No abstract

Long-term potentiation was elicited in living slices of rat olfactory cortex by stimulation of the lateral olfactory tract. A group of interdependent parameters of membrane metabolism was studied, i.e., the kinetics of 45Ca metabolism, lipid peroxidation, and antioxidant defense; cytochemical measurements were made of Na+, K(+)-ATPase activity in neurons and glial cells; the functional (GTPase) activity of G-proteins was also studied. All parameters were compared with the bioelectrical activity of slices at three time points after tetanization, i.e., 3-5, 15, and 30 min. In most cases, regular phasic changes in metabolic parameters occurred, and their functional significance is discussed.

Existing data on the role of Ca2+ ions in the development of long-term potentiation were used as a basis for studying changes in different Ca2+ compartments in cells in living rat olfactory cortex slices during potentiation. The kinetics of 45Ca2+ exchange were studied at 5, 15, and 30 min of potentiation. During the induction phase (1-5 min) of long-term potentiation, the fraction of tightly-bound intracellular Ca2+ decreased. There were no changes in the content of Ca2+ ions in other fractions at this stage. During maintenance of potentiation, which lasted 15-25 min, Ca2+ levels in the extracellular and intracellular compartments did not differ from controls. At 30 min, during extinction of long-term potentiation, there was a significant redistribution of Ca2+ in cells: the levels of free and loosely-bound Ca increased, as did extracellular Ca2+.

A studied has been carried out, in investigations of the biochemical mechanisms of memory --in particular of the learning process --of the shifts in the metabolism in the central nervous system in the brain or its divisions. These investigations have been directed first and foremost to the study of the macromolecular components of the cells of the nervous system, proteins and nucleic acids. The data obtained indicate that learning is based on change in the composition of RNA of the nuclei of neurons and glial cells of neural structures which leads to the biosynthesis of new, specific proteins [11]. It has been demonstrated that the metabolism of RNA and proteins in nerve ceils may in fact have great significance for the unfolding of some stages of the establishment of memory [1,5,10]. It can be hypothesized that the neurochemical reaction of the ceils of a surviving slice to posttetanic potentiation as a model of positive learning [4] will touch upon the metabolism of RNA and proteins in them. The quantitative shifts in the content of the substances in particular neurons and in satellite glial cells under the conditions of various functional activities make it possible to take the method of demonstrating them histochemically into account. This method can define not only quantitative shifts, but some morphological characteristics of the cells during posttetanic potentiation as well.The aim of the study was the determination of the total protein content and the content of SH-groups of proteins and RNA in neurons and glial cells of the olfactory region of the cortex of surviving brain slices.The experiments were carried out in male Wistar rats, weighing 180-200 g. Ten animals were used in the experiLaboratory of Functional Neurocherr~stry, I. P. Pavlov Instit~Ite of Physiology, Russian Academy of Sciences, Saint Petersburg.ments. Tangential slices of the olfactory region of the cortex, 400-500 l~m in thickness, were prepared by means of a special cutter; the incubation and posttetanic potentiation were carried out in the manner described previously [4].In order to determine the number of macromolecules in the cells, the slices were fixed following incubation in Brodskii's mixture: 10% formalin--alcohol--acetic acid in a 3:1:0.3 ratio for 30 min; they were then passed through absolute alcohols and alcohol--chloroform mixtures in the conventional protocol, and mounted in paraffin [2]. Frontal paraffin slices, 6-8 l~m in thickness, were made up on a microtome. Twenty neurons and glial cells apiece were examined in the slices from each animal. The concentration of the proteins, the SH-groups of proteins [7], and RNA [8] was determined in an MtsF-VI microscope photometer on the basis of the optical density of the staining [6] in the cytoplasm of the pyramidal neurons and the bodies of glial cells of the olfactory cortex. The content per cell was established by multiplying the results of the concentration of the substances and the volume of the cells, calculated on the basis of the linear dimensions [6]. The significance ...