[Neurotensin influence on painful stress afteractions in rats with neurotoxic damages of serotoninergic structures of brain substantia nigra].

The purpose of the research was to reveal the features of neurotensin influence on behavior of rats with damages of 5-HT structures of substantia nigra. Changes of recall of passive avoidance conditioned reactions, and also painful stimulation aftereffects on locomotor activity of rats in "open field" were studied. It was shown that neurotoxin 5,7-DOT administration into substantia nigra impaired recall of passive avoidance reactions and as well weakened oppressive aftereffects of painful stimulation. Administration of serotonin 5-HT1A receptors antagonist p-MPPF insert similar influence on aftereffects of painful stimulation. Neurotensin microinjections into caudate nucleus just before painful stimulation prevented disturbances of defensive behavior and its aftereffects evoked by neurotoxin. Neurotensin administration into substantia nigra in 24 h after painful stimulation didn't exert any significant influence on passive avoidance reactions but increased motor activity against a background of its recall. Effects of neurotoxin administrations into substantia nigra connected with weakened of painful stress influence on motor activity in rats. The prevention of this effect development after neurotensin administrations into caudate nucleus may be specified by recovery of recall passive avoidance reactions destroyed by neurotoxin action and is explained by normalization of relationships balance of 5-HT and dopaminergic brain systems.

[Reproduction of passive avoidance reactions after neurotensin microinjection into nucleus accumbens of rat brain against the background of reserpine action].

The purpose of the study was to reveal the features of the influence of neurotensin injected into the nucleus accumbens on behaviour of rats after systemic administration of reserpine in the dose of 2 mg/kg. Reprodution of passive avoidance conditioned reactions, painful stimulation aftereffects on locomotor activity in the "open field", and behavior in the elevated plus-maze were studied. It was shown that reserpine administration impaired the reproduction of passive avoidance reactions and weakened the oppressing aftereffect of painful stimulation, which can be due to a decrease in anxiety in rats. Neurotensin prevented disorders in the defensive behavior evoked by reserpine and intensified the state of anxiety in the elevated plus-maze. The positive influence ofneurotensin on the reproduction of passive avoidance can be associated with the recovery of the anxiogenic effect of painful stimulation destroyed by reserpine. Thus, neurotensin injected into the nucleus accumbens could normalize the balance of brain monoaminergic systems.

[Emotional state variations in rats during recall of passive avoidance reactions after neurotensin administration into nucleus accumbens of the brain].

Behavioral effects of neurotensin administration into the nucleus accumbens were studied in rats with neurotoxic lesions of serotoninergic structures of the dorsal raphe nucleus or periaqueductal grey matter. Changes in recall of passive avoidance conditioned reactions and aftereffects of painful stimulation in the locomotor activity were studied in the "open field" and elevated plus-maze and T-maze tests. The toxin administration into the dorsal raphe nucleus did not impair the recall of the passive avoidance reactions, but enhanced the oppressive aftereffects of painful stimulation, which can specify the development of anxiety in rats. The toxin administration into the periaqueductal grey matter had an opposite effect, which can be considered as a manifestation of the panic state. Neurotensin weakened the above mentioned effects of the toxin and, depending on the evoked emotional disorders, produced the anxiolytic or antipanic effects.

Serotoninergic mechanisms of the effects of neurotensin on passive avoidance behavior in rats.

The aim of the present work was to identify the features of the actions of neurotensin on administration into the substantia nigra or dorsal cervical nucleus on the reproduction of passive avoidance reactions in rats. The results showed that the action of neurotensin administered into the substantia nigra was accompanied by sharp reductions in passive avoidance reactions, while administration into the dorsal cervical nucleus, conversely, led to increases in these reactions and slowing of their extinction. The effects of microinjections of the serotonin 5-HT(1A) receptor agonist 8-hydroxydipropylaminotetraline (8-OH-DPAT) into these brain structures were analogous to the effects of neurotensin. The different behavioral effects of administration of neurotensin corresponded to identifiable changes in the levels of serotonin and its metabolite 5-hydroxyindoleacetic acid in the caudate nuclei of the brain. These data led to the conclusion that the effects of neurotensin on passive avoidance behavior are associated with the regulation of the emotional state of the animals via actions on the functions of brain serotoninergic structures.

[Involvement of serotoninergic brain structures in the mechanisms of neurotensin effect on passive avoidance in rats].

The purpose of the research was to reveal the features of neurotensin (administered in substantia nigra or dorsal raphe nucleus) effect on recall of passive avoidance reactions in rats. It was shown that the effect of neurotensin injected into the substantia nigra was characterized by a sharp reduction of passive avoidance reactions. On the contrary, injection of the substance in the dorsal raphe nucleus led to an intensification of these reactions and delay of their extinction. The effects of microinjections of serotonin 1A receptor agonist, 8-hydroxy-dipropylaminotetralin (8-OH-DPAT), into the mentioned brain structures was similar to that of neurotensin. Changes in the content of serotonin and its metabolite 5- hydroxyindoleacetic acid (5-HIAA) in the caudate nucleus corresponded to various behavioral effects. The conclusion was made that neurotensin effect on the passive avoidance behavior is related to regulation of emotional state of animals mediated by its action on the function of the serotoninergic brain structures.

[Effect of neurotensin on the behavior of rats with damaged serotoninergic neurons under immobilization stress].

It was shown that the immobilization of animals has led to reducing of vertical and horizontal locomotor activity in the "open field" and decreasing of number of conditioned food-procuring reactions into T-maze. The damages of serotoninergic neurons produced via local injections of selective neurotoxin 5, 7-dihydroxytriptamine into dorsal raphe nucleus intensified behavior alterations. Neurotensin administrations reduced effects of neurotoxin: the rats locomotor activity and quantity of conditioned reactions into T-maze were kept at the phone level just after immobilization as well as next two days. The results indicate the important protective significance of neurotensinergic brain structures for ensuring of adaptive behavior of animals with damaged serotoninergic neurons under emotional stress conditions. It is supposed that neurotensin normalizing influences on behavior is connected to a restoration of balance of dopamine-and serotoninergic brain structures interaction.

Aftereffects of microinjections of neurotensin into the substantia nigra of the brain on conditioned motor responses in rats with lesions to serotoninergic neurons.

The effects of neurotensin microinjections into the substantia nigra of the brain on the performance of motor reactions in response to positive (food reinforcement) and negative (unreinforced) conditioned signals were studied, along with the characteristic aftereffects of these microinjections in rats with lesions to serotoninergic neurons in the dorsal cervical nucleus. Lesions were produced by local administration of the selective neurotoxin 5,7-dihydroxytryptamine. Microinjections of neurotensin were found to weaken the disinhibitory effects of neurotoxin on extinction of intersignal responses and extinction of conditioned motor reactions in response to presentation of negative stimuli, but to have no marked effect on the performance of reactions evoked by positive conditioned signals. Changes persisted into subsequent experiments without peptide microinjections. Measurements of the level of preference of the animals for one quadrant of the experimental chamber showed that operated rats avoided occupying the test quadrant and preferred to locate themselves in the opposite quadrant. Neurotensin released this effect of the neurotoxin. These results lead to the conclusion that these behavioral effects of neurotensin are associated with its normalizing influences on the motivational-emotional state of the animals with lesions to serotoninergic neurons and may also be due to the formation in the animals of a contextual conditioned emotional state, which aids optimization of the adaptive functions of the brain.

Characteristics of the actions of neurotensin on motor reactions in rats in response to positive and negative conditioned signals.

This study addressed the effects of microinjections of neurotensin into the caudate nucleus and substantia nigra on the performance of motor reactions in response to positive and negative conditioned signals, as well as the post-effects of microinjections in subsequent experiments. Neurotensin had positive effects on the extinction of non-reinforced motor reactions. Neurotensin had no effect on the number of motor responses to the non-reinforced signal, though the number decreased in subsequent experiments. There was an increase in the latent period of responses as compared with controls. The effect of neurotensin at the level of the caudate nucleus was more marked than that at the level of the substantia nigra. Neurotensin microinjections had no marked effect on performance of conditioned responses to positive signals. The behavioral effects of neurotensin are associated with normalization of the interactions of the brain's monoaminergic systems. It is suggested that the positive actions of neurotensin on extinction of motor responses to negative signals result from the formation of a contextual conditioned emotional state in the animals, this facilitating optimization of conditioned reflex activity.

[Delayed effects of neurotensin microinjections into the substantia nigra on conditioned motor reactions of rats with lesions to serotoninergic neurons]. / Posledeistvie mikroin''ektsii neirotenzina v chernuiu substantsiiu mozga na uslovnye dvigatel'nye reaktsii krys s povrezhdeniem serotoninergicheskikh neironov.

Behavioral effects of neurotensin microinjections into the brain substantia nigra of rats with neurotoxic (5,7-dihydroxytryptamine) lesions of serotoninergic neurons in the dorsal raphe nucleus were studied. It was shown that neurotensin facilitated extinction of conditioned and intertrial reactions to negative (unreinforced) stimuli, but did not change the actualization of positive (with water reward) conditioned signals. Neurotensin-induced effects persisted in subsequent experiments without injections of the peptide. Neurotensin injections reduced the negative emotional states of lesioned animals in the arena during testing conditioned preference. It was concluded that the behavioral effects of neurotensin can be explained by the formation in the lesioned animals of the situational emotional state facilitating adaptive brain functions.

[Specifics of the neurotensin effect on rat motor responses to positive and negative conditioned stimuli]. / Osobennosti vliianiia neirotenzina na dvigatel'nye reaktsii krys v otvet na pozitivnye i negativnye uslovnye signaly.

Comparative analysis of effects of neurotensin microinjections into caudate nucleus and substantia nigra on thirst-motivated motor conditioned reactions in rats, was performed. The microinjections facilitated extinction of conditioned reactions in response to negative stimuli and did not affect realization of responses to positive conditioned signals. Behavioral effects of neurotensine in rats are connected with the normalising of motivational and emotional states of animals and may be explained by restoration of monoaminergic systems interaction.

The effects of microinjection of neurotensin into the caudate nucleus of the rat brain on the performance and extinction of a conditioned motor reflex.

The studies reported here demonstrate that microinjection of neurotensin into the caudate nucleus of the rat brain facilitated extinction of a conditioned motor reflex with reinforcement provided by drinking. Neurotensin had positive effects on the process of post-extinction inhibition in subsequent experiments. Neurotensin microinjections had no marked effect on the performance of the conditioned reflex, though it weakened the emotional tension of the animals in an "open field" test. It is concluded that the functional importance of neurotensin at the level of the caudate nucleus is associated less with the regulation of motor function than with optimizing the motivational-emotional state of the animal.

[Influence of neurotensin on behavior of rats with lesions in serotonergic neurons]. / Vliianie neirotenzina na povedenie krys s povrezhdeniem serotoninergicheskikh neironov.

After serotonergic lesion by administration of 5,7-dihydroxytryptamine into the dorsalis raphe nucleus, effects of neurotensin microinjections into the caudate nucleus and substantia nigra on rat behavior were compared. Serotonergic lesions resulted in motivated excitement of rats manifested as an increase in the number of intersignal motor reactions during realization and, particularly, extinction of thirst conditioned reflex. Neurotensin microinjections into the caudate nucleus facilitated extinction of the conditioned reflex both in operated and control rats, but such microinjection into the substantia nigra facilitated this process only in operated animals. Neurotensin did not change conditioned reflex realization in both groups of animals but decreased emotional excitement of rats in the "open field". The behavioral effects of neurotensin in operated rats are connected with normalization of motivational and emotional states of animals and may be explained by recovery of interaction between the dopamine- and serotonergic systems. It is suggested that the mechanisms of this normalizing effects of neurotensin at the levels of the caudate nucleus and substantia nigra are different and are associated preferentially with its action either on dopamine- or serotonergic structures.

[Effect of neurotensin injections into caudate nuclei on realization and extinction of conditioned motor reflex in rats]. / Vliianie mikroin''ektsii neirotenzina v khvostatye iadra mozga krysy na realizatsiiu i ugashenie uslovnogo dvigatel'nogo refleksa.

It was shown that neurotensin microinjections into the caudate nuclei facilitated of a conditioned reflex but not affected its realization. Besides, neurotensin was shown to have a positive aftereffect on extinction. Motor activity of rats in the "open field" was augmented after neurotensin administration. A conclusion was drawn that the functional effect of neurotensin administration into the caudate nuclei is connected with the normalization of the motivational and emotional state of an animal rather than with the regulation of the motor function.

[An analysis of the behavioral effects of stimulation of the dopamine D2 receptors at the level of the ventral tegmental area in the rat brain]. / Analiz povedencheskikh éffektov stimuliatsii dofaminovykh D2-retseptorov na urovne ventral'noi oblasti pokryshki mozga krysy.

It was shown that intracerebral injections of D2 dopamine receptor agonist quinpirol after systemic administration of D2 antagonist sulpiride inhibited both locomotor and food-procuring activity in rats. It was concluded that this effect is connected with involvement of the negative feedback mechanisms of dopaminergic neurons. The involvement of this mechanism into the regulation of the motivated behavior seems to require the definite level of dopaminergic structures.

Role of enkephalinergic brain structures in regulating motivated behavior in rats with lesioned serotoninergic neurons.

The behavioral effects of injections of enkephalin into the substantia nigra or dorsal raphe nucleus were studied in rats with lesioned serotoninergic structures. Lesions were produced by intracerebral administration of the neurotoxin 5,7-dihydroxytryptamine. Treated rats showed normalization of conditioned drinking reflex extinction. It is proposed that there is a tight connection between the normalizing effects of enkephalin on rat behavior in conditions of deficient brain serotoninergic system function and increases in the efficiency of presynaptic inhibition of dopaminergic neurons.

[Role of enkephalinergic structures of the brain in regulation of motivated behaviour in rats with damaged serotoninergic neurons]. / Rol' énkefalinergicheskikh struktur mozga v reguliatsii motivirovannogo povedeniia krys s povrezhdeniem serotoninergicheskikh neironov.

Enkephaline microinjections into the substance nigra or dorsal raphe nucleus improved extinction of conditioning in rate. The findings suggest an interrelationship between the brain enkephalinergic structures and improving of efficiency of the presynaptic inhibition in dopaminergic neurons.

[The correlation of dopamin- and enkephalinergic influences on rat conditioned-reflex activity]. / Sootnoshenie dofamin- i énkefalinergicheskikh vliianii na uslovnoreflektornuiu deiatel'nost' krys.

Behavioural effects of enkephalin microinjections into substantia nigra of rat brain were studied in short time after intrastriatal administration of 6-hydroxydopamine (6-OHDA). It was shown that such microinjections improved conditioned activity of animals. A conclusion was made that the role of enkephalinergic brain structures in compensatory processes in acute period of development of 6-OHDA neurotoxic action was related to increase in efficiency of the mechanisms of self-regulation of dopamine neurons.

[Are the serotonin receptors life receptors?]. / Iavliutsia li serotoninovye retseptory "retseptorami zhizni"?

The paper gives evidence for the fact that serotonin and serotonin receptors are responsible for the occurrence of primary contractions of smooth muscles, primary cardiac contractions and primary brain electric activity (EEG genesis). It is concluded that the function of the smooth muscle, brain and heart cannot take place without serotonin and its receptors. This suggests that the serotonin receptors are life ones.