[The hypothalamic mechanisms of the development of arterial hypertension in old age].

The electrical activity of hypothalamic nuclei was found to change in accordance with changes in arterial blood pressure in old rabbits with reflexogenic hypertension. Stimulation of the hypothalamus induced an obvious increase in the blood pressure, considerable changes in cardiac activity, coronary insufficiency occurrence and alteration of the myocardium structure. An increase in excitability of the pressor structures of the anterior and posterior hypothalamic areas occurred with ageing.

[Regulation of corticoliberin and corticotropin incretion in old age].

Experiments on adult and old rats have shown age-related decrease of the CRF incretion in the hypothalamus, weakening of its response to dexamethasone, as well as a decrease of receptor corticosterone binding. Against this background in the hypophysis of old rats sensitivity ox CRF and serotonin increased, in stress the same content of ACTH as in adult rats secreted, it more markedly reacted to dexamethasone, and receptor of corticosterone binding increased in hypophysis. In old age, the role of hypophyseal link in control of the adrenocortical function is assumed to increase in stress.

[The system of regulation of aldosterone secretion in old rats].

The experiments performed on mature (4-6) and old (28-30 months) rats revealed changes developed in old animals in various links of regulatory system of aldosterone secretion: the decreased hypothalamohypophyseal control of mineralocorticoid secretion, increased sensitivity of glomerular zone to ACTH, vasopressin, K+ and of myocardium skeletal muscle and renal tissue to aldosterone. Changes in tissue sensitivity to aldosterone may be conditioned by the increased affinity of mineralocorticoid receptors to aldosterone in old age.

[Effect of acetylcholine on protein biosynthesis in regions of the heart in adult and old rats].

Effect of acetylcholine on incorporation of labelled amino acids (14C hydrolysate of chlorella protein) into the free amino acid pool and total protein was studied using slices of auricles, right and left heart ventricles, obtained from 2-month, 8--10 month and 26--28-month old rats. Changes in the intensity of protein biosynthesis were estimated by following relative specific activity (RSA--protein specific activity/free amino acid pool specific activity). Maximal increase in the RSA value was found: in auricles of 2-month old rats in presence of 2.

[Role of protein biosynthesis activation in the mechanism of the negative chronotropic action of the vagus nerve and acetylcholine on the heart].

In rats, the following data were obtained: a) acetylcholine activates the rate of protein biosynthesis in auricles in vitro; b) protein biosynthesis inhibitors (actinomycine D, sarcolysine, neutral rot, tolluidine blue) weaken the negative chronotropic effect of acetylcholine and vagus on the heart; c) anabolic hormones increase the cholinergic effect on heart; d) acetylcholine induces hyperpolarization of the myocardial fibers which is prevented by actinomycine D. The activation of protein biosynthesis followed by hyperpolarization of the pacemaker cells seems to play an important role in the mechanism of negative chronotropic effect of acetylcholine and vagus on the heart.

[Nervous regulation of cardiac function during aging].

The hemodynamic changes and myocardium contractile capacity following the extracardiac nerves stimulation with acetylcholine, norepinephrine, inderal, regitin and atropine, as well as the activity of main enzymes of cholinergic and adrenergic metabolism, were studied in albino rats, rabbits, and cats of various age. With ageing, the thresholds of vagal and sympathetic nerves influences on the heart increased, the sensitivity of heart to acetylcholine and norepinephrine changed. In old animals, smaller atropine and in deral doses blocked the respective cholinergic and beta-adrenergic reactions.

[Catecholamine concentration and metabolism in old age].

As shown by examination in apparently healthy persons aged from 20 to 100 years and in experiments on 1--28-month-old albino rats there was a significant change with the progress of age in the content and ratio of catecholamines in the blood, various organs and the urine. The blood noradrenaline level fell considerably; Na/A coefficient also dropped sharply. Catecholamine content in the organs changed irregularly: in the kidneys it increased, in the skeletal muscles--remained unchanged, in the adrenal glands, the heart, the spleen and the liver--decreased.