov mozga.

The method of main components aided to study the changes of EPs led from different brain structures during action of drugs on synaptic organizations of the brain. Two factors were singled out: the unspecific one comprised late components of EPs led from such structures as caudate nucleus, black substance; the specific factor united the components of EPs associated with the visual projection system and the initial component of EP in CA-1 field of the hippocampus. The weight coefficients of these two groups of components of EPs changed in different ways under the effect of drugs: the drugs different by their synaptic action exerted opposite effects upon distribution of the weight coefficients over the EP components under study.

[Adaptive changes in the evoked electrical activity of the rat brain while training it in a controlled experiment]. / Adaptivnye izmeneiia vyzvannoi élektricheskoi aktivnosti v mozge krysy pri obuchenii ee v khode upravliaemogo éksperimenta

A programmed change of a certain phase of cortical EP to a photic flash was reinforced in an unrestrained chronically operated animal (a rat) in the course of an operant controlled experiment. A painful subcutaneous stimulation or stimulation of the emotionally positive zone of the lateral hypothalamus was used as a reinforcing agent. It has been shown that painful stimulation is a more effective reinforcing agent than brain stimulation. Synchronous recordings pointed to a distinct correlation of activity in some structures (field CA1 of the hippocampus) with that of the visual cortex, while in others the EP form characteristically changed at different stages of learning (thalamic reticular nucleus), and in still others, there were no EP changes (midbrain reticular formation) at any stage of learning.