Newly revealed range of action in the preparation derinat: Mnemotropic effect

Mnemotropic effect has been revealed in the action of Derinat, a biologically active compound of natural origin, on the formation of conditioned reflexes of active and passive avoidance. Derinat accelerates the elaboration of conditioned reflexes. This effect manifests itself already at initial stages of the elaboration, which resembles the effect produced by nootropics.     

Evaluation of the effect of arginine vasopressin on the formation of the conditioned reaction of active avoidance in rats

The effect was studied of arginine-vasopressin (AVP) intraperitoneal administration in a doze of 0.001 mg/kg on elaboration of conditioned reaction (CR) of active avoidance in rats. Estimation of reaction dynamics by dynamic delta index allowed to increase the informational value of the experimental data with taking into account the direction of reaction shift and individual characteristic of the animal. AVP improved the elaboration of active avoidance CR, lowered variability of individual learning ability and did not influence the change of the number of intersignal reactions and short-latency escapes in the process of learning. It is suggested that the main site of AVP effect is the animal's reaction to conditioned sound stimulus.     

Effect of cadmium chloride on the processes of learning and memory in rats

Intraperitoneal injection of cadmium chloride (4 mg/kg) to rats before elaboration or reproduction of two-way avoidance conditioned reflex (TACR) disturbs both these processes. Deterioration of elaboration does not affect connections fixation and their subsequent reproduction. Injection of the substance before the elaboration of passive avoidance conditioned reflex (PACR) depresses elaboration and consolidation. Injection of cadmium chloride before testing of PACR preservation does not influence the processes of engrams reproduction. The observed disturbances cannot be connected with changes of animals motor activity.     

The effect of hypothalamic stimulation on food choice with rats maintained on different water-salt rations]

Electrical stimulation of the lateral hypothalamus in rats induces an increase of water intake and decrease of thresholds of eaten salty food. These effects are displayed in control animals and under salt diet and water deprivation. The hypothalamus stimulation relaxes the effects of "psychic distillation" of food which occur during spatial coincidence of conditioned signal of insipid food with salty reinforcement. Besides, the trans-switching of signal significance of conditioned stimuli connected with insipid and salty reinforcements is accelerated. The electrostimulation of the hypothalamus accelerates the elaboration of conditioned aversion of salty food inhibition of conditioned runnings toward corresponding food-box, and intensifies the existent state of thirst transforming it in the dominant motivation.     

Effect of hormones of the neurohypophysis on different types of behavioral responses in the rat

In experiments on male rats arginyl-vasopressin (AVP), lysyl-vasopressin (LVP) and vasotocin (VT) in doses of 0.005-0.010 mg/kg decreased motor activity and emotional behaviour in the open field test. In a dose of 0.001 mg/kg AVP significantly accelerated the elaboration of active avoidance; oxytocin delayed it, but LVP and VT had no significant influence. AVP also somewhat attenuated the elaboration of passive avoidance. None of the four studied peptides significantly affected the rate of elaboration of conditioned food-rewarded reaction to place.     

The characteristics of shuttle avoidance learning in spontaneously hypertensive and normotensive rats]

In spontaneously hypertensive (strain SHR) and normotensive (strain WKY) rats was studied the elaboration of conditioned reflex of active avoidance in shuttle box. In case when the shuttle box was divided by a partition the SHR rats learned worse than WKY rats. In shuttle chamber without partition the SHR rats, on the contrary, learned better that WKY ones. Such character of interlinear differences can be connected with properties of formation of the instrumental habit of deliverance from electropainful stimulus, because the presence of partition significantly hampered its fulfillment. The obtained results, compared with literature data, testify to the fact that differences of SHR and WKY rats in elaboration of conditioned reflexes are explained basically by the properties of their unconditioned activity and not of the associative processes.     

The retroactive action of paradoxical sleep deprivation and immobilization stress on the mechanisms of memory and passive avoidance in rats

Influence was studied of 48-hours deprivation of paradoxical sleep (DPS) and immobilization stress on conditioned reaction of fear and security--components of passive avoidance conditioned reflex (CRPA), with simultaneous studying of vertical, horizontal activity, grooming reactions and defecations in an illuminated chamber. The obtained results allow to conclude that DPS inhibits reproduction of memory traces of fear reaction but intensifies the process of learning and activity of memory traces of security reaction. Depending on condition of CRPA elaboration, DPS may disturb or, on the contrary, prolong preservation of passive avoidance. It has been found that the immobilization stress does not influence CRPA preservation and does not weaken the reaction of fear but increases the horizontal activity. It is suggested that the observed changes in behaviour and trace processes are connected with disturbance of sensory informational homeostasis of the nervous system at DPS.     

The long-term effect of acute hypoxic hypoxia on shuttlebox avoidance learning in rats

Long-term influence was studied of the acute hypoxic hypoxia seance on rats behaviour in situation of elaboration of the conditioned reaction of active avoidance of electric shocks in shuttle chamber. It was found that in 2.5-3 months after the hypoxia seance, the experimental animals significantly differed from the intact controls by dynamics of CR elaboration (rats which had hypoxia were ahead of the control ones) and by distribution of the conditioned reactions latencies (for experimental animals this distribution was shifted to minor values). The character of these behavioural shifts coincided with that observed in the group of rats with local unilateral hippocampus lesion. The obtained results and numerous data presented in literature on the influence of the hippocampus lesion on animals shuttle avoidance learning, allow to conclude that the seance of hypoxic hypoxia leads to the disturbance of the hippocampus function. This conclusion conforms to the data on diffusive death of the hippocampal and neocortical neurones as a result of hypoxia action.     

Functional role of the dorsal and ventral hippocampus in defensive behavior in the rat

Bilateral electrolytic lesions of the dorsal hippocampus of white rats were shown to facilitate elaboration of a conditioned response of active avoidance of pain shock in a shuttle-box. The lesions of the ventral hippocampus had no effect on conditioning. The ventral hippocampal lesions led to a complete failure to form differential inhibition. In rats with the dorsal hippocampal lesions an acquisition of partial (up to 60 per cent) discrimination of stimuli was possible. The differences in avoidance conditioning and elaboration of differential inhibition in rats with the dorsal and ventral hippocampal lesions are supposed to be caused by the changes of general excitability and emotional state of animals as well as by a specific role of the ventral hippocampus in memory consolidation.     

The effect of DMCM and diazepam on the behavior of rats subjected to ethanol exposure in the prenatal period]

White rats were given 4 g/lag daily of 40% ethyl alcohol from the 5th till the 20th day of pregnancy. Males of the off-spring from the 5th till 19th day were subjected to treatment with 0.6 mg/kg DMCM (4-ethyl-6, 7-dimethoxy-beta-carboline-3-carboxylate methyl ether) or 2.5 mg/kg of diazepam daily. It has been shown that both drugs normalize increased locomotor activity; treatment with DMCM corrects passive avoidance conditioned reflex retention; both drugs restore active avoidance conditioned reflex elaboration in rats alcoholized prenatally. Moreover, treatment with DMCM or diazepam restores correlations between behaviour indices and binding of 3H-diazepam which have been altered by prenatal alcoholization.     

Effect of vasopressin on changes in the behavioral reactions of rats induced by psychotropic substances

The effect was studied of arginyl-8-vasopressin (AVP) on changes in rats behavioural reactions, elicited by reserpine, haloperidol, aminazine, amitriptyline or nialamide. It has been shown that AVP administered intraperitoneally in a dose of 0.001 mg/kg, eliminates the deficit of elaboration of conditioned reaction of active avoidance produced by psychotropic drugs, without influencing the motor activity reduction developed after administration of these substances.     

Effect of destruction of the septum and hippocampus on the shuttle-box avoidance conditioning of the rat

Total destruction of the septum, the dorsal hippocampus (DH), or the lesion of the DH combined with that of the medial septal nucleus in rats was shown to facilitate elaboration of conditioned avoidance responses in a shuttle-box due to an increase of general excitability of the animals, and to cause significant impairment of internal inhibition formation. Lesions of the medial or the lateral septal nuclei as well as a combined lesion of the DH and the lateral septal nucleus had no significant effect on conditioning and internal inhibition elaboration. Therefore the septo-hippocampal connections had different functional directions during active defensive behaviour.     

The behavioral characteristics of rats selected for their learning capacity]

Experiments were conducted in rat strains selected for high (KHA) and low (KLA) levels of the elaboration of conditioned reflex of active avoidance in shuttle box. KHA rats, as compared with the KLA ones, showed considerably higher indices of learning the shuttle avoidance, a greater number of intersignal runs during learning, a higher level of motor activity under open field conditions and its more marked extinction. These data point at the role of both associative and non-associative processes in the formation of active avoidance reflex. During 5 days of reflex training the rats of both strains retained a high level of defecation until the end of the test that pointed at the emotional strain unceasing in spite of the automatization of the reflex.     

Developmental caspase-3 activation in the rat hippocampus is involved in the maturation of instrumental behavior

Previously the developmental switch to caspase-3 activation in the rat hippocampus has been shown during the third week of life. The goal of this study was to explore effects of caspase-3 inhibition during this period on learning in a two-way avoidance paradigm. On postnatal day 18, the pups were intracerebroventricularly administered with caspase-3 inhibitor Z-DEVD-FMK. Control groups were injected with either the control peptide Z-FA-FMK or saline. Caspase-3 inhibition, naturally activated in this critical period, was found to disturb the maturation of instrumental behavior. In particular, the young adult rats of Z-DEVD-FMK group displayed less effective elaboration of escape and active avoidance reactions in two-way avoidance paradigm, accompanied with a decrease in inter-trial crossings. However, associative components of the learning did not change after caspase-3 inhibition. Conditioned emotional behavior was, in general, similar in all groups, and the number of responses related to conditioned stimulus exploration did not differ in Z-DEVD-FMK and Z-FA-FMK groups. In spite of the deficit in active avoidance conditioning in Z-DEVD-FMK group, a significant increase in incomplete or preparatory reactions to conditioned stimulus was demonstrated suggesting that the association between predictive conditioned stimulus and possibility of crossing can be elaborated. The change of exploratory behavior is unlikely to be specific for caspase-3 inhibition, being similar in Z-DEVD-FMK and Z-FA-FMK groups.     

Effect of a cyclic enkephalin analog on the protein content in the hippocampal neurons of rats during the acquisition of a 2-way avoidance conditioned reflex

The protein content has been determined by means of cytointerferometry in neurons of fields CA-1 and CA-3 of the dorsal hippocampus in rats, which were trained in a conditioned reflex of two-way avoidance (CRTA) with the action of subcutaneously injected enkephalin cyclic analogue (ECA) in a dose 10 mkg. It has been found that after ECA injection the protein content in the neuronal nuclei of the hippocampal CA-3 field reduces. The acceleration of the CRTA elaboration occurring during the action of ECA is accompanied by a drastic increase of the protein content in the neuronal nuclei of the CA-3 field. The ECA administration to the rats of the active control groups to which were presented the same number of unpaired conditioned and unconditioned stimuli as during the CRTA elaboration also enhances the protein content in the neurons of the CA-3 field. The rats of all investigated groups in the neurons of the CA-1 field display no such significant shifts. The conclusion has been drawn that ECA produces a regulating influence on protein metabolism in hippocampal neurons depending on their functional state.     

The characteristics of higher nervous activity and of the brain benzodiazepine system in rats subjected to ethanol exposure in the prenatal period

Exposure to ethanol during pregnancy results in the alternation of 3H-diazepam binding to synaptosomal neocortical membranes from the rat offspring. In male experimental rats, 14 days of age, binding level diminished to 11%. In two-month-old control rats Scatchard plot was biphasic. It has been shown that prenatal exposure to ethanol leads to changes in the nature of binding in two-month-age experimental animals, as compared with the control ones. 3H-diazepam binding changes went along with behavioural deviations. In experimental rats locomotor activity was increased in the "open field" test, passive avoidance conditioned reflex retention was decreased and elaboration parameters of active avoidance conditioned reflex were changed, as compared with the control ones. The data obtained show that higher integrative functions were disturbed by prenatal alcoholization. Correlations between benzodiazepine receptor state and behaviour were studied.     

The effect of single maximal physical loading on the emotional behavior of rats

In experiments on 250 Wistar female rats the influence was studied of a single maximum and submaximum physical loads on the emotional behaviour and the state of conditioned activity. It has been established, that as a result of maximum possible run of the animals depression takes place of orienting investigatory activity in conditions of the "open field" and disturbance of elaboration and reproduction of the conditioned reflex of two-way avoidance. Normalization of these parameters took place in 48 hours after the maximum load action. Analogous effect was observed in the period of aftereffect of the submaximum physical load, characterized by lowering of the level of behavioural activity in the "open field", disturbance of the elaboration of two-way avoidance as a result of presumable increase of functional tonus of the brain inhibitory systems.     

Switching off of granule cells after intrahippocampal injection of colchicine eliciting the disappearance of evoked potentials and a deterioration in the development of a conditioned avoidance reflex in rats

The aim of the work was to study the involvement in the process of learning of synapses between the perforant path and granular cells of the hippocampal dentate fascia for formation of conditioned reflex (CR) of active avoidance elaborated in response to electrostimulation of the perforant path. For solving this task, the property was used of the neurotoxin colchicine in a definite concentration to abolish selectively the fascia cells. One month after colchicine injection, destruction of granular cells was observed, disappearance of the dentate fascia focal evoked potentials and considerable deterioration of elaboration of active avoidance CRs. Administration of saline solution in control experiments did not elicit such changes. The obtained results show the decisive role of entorhinal input to the hippocampus in the used learning model.     

Avoidance reaction and defensive reflex in the rabbit based on hypothalamic stimulation inducing strokes of the paws

In experiments on rabbits electrical stimulation of the medial hypothalamic area elicited a biphasic reaction: running during the current action and species-specific reaction of kicking the floor with the hind limbs in poststimulous period. Conditioning with acoustic stimulus led in the half of rabbits to elaboration of a habit of jumping on a safe platform in experimental model of active avoidance and to a weak conditioned reaction of kicking without running in the model of classical defensive reflex. The number of conditioned limb kicks was 7-10 times less than that of analogous responses to the reinforcing stimulus. With the increase of the number of combinations, the conditioned habit of kicking became deteriorated: the response became weaker and its latency more prolonged. The results of experiments are discussed in the light of Anokhin's theory of functional system of goal-directed behavioural act.     

Fromation of forward and reverse connections during elaboration of a classical and instrumental acid-defense conditioned reflex

During elaboration of a classical acid defensive conditioned reflex to passive lifting of a foreleg in dogs, the reinforcing stimulus--acid elicited an extension of the leg via backward connection. At the initial stage of elaboration of an instrumental avoidance reflex, the reinforcing stimulus called forth an extension of the leg, whereas at the stage of a stable reflex it produced a flexion.