Biogenic amine content in the brains of rats with different levels of resistance to emotional stress.

The levels of biogenic amines and of a number of the products of their metabolism were studied in the hypothalamic nuclei in Wistar and August rats, which have different levels of resistance to emotional stress; levels were also studied in structures functionally and anatomically associated with the hypothalamic nuclei, i.e., the reticular formation of the midbrain, the amygdaloid body, the septum, the locus ceruleus, the dorsal cervical nucleus, and the ventral region of the tegmentum. The genotype was found to determine the level of metabolism of biogenic amines in structures of the central nervous system in conditions of emotional stress. In August rats, the activities of the dopaminergic and serotoninergic systems, which are stress-limiting, decreased to a greater extent during 24-hour immobilization stress. Adrenaline levels in structures of the central nervous system in August rats were higher during stress. Changes in the contents of biogenic amines in the paraventricular and ventromedial nuclei of the hypothalamus in Wistar and August rats could affect the preganglionic neurons of the autonomic nervous system.

Delta-sleep-inducing peptide sequels in the mechanisms of resistance to emotional stress.

The aim of this study is to investigate time-related changes in substance P (SP), beta-endorphin (BE), and corticosterone (CORT) levels due to DSIP aftereffects in the control and stress rats. Experiments were carried out on male Wistar and August rats. The SP and BE immunoreactivity in the hypothalamus and plasma samples was determined radioimmunologically. Blood CORT level was determined radioimmunologically. The rats were stressed at nighttime in special cages and tied by tails to the back side of the cage. The stress experiments were repeated for 12 hours for 5 days. There were 6 groups: 1. control animals, 2. stress animals, 3. rats that received DSIP in a dose of 60 nmol/kg one hour before decapitation, 4. rats in which DSIP was injected 24 hour before decapitation, 5. stressed rats in which DSIP was injected one hour before decapitation during the 5th exposure to stress, 6. stressed rats to which DSIP was injected 12 hours before the 5th exposure to stress, i.e., 24 hours before decapitation. Our experiments showed that DSIP administration induced marked changes in SP, BE, and CORT levels in hypothalamus and blood plasma. This suggests that the long-term stress-coping effect of DSIP depends on considerable changes in the level of other oligopeptides and hormones induced by DSIP. Evidently, DSIP triggers these processes inducing a cascade of interrelated molecular reactions radically different in animals with different resistance to emotional stress. This cascade of sequential reactions is different in Wistar and August rats differing by their resistance to emotional stress. DSIP administration stimulates the mechanism of resistance in August rats to a lesser extent than in Wistar animals.

[Changes in the content of substance P, beta-endorphin and corticosterone in the hypothalamus and blood of rats with emotional stress after the administration of the delta sleep-inducing peptide]. / Izmenenie soderzhaniia veshchestva P, beta-éndorfina i kortikosterona v gipotalamuse i krovi krys pri émotsional'nom stresse posle vvedeniia peptida, vyzvaiushchego del'ta-son.

The aim of this study was to investigate time-related changes in substance P (SP) beta-endorphin (BE), and corticosteron (CORT) levels induced by DSIP administration in rats subjected to emotional stress. Experiments were carried out in male Wistar and August rats with different resistance to emotional stress. At night rats were tied by their tails to the backside of the special cages. These stress-inducing procedure was repeated for 12 hours daily in the course of 5 days. SP and BE immunoreactivity in the hypothalamus and plasma and blood CORT level were determined radioimmunologically. Six groups of animals were formed: 1. control animals; 2. stressed animals; 3. rats which received DSIP in a dose of 60 nmol/kg one hour before decapitation; 3. rats to which DSIP was injected 24 hours before decapitation; 5. stressed rats to which DSIP was injected one hour before decapitation during the 5th exposure to stress; 6. stressed rats to which DSIP was injected 12 hours before the 5th exposure to stress, i.e. 24 hours before decapitation. Our experiments showed that DSIP administration induced marked changes in SP, BE, and CORT levels in the hypothalamus and blood plasma. This suggests that long-term stress-coping effects of DSIP in underlied by considerable changes in the content of other oligopeptides and hormones. Evidently, DSIP triggers these processes inducing a cascade of interrelated molecular reactions which are different in Wistar and August rats. It seems likely that DSIP administration stimulates the mechanisms of resistance in August rats to a lesser extent than in Wistar rats.

[The open-field test as a prognostic criterion of resistance to emotional stress in Wistar rats]. / Test otkrytogo polia kak prognosticheskii kriterii ustoichivosti k émotsional'nomu stressu u krys linii Vistar.

The open-field test was studied as a predictive behavioural criterion of resistance to emotional stress. Emotional stress was induced in Wistar rats by immobilization with simultaneous electrical skin stimulation 3 days after behavioural testing. Severity of stress was evaluated by the rate of survival and changes in the weight of thymus and adrenals. Rats which displayed longer latencies of the first movement in the open field and of crossing the central areas, lower locomotor and exploratory activity, higher rate of defecation had lower survival rate and more pronounced adrenal hypertrophy in stress.

[The effect of the combined action of chronic gamma irradiation and emotional stress in rats]. / Effekty kombinirovannogo deistviia khronicheskogo gamma-oblucheniia i émotsional'nogo stressa u krys.

Combined gamma irradiation and stress increased the emotional response in rats. The number of lymphoid cells increased significantly in the bone marrow, thymus and spleen, whereas fewer reticulocytes, neutrophils and thrombocytes were found in the peripheral blood.

[The physiological properties of endogenous oligopeptides that enhance resistance to emotional stress]. / Fiziologicheskie svoistva éndogennykh oligopeptidov, povyshaiushchikh ustoichivost' k émotsional'nomu stressu.

In the work was studied the effect of the delta-sleep inducing peptide (DSIP) on the substance P (SP) content in the hypothalamus of August rats genetically predisposed to emotional stress. The hypothalamic SP level increased 3 h and 6 h after systemic i. p. DSIP administration in doses of 60 and 120 nM/kg. The effects of i. p. DSIP administration on the hypothalamic SP were studied on an experimental model of aggressive-conflict behaviour in rats. The peptide was injected before the animals were exposed to stress. Quintuple DSIP administration in the above mentioned doses before exposing rats to stress induced highly significant increase in the hypothalamic SP. Single DSIP injections also significantly elevated SP values, reduced the adrenal hypertrophy and the thymus involution resulting in an increase of the rats' survival as compared to the control animals exposed to stress without DSIP. The antistressor effect of DSIP is assumed to be realized through the increase of the hypothalamic SP which is a factor enhancing the animal resistance to emotional stress.

Delta sleep-inducing peptide as a factor increasing the content of substance P in the hypothalamus and the resistance of rats to emotional stress.

The influence of delta sleep-inducing peptide (DSIP, 60 and 120 nmole/kg, intraperitoneally) on the content of substance P (SP) in the hypothalamus of rats was studied in male rats of the August line. It was demonstrated that the administration of DSIP significantly increases the average content of SP in the hypothalamus, as well as its content in animals resistant to and predisposed to emotional stress. A daily one-time administration of DSIP before placing the rats in conditions of stress increases the content of SP in the hypothalamus which was decreased during emotional stress. The preliminary one-time administration of DSIP to animals subjected to a stressor influence also increases the SP content in the hypothalamus. It was established that a one-time administration of DSIP in a dose of 60 nmole/kg sharply decreases the classical manifestations of stress such as the hypertrophy of the adrenals and involution of the thymus.

[Met-enkephalin restores self-stimulation behavior in rabbits after destruction of the hypothalamic nuclei]. / Met-enkefalin vosstanavlivaet povedenie samostimuliatsii u krolikov posle razrusheniia iader gipotalamusa.

Contralateral lesions of ventromedial and lateral hypothalamic nuclei inhibited hypothalamic self-stimulation in rabbits. Intracerebroventricular injection of metenkephalin evoked the restoration of self-stimulation behavior.

[The delta sleep-inducing peptide as a factor enhancing the content of substance P in the hypothalamus and the resistance of rats to emotional stress]. / Peptid, vyzyvaiushchii del'ta-son, kak faktor, povyshaiushchii soderzhanie veshchestva P v gipotalamuse i ustoichivost' krys k émotsional'nomu stressu.

The influence of the delta-sleep inducing peptide (DSIP, 60 and 120 nmol/kg, intraperitoneally) on the content of substance P (SP) in rats hypothalamus was studied on males of August line. DSIP administration significantly increased the mean SP content in the hypothalamus and also its content in animals, stable and predisposed to emotional stress. Daily DSIP administration before putting the rats in conditions of stress increased the SP content in the hypothalamus decreased at the emotional stress. Preliminary single DSIP administration to the animals subjected to stress also increased the SP content. Single DSIP administration in a dose of 60 nmol/kg sharply reduced classical stress manifestations, such as hypertrophy of adrenals and thymus involution.

Action of beta-endorphin antiserum of different antibody titres on thermal or tail-shock pain in rats.

Intravenous injection of beta-endorphin antiserum (AS) with antibody titres of 1:1,600, 1:3,200, 1:12,800, and 1:20,000 decreased the voltage threshold in the tail-shock test (electrocutaneous nociceptive stimulus) in rats for 2 days, after which time control levels were regained. In the case of AS of titres 1:12,800 and 1:20,000 this threshold then increased to above control levels for about 40 and 100 days, respectively. This effect was abolished by naloxone. In the same rats, an injection of AS of titre 1:1,600 did not alter the latency of the tail-flick test (thermal nociceptive stimulus) but AS of titres 1:3,200, 1:12,800, and 1:20,000 decreased it for 1-4 h, the actual length of time being titre-dependent. After control levels had been regained, there was no further change in latency in the tail-flick test in the subsequent 42 days. Injection with preimmune serum did not change either voltage threshold or latency in the two tail-stimulation tests in control rats. Thus the hyperalgesic short-term effect seen in response to treatment with beta-endorphin AS was more pronounced in response to an electrocutaneous stimulus than to a thermal one, and the long-term selective analgesic effect was present in response to rats given electrocutaneous stimulation but not to thermal stimulation. It is proposed that beta-endorphin AS has a two-stage selective effect: a reduction in beta-endorphin release followed by a 'rebound' increase.

[Effects of beta endorphin and delta-sleep inducing peptide on resistance to emotional stress]. / Vliianie beta-éndorfina i peptida, vyzyvaiushchego del'ta-son, na ustoichivost' k émotional'nomu stressu.

Enzyme immunoassay was used to study the contents of beta-endorphin and delta-sleep inducing peptide (DSIP) in blood and hypothalamus in rats of Wistar and August lines under acute emotional stress. The stress-resistance of the animals was determined by using preliminary behavior tests. The rats were divided into two groups and predisposed to acute emotional stress. It was found that the contents of these peptides in Wistar-rats, which are more resistant to emotional stress, were higher compared with the August-rats, which are more predisposed to emotional stress. It was shown that the contents of beta-endorphin and DSIP in Wistar-rats is higher than in predisposed Wistar-rats.

[Delta sleep-inducing peptide in the blood and hypothalamus of rats with various resistance to emotional stress]. / Peptid, vyzyvaiushchii del'ta-son, v krovi i gipotalamuse u krys s razlichnoi ustoichivost'iu k émotsional'nomu stressu.

Enzyme immunoassay was used to study delta-sleep peptide content in blood and hypothalamus in rats of Wistar lines under acute emotional stress. It was found that the content of delta-sleep peptide in blood and hypothalamus of stable rats was higher as compared with rats predisposed to emotional stress. After 1.5-hour emotional stress the content of delta-sleep peptide increased in blood and hypothalamus both in stable rats and predisposed ones. After 3-hour stress there was an increase in delta-sleep peptide content in hypothalamus, and contrary to its decrease in blood in both stable and predisposed animals. It is supposed that delta-sleep peptide along with other oligopeptides is one of the factors determining individual animal resistance to emotional stress, which is supported by significant delta-sleep peptide increase in hypothalamus in stable rats.

[Self stimulation against a background of action of blockers of the synthesis of proteins and oligopeptides]. / Samostimuliatsiia na fone deistviia blokatorov sinteza belkov i oligopeptidov.

The experiments on rabbits have demonstrated that blockade of protein synthesis by the administration of cycloheximide and actinomycin D abolishes self-stimulation in the central nervous system. The treatment with ACTH fragment (ACTH4-10) restored the self-stimulation. Unlike ACTH, injections of pentagastrin, Met-enkephalin, Leu-enkephalin and cholecystokinin were ineffective. The present study shows that ACTH4-10 plays an important role in genetic determination of self-stimulation behaviour.