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Biomedical subjects

A A Filaretov

Publications and source records attributed to A A Filaretov.

18 recordsLinked to original sources
PubMed1992

[The effect of large doses of corticosteroids on stomach ulcer formation: a new hypothesis].

A new hypothesis is suggested according to which the ulcerogenic effect of large corticosteroid doses is regarded as a consequence of suppression of hypothalamo-pituitary-adrenocortical system (HPAS) function. On the 7-th day after the administration of a large hydrocortisone dose to rats the HPAS block was observed. The HPAS block increased the area of hemorrhagic damages of the stomach mucosa induced by a stress factor. Similar data on the ulcer formation were obtained when using intrahypothalamic administration of dexamethasone. The replacement therapy decreased the effect of HPAS block in both cases. The data show that the stomach ulcer formation after the administration of high corticosteroid doses occurs as a result of endogenous hormone production insufficiency.

Adrenal Cortex Hormones↗
PubMed1992

[The importance of the adrenals in altering the properties of the hypothalamo-hypophyseal-adrenocortical system after stress].

The effect of stress on adrenal response to ACTH was studied in vivo and in vitro in rats. There were a decrease of capacity and an increase of responsiveness to ACTH of adrenals from rats which were exposed to electrical stimulation of foot. The date explain the mechanisms of hypothalamo-pituitary-adrenocortical system changes in total after stress which was obtained in our previous work.

Adrenal Cortex↗
PubMed1991

[The central gray substance of the midbrain: the role of corticosteroids in the analgesic effect].

The effect of stimulation of periaqueductal gray matter on pain threshold and blood corticosteroids was studied in anesthetized rats. The stimulation with 30-50-microA current resulted in an increase of analgesia and blood corticosteroids. An increase of current intensity up to 100 microA resulted in a decreasing corticosteroid level and analgetic effect. The magnitude and duration of the analgesia were decreased after blocking the pituitary-adrenocortical system. The corticosteroids seem to induce analgesia after stimulation of periaqueductal gray matter stimulation.

Adrenal Cortex Hormones↗
PubMed1990

[Patterns in the functioning of the hypophyseal-adrenal cortical system during repeated stress stimuli].

The dependence of pituitary-adrenocortical system (PACS) response on the strength of electrical skin stimulation was investigated in alert rats. Changes in the PACS responses did not depend on the first stressful stimulation but became more obvious in an increased stimulation. Responses to subsequent stimulations were equal or more obvious than the response to the first weak stimulus, whereas the responses to repeated stimuli were smaller than the first one if the first stimulus was strong.

Adrenal Cortex Hormones↗
PubMed1988

[Role of the hypophysis and hypothalamus in the control of feedback of the hypophyseal-adrenocortical system].

The role of hypophysis and paraventricular hypothalamic nucleus in inhibition of pituitary-adrenocortical system induced with hydrocortisone in increasing doses (100, 300, 1200 mg/100 g b. w.) was studied in rats. The ACTH secretion induced with pituitrin was only decreased after administration of 1200 mg/100 g b. w. of hydrocortisone, whereas smaller doses did not alter the responsiveness of hypophysis. After lesion of the paraventricular hypothalamic nucleus the inhibition of the stress-induced reaction of pituitary-adrenocortical system was either eliminated or decreased depending on the dose of hydrocortisone administered. The inhibition induced with hydrocortisone in physiological doses seems to depend on the hypothalamus. However, both the hypothalamus and the hypophysis take part in an inhibition induced with supraphysiological doses of the hormone.

Adrenocorticotropic Hormone↗
PubMed1978

Electrical activity of hypothalamus during activation of pituitary-adrenocortical system.

Multiunit activity in anterior (AHA), medial (MHA) and lateral (LHA) areas of hypothalamus during activation of the pituitary-adrenocortical system was measured in chronic experiments on rabbits. Immobilization causing blood-corticosteroid levels to rise was followed by the excitation of most pools of neurons in MHA, and by inhibition in AHA and LHA. When immobilization failed to induce stimulation of MHA (as a result of pretreatment with large doses of cortisol), it did not cause blood-corticosteroid levels to rise, either. The switching off activity in AHA and MHA is considered to be a manifestation of functional changes which are responsible for stress-induced activation of the adrenocortical system.

Adrenal Cortex Hormones↗
PubMed1977

[Role of the medial hypothalamus in regulating the pituitary-adrenocortical system].

In unrestrained rabbits, inhibition of ACTH release as determined by changes in plasma levels of corticosteroids, followed electrolytic lesion of the dorso-and ventromedia nuclei of the hypothalamus. Electric stimulation of the dorsal midbrain tegmentum had activated ACTH prior to lesion; after the lesion of the dorso-and ventromedial nuclei the stimulation produced no response. The dorso-and ventromedial nuclei of the hypothalamus are essential for basal and induced secretion of the ACTH.

Adrenal Cortex Hormones↗
PubMed1977

[Electrical activity of the hypothalamus during stress].

Chronic experiments were undertaken on rabbits to ascertain the multiunit activity of the anterior (AHA), medial (MHA), and lateral (LHA) hypothalamic areas during the immobilization stress. The immobilization excited the adrenocortical activity and changed the multiunit activity. The stress resulted in a decrease in the firing rate in most pools in the AHA and LHA, and an increase in the MHA.

Animals↗
PubMed1977

[Projections of the posterior region of the hypothalamus into its medial, anterior and lateral region].

Effect of stimulation of the lateral and medial supramammillary areas of the hypothalamus was studied in acute experiments on rabbits. The firing of neurons was recorded in the anterior, lateral, dorsal medial and ventral medial hypothalamic areas. Single pulse stimulation of the medial area of the posterior hypothalamus caused changes in discharge rate for 44% of neurons and the stimulation of the lateral area for 35% of the examined neurons. Repetitive stimulation resulted in changes of the discharge rate in 57% of neurons during stimulation of the lateral and in 74% of the medial supramammillary area. Most neurons responded by excitation. The data obtained are discussed from the view point of the role of posterior hypothalamus in the regulation of the adenohypophysis functions.

Animals↗
PubMed1977

[Participation of the hypothalamus in regulation of the pituitary-adrenal system in accordance with the feedback principle].

The multiunit activity and activity of pituitary-adrenocortical system were studied in chronic experiments on intact unrestrained rabbits injected with cortisol (1 mg/kg, i.v.). The pituitary-adrenocortical system was inhibited by cortisol (the level of corticosterone decreased) as well as the majority of the neuronal pools in the medial and lateral hypothalamus. The anterior hypothalamic neurons mostly responded to cortisol by a rise in firing rate. The changes observed suggest the existence of some electrophysiological correlates of the corticosteroid feedback mechanisms.

Animals↗
PubMed1976

The afferent input and functional organization of the hypothalamus in reactions regulating pituitary-adreno-cortical activity.

In chronic experiments on rabbits, stimulation of the dorsal tegmentum of the midbrain caused an increase in serum corticosteroid level. In acute experiments, stimulation of the same region resulted in changes in the activity of hypothalamic neurons. Neurons in the anterior (AHA), medial (MHA), including the medial dorsal (MHAd) and medial ventral (MHAv) areas, and lateral (LHA) areas of the hypothalamus were studied. When the midbrain was stimulated, more neurons in LHA, MHAd and MHAv were excited than inhibited; in AHA, more neurons were inhibited. These changes suggest that the activation of the pituitary-adrenocortical system caused by stimulation of the dorsal tegmentum is associated with changes in the influx of afferent impulses to the hypothalamus, which are responsible for AHA inhibition and MHA and LHA excitation.

Afferent Pathways↗
PubMedDate not supplied

Patterns of the functioning of the hypophyseoadrenocortical system in the presence of repeated stressful stimulations.

The relationship of the magnitude of the response of the hypophyseoadrenocortical system (HACS) to the strength of the stimulus in the presence of isolated or repeated stressor influences was determined in experiments on awake rats. Electrical stimulation of 0.1-0.9 mA of the skin of the paws for 3 min served as the stimulus. The reaction of HACS was judged on the basis of the determination of blood corticosteroids. Changes take place in the physiological characteristics of the system 30 mins after the termination of the stressor activation of the HACS. These changes do not depend on the strength of the initial stressor, and consist of a decrease in the threshold of excitability and a reduction in the maximum of the reaction to stressors of greater strength. The reaction to repeated stimulation at small strengths of the initial stressor proved to be larger or equal to the response of the system to the initial stimulation. At greater strengths of the stressor the reaction to repeated stimulation is significantly less than to the initial stimulation.

Adrenal Cortex↗