[Ultrastructural changes in the mitochondria of Retzius' neuron exposed to hydrocortisone]. / Izmeneniia ul'trastruktury mitokhondrii neirona Retsiusa pri deistviem gidrokortizona.

The ultrastructure of the Retzius cell (gigantic neurone) mitochondria of the medical leech was investigated. After seven repeated injections of hydrocortisone into the coelomic cavity, the transformation of laminar cristae of mitochondria into tubule-vesiculated structures was discovered. A question of correlation between the structure and function independently of the systematical position of the organism is discussed.

[The role of succinic acid in neuron reaction to synaptic activation]. / Rol' iantarnoi kisloty v reaktsii neirona na sinapticheskuiu aktivatsiiu neirona.

It has been shown on Retzius neuron of the leech that after preintroduction of sodium succinate the reaction to synaptic stimulation expressed in increased frequency of the impulse activity proceeds more intensively than in the norm. In connection with the fact that against the background of succinate effect reaction to acetylcholine increases it is suggested that this very mediator is responsible for slower decrease of the impulse activity frequency at synaptic activation.

[Protective action of serotonin on changes in the ultrastructure of the Retzius neuron induced by acetylcholine]. / Protektiruiushchee deistvie serotonina na izmeneniia ul'trastruktury neirona Rettsiusa, vyzyvaemye atsetilkholinom.

A combined action of acetylcholine and serotonin is demonstrated to produce, in ultrastructure of the Retzius neuron of the leech, changes similar to those resulted from synaptic activation. Nevertheless, acetylcholine alone produces much deeper morphological shifts. A conclusion is made that serotonin not only retards impulse activity of the neuron, but it "slows down" development of rather great changes in its ultrastructure.

[Dependence of Retzius' neuron reaction to succinic acid on its initial functional state]. / Zavisimost' reaktsii neirona Retsiusa na iantarnuiu kislotu ot ego iskhodnogo funktsional'nogo sostoianiia.

It has been shown on leech Retzius neuron that the effect of succinic acid on impulse activity, respiration and redox state of flavin nucleotides depends on initial values of these parameters with the exception of membrane potential. In this case independent of its initial value the membrane potential becomes equal to 35 +/- 6 mV. The analysis of the evidence obtained has shown that the higher is the activation of cell respiration under the effect of succinic acid, the less are changes in redox-reaction of flavin nucleotides. At stronger activation of respiration the frequency of impulse activity is increased and the value of membrane potential decreased. At smaller changes of respiration the impulse activity frequency is not changed while the membrane potential increases as a rule.

[Functional restructuring of the ultrastructure of the giant neuron (Retzius') in the medicinal leech and the possible role of Ca++ ions in these processes]. / Funktsional'nye perestroiki ul'trastruktury gigantskogo neirona (Rettsiusa) meditsinskoi piiavki i vozmozhnaia rol' ionov Ca++ v étikh protsessakh.

As it has been demonstrated in the giant (Retzius') neuron of the leech (Hirudo medicinalis), at the synaptic activation for 5 sec. and 10 min., ultrastructural changes in the neuron are accompanied with an increasing number of Ca++ ions in hyaloplasm, mitochondria and cytosomes. After activation, the ultrastructural changes increase, and the number of Ca++ ions returns to the initial level. A suggestion is made on a trigger function of Ca++ ions when the neuronal ultrastructure changes under conditions of the synaptic activation.

[Bioelectrical activity and ultrastructure of medicinal leech Retzius neurons during chronic direct and synaptic activation]. / Bioélektricheskaia aktivnost' i ul'trastruktura neirona Rettsiusa meditsinskoi pilavki pri dlitel'noi priamoi i sinapticheskoi aktivatsii.

The threshold direct or synaptic 1/sec stimulation of the Retzius cells increases the firing rate of the neuron in the leach. The firing rate becomes synchronized with the stimulation applied. The membrane potential does not change. After 10 min of such stimulation changes occurring in the ultrastructure of neuron are similar to those in a neuron with no stimulation: these changes reveal a decrease in the synthetic processes whereas the bioelectrical activity remains the same which suggests a certain independence of the neuron electrophysiological parameters of its ultrastructure.

[Characteristics of synaptic and intracellular neuron activation]. / Spetsifika sinapticheskoi i vnutrikletochnoi aktivatsii neirona.

Stimulation of the leech abdominal neural chain with electric pulses of 1 imp/sec frequency results in alterations in the activity of the Retzius cells in addition to an increased protein metabolism in the postactivation period. The direct stimulation produces a decrease in the cellular protein metabolism.

[Strength of synaptic stimulation and morpho-functional reorganization of the neuron].

In the Retzius cell of the leech, synaptic threshold and three-fold threshold stimulation 1/sec was followed by readjustment of the cell spike activity according to the stimulation rhythm. After cessation of the stimulation the initial bioelectrical activity restores. The membrane potential remains unaltered during the three-fold threshold stimulation. Electron-microscopically, the Retzius cells develop different ultrastructural changes. In case of the threshold stimulationthe changes indicate an intensification of the synthetic processes and, on the contrary, the three-fold threshold stimulation is followed by a decrease in the proteinmetabolism. In the first case, the amount of granular endoplasmatic reticulum increases and in the second case -- decreases. The same is true for the total amount of ribosomes. During synaptic stimulation, the Retzius cell mitochondria remain unlatered while during the three-fold threshold stimulation the mitochondria swell, their matrix clears up, and their krysts become reduced.