Neuroendocrine mechanisms of hypertensive states developing during chronic emotional stress.

This paper discusses central neuroendocrine mechanisms involved in the development of hypertensive states during emotional stress with reference to the data published in the literature and obtained by the author. The experimental results are used to identify the structural and functional organization of the central nervous system that provides integration of nervous and hormonal factors in the pathogenesis of hypertensive states in response to emotional stress. The hypothesis about the trigger role of posterior hypothalamic nuclei which activate neuroendocrine mechanisms of the development of hypertensive states during emotional stress is documented. Mechanisms of MBRF's participation in the realization of emotional stress are clarified.

[Neuroendocrine mechanisms of participation of the raphe nuclei in the development of hypertensive reactions in emotional stress]. / Neiroéndokrinnye mekhanizmy uchastiia iader shva mozga v razvitii gipertenzivyykh reaktsii pri émotsional'nom stresse.

The experiments on cats and rabbits have studied electroencephalographic, endocrine and blood pressure responses to stress (5-hour immobilization with electrical foot shock) before and after coagulation of the midbrain nuclei raphe. Blood pressure and adrenal responses in advanced (4-hour) stress were elevated in intact animals, the responses attenuating after coagulation of the nuclei raphe. Background bioelectrical activity of the midbrain reticular formation and hypothalamus was found to be activated in the operated animals. Stress was followed by the reduction in bioelectrical changes of the above subcortical structures with the parallel development of "burst" activity in the dorsal hippocamp.

Neurophysiological analysis of the development of endocrine and hypertensive reactions in prolonged emotional stress.

The model of immobilization stress with aperiodic foot shock (FS) was used to study the effect of a prolonged emotional stress on the functional condition of cortical and subcortical structures (hypothalamic and reticular structures in particular) in EEG activity and to elucidate their role in the development of endocrine and hypertensive reactions. It is shown that the development of hypertensive reactions in animals is stipulated by dynamic changes in the functional condition of the CNS, particularly in the hypothalamic neuroendocrinal control mechanism and reticular formation of the midbrain, which can be conditionally subdivided into 3 stages. The first is characterized by the emergence of short-time cycles of the hypersynchronized activity of slow waves in the cortical and subcortical mechanism, which is accompanied by adaptive hormonal secretion and transient effects of vascular reactions to FS; in the meantime neither neuroendocrinal nor blood pressure (BP) self-regulation mechanisms are impaired. The second stage is characterized (3-4 days after the beginning of the exposure) by the development of 'persistent' excitation in the CNS and the stabilization of a high level of hormones in the blood. Vascular reactions to FS are extremely prolonged ones; in intervals between FS applications BP fails to return to initial values. The third stage (1 month after cessation of experiments) is characterized by normal background EEG-activity in cortical-subcortical structures, normal indices of hormonal homeostasis but high level of BP. In response to 'repeated' stress, on the first experimental day, prolonged hypersynchronization of slow waves in cortical-subcortical structures occurred while BP reactions to FS were also prolonged and high hormonal secretion was observed. The data obtained suggest the high reactivity of reticular-hypothalamic structures which determine primarily the characteristics of both vascular and hormonal reactions that could be understood to be due to the result of previous experience (the first stage of stress).

[ACTH, corticosterone and beta-endorphin in the blood plasma of rats under prolonged immobilization stress]. / AKTG, kortikosteron i beta-éndorfin v plazme krovi krys v usloviiakh dlitel'nogo immobilizovannogo stressa.

Radioimmunoassays were employed to study variation in the concentration of corticosterone, ACTH and beta-endorphin in rat blood plasma at different times of the 30-hour immobilization and under the effect of a short-term action of ecologically significant negative stimulation emanating from other animals. Both prolonged immobilization stress and short-term emotional reaction produced appreciable alterations in the blood plasma content of all the hormones under study. The findings indicate that variations in the corticosterone and beta-endorphin levels were in the best agreement.

[Neurophysiological analysis of the development of endocrine and hypertensive reactions in long-term emotional stress]. / Neirofiziologicheski analiz formirovaniia éndokrinnykh i gipertenzivnykh reaktsii pri dlitel'nom émotsional'nom napriazhenii.

A study was made of the effect of chronic emotional stress on the formation of hypertension in animals. This was shown to be related to dynamic changes in the function of the CNS, particularly in the hypothalamic apparatus of the neuroendocrine control. The above changes played a role in the formation of hypertensive vascular reactions accompanied by a high hormonal secretion of the adrenal cortex and thyroid. During stabilization of high arterial blood pressure at the late stages of the "after-effect", the hormonal secretion returns to normal.

[Role of the midbrain reticular formation in hormonal supply to the body in conditions of chronic emotional stress]. / Rol' retikuliarnoi formatsii srednego mozga v gormonal'nom obespechenii organizma v usloviiakh khronicheskogo émotsional'nogo napriazheniia.

Chronic animal experiments were made to study the endocrine and electroencephalographic responses of the cortico-subcortical structures to stress before and after coagulation of the midbrain reticular formation. The operation entailed dramatic changes in both the bioelectrical responses and thyroid and adrenal responses, which were found to be differentiated.

[Neuronal responses of the intact cortex and isolated strips of the sensorimotor cortex to systemic administration of thyroxine]. / Reaktsiia neironov intaktnoi kory i neironal'no izolirovannoi poloski sensomotornoi kory na sistemnoe vvedenie tiroksina.

The pattern of neuronal responses to alterations in hormonal homeostasis was specified. A study was made of neuronal responses of intact and neuronally isolated strips of the sensorimotor cortex (ISC) to intravenous injection of thyroxine. The neuronal response of the ISC was found to differ substantially from the response of intact cortical neurons. Less percentage of the responding neurons was registered in the ISC. The responses were considerably shortened, while the neurons discharged at a lower frequency. The differences indicate that, as compared to subcortical structures, the cortical neurons are less susceptible to blood hormones. It is emphasized that subcortical structures, particularly the hypothalamus are of major importance for transmission of hormonal influences to the brain cortex.

[Correlations of central nervous system and thyroid function under chronic emotional stress]. / Korreliatsionnye otnosheniia funktsional'nogo sostoianiia tsentral'noi nervnoi sistemy i shchitovidnoi zhelezy v usloviiakh khronicheskogo émotsional'nogo stressa.

Experiments on cats exposed to chronic emotional stress induced during one week by 4-hour immobilization of the animals in conjunction with aperiodic electrocutaneous stimulation were made to study correlations of the time course of changes in the EEG of the cortical and subcortical structures and the content of thyroxin in the peripheral blood at varying time of the experiments. It was demonstrated that in the course of stress, the EEG manifests the cycles of "burst" activity of slow waves, which are first recorded in the posterior hypothalamus and then get generalized. This is accompanied by a significantly high thyroxin secretion. As the stress exposures are repeated, the EEG changes become dominant, also corresponding with high thyroxin secretion. After the experiments are over, the cycles of "burst" activity accompanied by enhanced thyroid function are still recordable over several days.

[Dynamics of hormone secretion during chronic emotional stress]. / Dinamika sekretsii nekotorykh gormonov pri khronicheskom émotsional'nom napriazhenii.

Study of spontaneous secretion of corticosteroids and thyroid hormones and the direct hormonal response to stress revealed the pathogenic effect of chronic combined emotional stress upon the hormonal function of adrenal glands. The hippocampus takes part in formation of the emotional tension in response to stress stimulus and of the following hormonal secretion.

[Participation of the amygdaloid complex in the regulation of insulin and corticoid secretion in emotional stress]. / Uchastie mindalevidnogo kompleksa v reguliatsii sekretsii insulina i kortikoidov pri émotsional'nom stresse.

The emotional stress induced in dogs by means of electrodermal stimulation, lowered the blood insulin and increased the corticoids and sugar contents. Bilateral amygdalectomy eliminated the inhibitory effect of the electrodermal stimulation on the insular apparatus and caused a lesser albeit prolonged increase in the blood corticoid content. The blood sugar under these conditions was also somewhat increased. Different effects of separate amygdaloid nuclei on insulin secretion were revealed in acute experiments. The inhibitory effect of amygdaloid nuclei is realised through ventromedial hypothalamic nucleus

[Mechanism of the effect of the midbrain reticular formation on the hypothalamus-hypophysis-thyroid gland system]. / Mekhanizm vliianiia retikuliarnoi formatsii srednego mozga na sistemu gipotalamus-gipofiz-shchitovidnaia zheleza

The role of the posterior hypothalamic nuclei in the transmission of the influences of the mesencephalic reticular formation upon the thyroid hormone secretion was studied. Stimulation of the mesencephalic reticular formation in anesthetized cats was followed by the excitation of the thyroid hormoone secretion: the content of the blood protein-bound iodine was increased. This effect was eliminated after the bilateral coagulation of the posterior hypothalamic nuclei. These findings confirmed the hypothesis on the leading role of the posterior hypothalamic nuclpeus in the stimulation of the hormone secretion.

[The role of the posterior hypothalamic nucleus in thyroid hormone secretion during defensive conditioned reflex activity]. / Rol' zadnego gipotalamicheskogo iadra v sekretsii tireoidnykh gormonov pri oboronitel'noi uslovnoreflektornoi deiatel'nosti

In chronic experiments on adult rabbits, the EEG revealed participation of the posterior hypothalamic nucleus and mediobasal hypothalamus in conditioned avoidance response. Secretion of the thyroid hormone was increased during the response in intact dogs. This reaction of the thyroid gland was maintained for several months. After coagulation of the posterior hypothalamic nucleus the reaction disappeared. This suggests a triggering role of the posterior hypothalamic nucleus in secretion of the thyroid hormone during the avoidance response.

[The role of the reticular formation at the hypothalamic level in regulating insulin secretion]. / Rol' retikuliarnoi formatisii gipotalamicheskogo urovnia v reguliatsii sekretsii insulina

In cats, electric stimulation of direct microapplication of insulin to posterior hypothalamic nucleus increases the insulin content in the pancreatic venous blood independently of the concomitant changes of the blood sugar level. The insulin had no such effect in bilateral lesion of the lateral hypothalamus. Blockade of M-cholinergic system did not influence the changes of blood sugar level in these conditions. Electric stimulation of the anterior hypothalamic nucleus entailed no obvious changes of insulin and sugar level in the blood.

[Mechanisms of central regulation of blood sugar content]. / O mekhanizmakhanizmakh tsentral' noi reguliatsii soderzhaniia sakhara v krovi

Acute experiments were conducted on adult cats. Injection of insulin microdose (0.025 U/kg with 0.025 ml of saline) into the posterior hypothalamic nucleus caused an increase in the blood sugar level 10 and 70 min after the injection. Changes of the blood sugar level correlated with the EEG activation of the posterior hypothalamic nucleus in response to the insulin injection, spreading to the lateral hypothalamus. However, hormonal stimulation of the posterior hypothalamic nucleus against the background of bilateral coagulation of the lateral hypothalamus produced no increase in the blood sugar level in 10 min. This is indicative of the participation of the lateral hypothalamus in the realization of hyperglycemic reactions in response to the insulin injection into the posterior hypothalamic nucleus.