Effect of a vasopressin analog on the chemoreactive properties of sensorimotor cortex neurons

Subcutaneous injection of 10 micrograms desglycilargininvasopressin (DG-AVP) does not alter the mean frequency of background unit activity of sensorimotor cortical neurons. However, the pattern of impulse activity is essentially changed. At the same time the reactions of sensorimotor cortical neurons to microiontophoretic administration of acetylcholine and noradrenaline experience definite changes. It is suggested that the DG-AVP-induced changes in chemoreactive properties of neurons underlie the effect of this peptide on the learning and memory.     

Effects of peripherally injected vasopressin and des-glycinamide vasopressin on the extinction of a spatial learning task in rats

An elevated eight-arm radial maze was employed to study the effects of neuropeptide administration on the spatial learning abilities of food-deprived rats. Following 18 days of reinforced training, each animal was briefly exposed to the maze with no food available in any of the eight food-cups. Immediately after this preliminary trial, animals were injected with a single subcutaneous dose of either saline, arginine vasopressin (AVP: 1.0 or 5.0 micrograms/kg), or an AVP analog with only weak endocrinological activity, des-gly-arginine vasopressin (DG-AVP: 1.0, 5.0 or 10.0 micrograms/kg). Additional extinction trials were conducted at 2, 4, 6 and 8 h post-injection. These tests consisted of individually placing an animal on the empty maze and recording the number of arms chosen in a 5-min period. In this situation, animals learn that food is no longer present in the maze and, consequently, extinguish responding. Vasopressin potentiated this radial maze extinction behavior while DG-AVP produced behavioral results directionally opposite to those predicted by a memory facilitation hypothesis. In a subsequent experiment, vasopressin had no effects on unconditioned locomotor activity measured 2 and 4 h post-injection. These results suggest that: vasopressin improved the learning that occurred during extinction of conditioned appetitive behaviors, these vasopressin effects on conditioned behavior were independent of any unconditioned, sedative or non-specific actions of the peptide, and peripheral endocrinological responses may be necessary to demonstrate memory-enhancing effects following peripherally administered AVP.     

The noradrenaline and serotonin content in symmetrical parts of the normal rat brain and during learning and peptide administration]

Content was compared of noradrenaline (NA) and serotonine (5-OT) in the right and left halves of the rats brain in norm, at elaboration of defensive conditioned reflexes of two-ways avoidance (CRTWA) and at administration of neuropeptides influencing the learning and memory--dezglycilargininvasopressin (DG-AVP), ACTH4-7 pro-gli-pro and dalargin. The conducted studies showed that in control animals the content of NA in the cortex of the right hemisphere was significantly higher than in the cortex of the left one. For the content of 5-OT in symmetric brain parts no significant differences were revealed. Under the elaboration of CRTWA the asymmetry of NA content was not eliminated. Systemic administration of DG-AVP, ACTG4-7 pro-gli-pro and dalargin practically did not change the content of 5-OT, but reduced the content of NA in the cortex and the rest of the brain, and the content of NA in the right and left cortex was equalized. The obtained data point to the asymmetric character of neuropeptides action and to greater resistance of 5-OT-ergic brain system to functional load and to administration of peptides in comparison with NA-ergic system.     

Chromatin protein metabolism and phosphorylation in the cells of different parts of the brain and liver in rats under normal conditions and under motor load

The relationship of intensive motional load with quantitative changes of the synthesis processes and phosphorylation in chromatin peptide fractions of varied polyacrylamide gel electrophoretic mobility from different rat brain structures and liver has been investigated. It has been established that the functional influences change not only the velocity of metabolism and phosphorylation but also the pattern of chromatin protein distribution. The new low molecular peptides differing in their electrophoretical mobility appear in chromatin of liver and neocortical neurons. The changes of the synthesis processes and phosphorylation typical of some fractions of the cerebral chromatin are variable and not so important as in the case of cytoplasmic proteins. The velocity of synthesis of the most proteins studied and the phosphorylation rate of some proteins increase in the neocortical neurones. The phosphorylation rate of separate low molecular peptides increases in the glial cells.     

Concentration of acid and basic proteins in the nuclei of hippocampal neurons and neuroglia of rat brain following elaboration of a passive avoidance conditioned reflex]

By means of two-wave-length visible cytophotometry, the content of acidic and basic proteins per cell nucleus was shown to increase in CA3 hippocampal neurons only 3 hours after the learning session of conditioned reflex of passive avoidance. The protein content in the nuclei of perineuronal neuroglia cells of CA3 hippocampus increased only 6 hours after the learning session. Biochemical mechanisms dealing with the process of learning are discussed.     

Relation between the impairment of creatine kinase activity and lipid peroxidation in the membranes of heart mitochondria and sarcoplasmic reticulum in experimental ischemia

Experiments were conducted on rabbits under conditions of acute restriction of coronary blood flow (intravenous injection of vasopressin in a dose of 0.5 U/kg) and preliminary administration (1 h before vasopressin) of PP-256-Na antioxidant preparation. The activity of creatine kinase isoenzymes bound with sarcoplasmic reticulum and mitochondria membranes were studied as well as the content of diene conjugates in these membranes and accumulation of malonic dialdehyde. It is shown that an essential decrease in the enzyme activity in the membranes occurs against a background of a considerable increase in the content of diene conjugates and accumulation of malonic dialdehyde. A preliminary administration of the antioxidant produces a pronounced protective effect on the enzyme activity.     

Changes in the protein level in rat hippocampal neurons during development of the alimentary conditioned reflex under normal conditions and after treatment with iproniazid

The protein content in neurons of areas CA-1 and CA-3 of the dorsal hippocampus has been determined by means of cytointerferometry in rats during elaboration of unlocal alimentary instrumental reflex (ULAIR) and local alimentary instrumental reflex (LAIR) on the background of increased and normal serotonine content in the brain. It has been found that during the ULAIR elaboration the hippocampal neurons react by an increase of dry mass, during the LAIR elaboration-by its decrease. Under condition of serotonine excess in the brain the changes of dry mass in hippocampal neurons during elaboration of the two reflexes are opposite to these observed during the ULAIR and LAIR elaboration with normal serotonine content.     

Effect of desglycine-arginine vasopressin on the excitability of the command neurons of the defensive reflex in the edible snail

Perfusion of the snail (Helix lucorum L.) CNS with DG-AVP (concentration 10(-6) M) in the course of low frequency intracellular stimulation (2-4-minute interval) of the defensive reflex command neurons led to an increase in the excitability. It was expressed both in the reduction of the spike generation latency, in the increased number of spikes in response to fixed stimuli, and in the activation of pacemaker potentials. If DG-AVP was added to the medium during endoneuronal habituation, there was no increase in the excitability. It is supposed that modification of the neuronal excitability may be caused by the DG-AVP effect on the pacemaker mechanism.     

Central cardiovascular effects of mammalian neurohypophyseal peptides in conscious rats

To confirm and extend the results of previous studies which demonstrated central cardiovascular effects of vasopressin in anesthetized rats, we determined blood pressure and heart rate changes for 30 minutes after intracerebroventricular injections of arginine vasopressin, arginine vasotocin and oxytocin in conscious rats. As compared to sham injections, significantly greater increases in either systolic or diastolic blood pressure were noted over the 30 minutes which followed the injection of 0.15, 1.0 or 10.0 nM of either vasopressin or vasotocin. In animals given vasopressin, plasma levels of the peptide were determined. There was a substantial increase in plasma vasopressin only after the highest dose. Overall blood pressure responses to doses of oxytocin as high as 100 nM were not significantly different than sham injections. Heart rate following both vasopressin and vasotocin was increased at 0.15 nM, was initially decreased then increased at 1.0 nM and was substantially decreased after the 10.0 nM dose. There was a significant increase in heart rate at the 10.0 nM and 100 nM doses of oxytocin. Dose response curves for systolic blood pressure and heart rate 20 minutes after injection were similar for vasopressin and vasotocin. We conclude that arginine vasopressin has significant central pressor and tachycardic effects in conscious rats, and it is related, at least in part, to the tail structure of the peptide, which is shared with arginine vasotocin.     

The effect of fasting and cholecystokinin stimulation on normal and neoplastic tissue in the rat pancreas.

Pancreatic nodules were produced in rats by either feeding raw soya flour alone or by injection of azaserine plus raw soya flour feeding. The resulting nodules were studied to determine whether there was any functional difference between this tissue and the relatively normal internodular pancreas. Tissue DNA and trypsin content were significantly elevated in nodules compared to the adjacent tissue. With fasting, protein and enzyme content increased significantly and equally in both nodular and internodular tissues. RNA levels fell significantly and the decrease was more pronounced in nodular tissue. The responsiveness of the multinodular pancreas to cholecystokinin was examined by measuring pancreatic secretion basally and in response to cholecystokinin. Both the volume and protein content secreted by the multinodular pancreas were greatly elevated above control levels. When corrected for pancreatic weight, the difference remained significant and appeared to be due to increased basal secretion by the nodular pancreas. These studies demonstrate that azaserine-raw soya flour induced nodules are functionally efficient. Furthermore, the secretory response to cholecystokinin of these nodules is equal to or higher than that of normal tissue.     

Effect of neurohypophyseal peptides on the formation of a conditioned feeding reflex in the rat

The influence of intraperitoneal injection of vasopressin (LVP), oxytocin (OXY) and their fragments (DGAVP, PLG) on the acquisition and extinction of conditioned food reflex was studied in rats. It was found that vasopressin and its fragments had a more pronounced specific effect on the higher nervous activity of the animals. This effect consisted in impairment of the performance of the conditioned food reflex while oxytocin had a tendency to improve its performance. On the ground of the obtained data it is suggested that administration of vasopressin may facilitate the memory function only under specific environmental conditions.     

Functional characteristics of the mature and developing brain following neuroimmunization: an analysis of the short-term plasticity of the rat hypothalamus

In experiments on mature and developing (3-4 weeks old) rats the influence was shown of neuroimmunization with summate antigens of hippocampal or neocortical tissue cytosolic fraction on short-term plasticity of hippocampal CA3 field potentials under dentate gyrus zone stimulation. An increase of paired facilitation and frequency potentiation was revealed in pyramidal layer responses of hippocampal tissue immunized animals. In case of immunization with neocortical antigens the changes were less expressed, had mainly the opposite direction and took place in the apical dendrites zone. In young animals besides antigen spectrum depending effects of neuroimmunization an earlier manifestation (in comparison with age norm) of some focal activity definitive properties was described. The suggestions are made about different localization of hippocampal or neocortical tissue immunization "targets" with possible preferential damage of intrahippocampal systems when using this structure antigens, and also about dependence of physiological consequences on the extent of target structure ontogenetic maturity.     

CHANGES IN CHROMATIN TEMPLATE ACTIVITY AND THEIR RELATIONSHIP TO DNA SYNTHESIS IN MOUSE PAROTID GLANDS STIMULATED BY ISOPROTERENOL

Chromatin template activity of mouse parotid glands increases after a single injection of isoproterenol (IPR), a procedure that causes, after a lag period of 20 hr, a marked stimulation of DNA synthesis and cell division in salivary glands of rodents. The increase in chromatin template activity occurs as early as 1 hr and peaks between 6 and 10 hr after IPR, paralleling previously reported changes in the incorporation of uridine-³H into total cellular RNA of mouse parotids. Template activity was measured in vitro in a system in which parotid gland chromatin was incubated with an exogenous RNA polymerase isolated from Escherichia coli. Similar results were obtained when template activity of parotid gland chromatin was assayed using an homologous RNA polymerase from mouse liver. Chromatin template activity in mouse parotids was also studied after the administration of drugs capable of inducing in salivary glands both DNA synthesis and secretion or secretion alone. The results indicate that the increased chromatin template activity occurring 6 hr after IPR is related to the subsequent onset of DNA synthesis. Furthermore, the increased chromatin template activity caused by IPR is inhibited by the previous administration of puromycin, an inhibitor of IPR-stimulated DNA synthesis.     

Changes in the thyrocytes to the administration of intermedin under conditions of the aminazine-altered functional state of the nervous system]

Histological and electron microscopial investigations of the thyroid gland were performed in white mice after exogeneous administration of intermedin (MSH) and intermedin against the background of aminasin. It may be concluded that while a prolonged injection of MSH results in the stimulation of the thyroid gland, the administration of the hormone in question against the background of aminasin results in the same ultramorphological structural changes of the gland which are observed after injection of aminasin alone, causing a decreased functional activity of the thyroid gland. The effect of intermedin upon the thyroid is supposed to be realized through those hypothalamus structures which are responsible for the regulation of the thyrotropic function of the hypophysis.     

Kinetics of metallo-enzymatic paramagnetic centers and free radicals in the rat liver in lung carcinogenesis

Kinetics of the content of nonheme iron-sulphur-containing (iron-sulphur) proteins, free radicals of electron-transport mitochondrial system, as well as of microsome terminal oxidase cytochrome P-450 is studied in the liver of rats at early stages of carcinogenesis and in the process of tumour growth induced by intratracheal administration of various benz(a)pyrene doses. It is found that the content of iron-sulphur proteins increases after the first administration, then it falls against a background of higher concentration of free radicals. A degree of pronounced changes in the content of the studied iron-sulphur proteins correlates with carcinogen dose. The cytochrome P-450 content is lowered for almost the whole period of carcinogen administration. In later periods animals with morphologically determinable pretumour changes exhibit a much higher content of iron-sulphur proteins, somewhat increased concentration of free radicals and a tendency to an increased level of cytochrome P-450. The appearance and growth of malignant tumours is followed by a considerable decrease in the content of iron-sulphur proteins and cytochrome P-450. On the basis of the results obtained it is supposed that the changes in the content of iron-sulphur proteins in the rat liver is the earliest and most pronounced reaction which depends on the benz(a)pyrene dose and may be of prognostic significance.     

RNA content and chromatin structure of CHO cells arrested in metaphase by colcemid

To evaluate the stability of cells arrested in metaphase, cell viability, RNA content, and chromatin structure (the latter probed by the DNA in situ sensitivity to acid-induced denaturation) were studied in uniform-age mitotic CHO cell populations maintained either at 37 degrees C (in the presence of Colcemid) or at 0-4 degrees C for up to 6 h. No significant changes in cell viability and RNA content were seen throughout the experiment for both groups of cells. The sensitivity of DNA in situ to denaturation was significantly increased during the initial 40 min of cell arrest in mitosis. However, no further chromatin changes for up to 6 h were evident regardless of whether cells were kept at 37 degrees C with Colcemid or at 0-4 degrees C in its absence. The data indicate that neither significant deterioration of metaphase cells nor progressive chromatin changes are expected during stathmokinesis experiments in vitro or during the metaphase cell arrest in cytogenetic studies lasting up to 6 h. Also, no RNA turnover can be detected in mitotic cells during this time interval.     

Peculiarities of Neurohormonal Modulation of Memory and Learning Processes in Young and Old Monkeys <Emphasis Type="Italic">Macaca mulatta</Emphasis>

Comparative data are presented about peculiarities of neurohormonal regulation of the memory and learning processes in young and old monkeys Macaca mulatta. It is shown that the hypothalamic neurohormones, vasopressin and thyroliberine, produce on the whole a unidirectional facilitating effect on the inherited and simple forms of the nervous activity in young and old animals. It is established that vasopressin, thyroliberine, and ACTH_4–10 participate differently in regulation and compensation of disturbed higher nervous functions in old monkeys. The compensatory effects of vasopressin are more pronounced at intranasal administration of its ultrasmall (0.01 jg/kg) doses. The thyroliberine administration had the longer and more expressed disinhibition effect on the conditional reflex memory in old monkeys, as compared with young ones. The question is discussed about different effects of vasopressin and thyroliberine on the higher nervous functions in young and old monkeys from the point of view of cytoarchitectonic changes in the neocortex and of immunohistochemical changes in the hypothalamus nuclear structures.     

Immunoelectron microscopic localization of estrogen receptor on pre-mRNA containing constituents of rat uterine cell nuclei

The localization and quantitative changes of estradiol receptor (ER) were studied by means of immunogold-electron microscope methods using a polyclonal antibody directed against an amino acid sequence representing the DNA binding site of ER, a monoclonal antibody against hnRNP core protein, and anti-DNA antibody. The uteri of normal rats in estrus and those of ovariectomized females were used. Ovariectomized rats were studied 21 days after surgery at different times after the injection of normal saline or estradiol-17 beta. The density of labeling was measured in interchromatin space, compact chromatin, nucleolus, cytoplasm, and background of epithelial cells, muscle cells, and fibroblasts. In the three types of cells ER was found mainly on extranucleolar ribonucleoprotein (RNP) fibrils. In epithelial and muscle cells the nucleolus was labeled but compact chromatin was not labeled. In epithelial cells there was a low but significant labeling of the cytoplasm. Fibroblasts exhibited a low labeling of the compact chromatin. Ovariectomy did not change these distributions. The estradiol injection increased labeling in all compartments of epithelial and muscle cells but decreased the labeling of compact chromatin of fibroblasts. These results show: (a) that ER is mainly nuclear but it is also present in the cytoplasm, (b) that ER binds to the nuclear particles containing newly synthesized RNA, and (c) that the binding to RNPs does not block the DNA binding domain of the ER.     

Nature of hydrocortisone-elicited amplification of template activity of liver chromatin.

The template efficiency of euchromatin region and number of RNA polymerase binding sites on this region of rat liver chromatin were significantly elevated at 3.5 h after administration of hydrocortisone to adrenalectomised rats. The euchromatin from the liver chromatin of horomone-treated rats was also found to have significantly increased levels of nonhistone proteins as compared to those in euchromatin fraction derived from adrenalectomised rats.