[Critical phases of the brain development]. / Kriticheskie periody razvitiia golovnogo mozga.

Various effects were shown to act alter the proceeding of histogenetic processes in the embryonic neural tissue. Studies in mice revealed that, depending on the embryogenesis stage when a lack of serotonin occurred, the lack of this monoamine entails either death of the embryo or a teratogenic effect, or underdevelopment of brain structures. In the rat model of a shorten hypoxia, a disorder of neural tissue histogenesis in early stages of development, was found, as well as a reduction of its sensitivity to lack of oxygen by the end of embryogenesis.

Antinociceptive effects of brain rewarding system in the developing rabbit: behavioral and electrophysiological analysis.

The modulating effects of electrical stimulation (ES) in the reward sites (RSs) of the hypothalamus and adjacent brain areas on the defensive reaction (DR) in response to peripheral noxious stimulation (PNS) and on evoked potentials (EPs) recorded in the thalamic centromedian-parafascicular complex (CM-Pf) to the same PNS have been investigated in 20-40-, 41-60-day old and 3-5-month old rabbits. Previously, RSs were identified by the method of intracranial self-stimulation (ICSS). Behavioral and electrophysiological testings successively performed on each rabbit first awake and then anaesthetized have revealed the ES in all investigated RSs to inhibit DR and EPs. These effects were not observed if the stimulating electrode tip was localized in emotionally neutral brain sites. In behavioral testings, the antinociceptive effect of rewarding stimulation was positively correlated with the ICSS intensity in given brain sites regardless of the age of the rabbits. In electrophysiological testings, a similar dependence of nociceptive EPs inhibition on emotional values of stimulated brain sites (determined as a rate of lever pressings during ICSS) was discovered only in 20-40-day and 3-5-month old rabbits. Stimulation of low emotional value RSs (low rate (LR)-rabbits) exerted a weaker inhibitory influence in 3-5-month old rabbits in comparison with 20-40- and 41-60-day old rabbits both in behavioral and electrophysiological testings. The weakest antinociceptive effect of rewarding stimulation among the rabbits with a high rate of lever pressings (HR-rabbits) was found in 41-60-day olds in electrophysiological testings. In 41-60-day old rabbits, we have observed a discrepancy between the behavioral analgesia and its electrophysiological correlates. It may be suggested that the observed peculiarities of antinociceptive influences produced by RSs ES are determined by the age factors of neurotransmitter brain systems.

Role of the vagus nerves in neophobia and conditioned-reflex taste aversion.

Combination of ingestion of water with discomfort in rats with intact vagus nerves on selection between water and saccharine solution (an unknown taste) produced aversion not to water but to saccharine, with sharp increases in water consumption. In vagotomized rats, this combination led to a significant increase in saccharine consumption with no change in water intake. After extinction of neophobia to saccharine, combination of ingestion of water with rotation induced aversion to water in both groups (this being delayed in vagotomized rats). Vagus nerve signaling activity in selection conditions appears to determine the choice of behavior strategy.

Conditioned reflex responses of the sympathetico-adrenal system to an aversive taste stimulus.

Studies were carried out on male and female rats in which the effects of isolated presentation of a conditioned stimulus (a saccharine solution) to which the animals had previously developed conditioned reflex taste aversion (RTA) on the level of urinary catecholamine secretion were determined. The studies showed that presentation of an aversive taste stimulus without reinforcement by a negative stimulus increased the levels of urinary adrenaline, noradrenaline, and dopamine secretion; this repeated, albeit more weakly, the effects of the negative reinforcement (angular acceleration) used for development of RTA. After presentation of the isolated aversive taste stimulus, the greatest increase in catecholamine excretion affected adrenaline, which indicates an anxiety state (fear). There was also a significant increase in noradrenaline excretion in these conditions. The accompanying increase in dopamine excretion in experimental and control animals showed this change to be largely nonspecific in nature, and to result from the experimental procedures. Isolated presentation of the conditioned taste stimulus elicited significantly greater increases in urinary catecholamine excretion in males than in females. It is suggested that the time for which the RTA is retained could be increased by activation of the sympathetico-adrenal system resulting from presentation of the nonreinforced taste stimulus which had acquired aversive properties.

[The role of the vagus nerves in the manifestations of neophobia and conditioned-reflex taste aversion]. / Rol' bluzhdaiushchikh nervov v proiavleniiakh neofobii i uslovnoreflektornoi vkusovoi aversii.

Vagotomized rats given a choice between water and an unfamiliar 0.2% saccharin solution ingest comparable amounts of both fluids over 2.5 weeks of testing. Saccharin intake in sham-operated rats grows steadily (attenuation of taste neophobia), with water intake being unchanged. After the pairing of water intake with rotation saccharin intake in vagotomized rats grows and in sham-operated animals decreases significantly, whereas water intake in the latter increases sharply. Thus, the rats with retained vagal innervation exhibit aversion to saccharin, substance with an unfamiliar taste, but not to water paired with a discomfort. After two-week elimination of neophobia to saccharin, the pairing of water intake with rotation brings into the acquisition of aversion to water in the first days of choice testing in sham-operated rats; similar aversion in vagotomized rats appears with retardation (on the 4th to 6th day).

[The conditioned-reflex reaction of the sympathoadrenal system to an aversive taste stimulus]. / Uslovnoreflektornaia reaktsiia simpatiko-adrenalovoi sistemy na aversivnyi vkusovoi stimul.

A non-reinforced taste stimulus with aversive properties was found to increase the level of excretion of adrenaline, noradrenaline and dopamine, thus reflecting occurring anxiety. The dopamine increase seems to be due to unspecific reasons of the experimental procedure. Catecholamines increase more in males rather than in females. The conditioned taste aversion seems to be preserved for a longer period of time in activating of the sympathetic-adrenal system.

[Sex dimorphism in the patterns of conditioned-reflex taste aversion and orienting-exploratory and passive-defensive behaviors]. / Polovoi dimorfizm v patternakh uslovnoreflektornoi vkusovoi aversii i orientirovochno-issledovatel'skogo i passivno-oboronitel'nogo povedeniia.

The patterns of conditioned taste aversion (CTA) and of some other types of behaviour were compared in adult male and female Wistar rats. Correlations between the CTA variables, on the one hand, and those of the exploratory and defensive behaviours, on the other, were shown. Females displayed initially less expressed CTA and more rapid its extinction than males. While tested in the open field, in a six-arm radial maze and in a special enclosed cubic chamber with holes in its vertical walls the females demonstrated higher levels of exploratory and locomotor activities with lower levels of emotionality and defensive behaviour than males. Sex differences were revealed in correlations between variables of CTA and behavioural responses under study. Thus, CTA patterns appear to be one of the manifestations of sexual dimorphism in non-reproductive behaviour.

[The influence of naloxone on the antinociceptive effects of the brain system of negative reinforcement in the developing rabbit]. / Vliianie naloksona na antinotsitseptivnye éffekty mozgovoi sistemy otritsatel'nogo podkrepleniia u razvivaiushchegosia krolika.

Participation of opioidergic mechanisms in implementation of inhibitory effects of the brain "punishment areas" upon nociceptive afferentation, was studied. The antinociceptive effect of electrical stimulation of the "areas" was either enhanced or reduced by naloxone depending on the current strength. The role of the opioids was shown to diminish with age. The results suggest that the opioids are more significant in the realization of the antinociceptive influences woned by stimulation of the "brain rewarding" than the "brain punishment areas".

[The characteristics of training 1.5- to 4.5-month-old puppies to spatial-temporal alternation]. / Osobennosti obucheniia 1.5--4.5-mesiachnykh shchenkov prostranstvenno-vremennomu cheredovaniiu.

The dynamics of formation and realization of alternation between six feeding troughs at meat refreshment at different time of a day has been studied on four groups of puppies and adult dogs. Essential age differences in time of formation and realization of perfect alternation as well as the number of refusals from fulfillment of conditioned reflex programme were revealed. The results obtained suggest the necessity to take into account different manifestations of interactions of the organism with environment at periodization of the development of higher nervous activity.

[The participation of opioids in the antinociceptive effect induced by the stimulation of hypothalamic "pleasure zones" in 20- to 30-day-old rabbits]. / Uchastie opioidov v antinotsitseptivnom éffekte, vyzvannom stimuliatsiei gipotalamicheskikh "zon nagrady", u 20--30-sutochnykh krolikov.

The involvement of opioid peptides in the mediation of inhibitory influences of the positive reinforcement system ("reward areas") on the evoked potential (EPs) recorded in the thalamic parafascicular complex (CM-Pf) in response to the nociceptive electrodermal stimulation of the hind paw in 20-30 day rabbits has been studied. Electrical stimulation of "reward areas" identified in the preliminary behavioural experiments inhibited the EPs. The systemic injection of naloxone potentiated the antinociceptive effect of "reward areas" stimulation in 75% of cases under the incomplete inhibition of EPs (the decrease of EPs amplitude) but decreased its inhibitory effect in 87% of cases under the complete inhibition of EPs. Naloxone did not change the inhibitory effect of "reward areas" stimulation suggesting to the relationship of analgesic "reward areas" function with nonopioid mechanisms too. On the basis of the comparison of the present data and the ones obtained before it can be inferred that opioid mechanism in realization of antinociceptive influence of "reward areas" stimulation on EPs in CM-Pf is more important for 20-30 day rabbits compared with 41-60 day ones. The correlation of the phenomenon under investigation with the formation of neurotransmitter systems has been discussed.