[Changes in the NO-dependent regulation of the local cerebral blood flow in rats during adaptation to the conditions of simulated weightlessness].

The nitrogen oxide NO-dependent regulation of the cerebral blood flow was studied before and after 24-hr head-down immobilization (HDI) of intact and pre-trained rats. Training consisted in 2-hr tail-suspension each day of the 2-wk period. Blood flow was determined with the laser Doppler flowmetry following local injection of a NO synthesis blocker (L-NAME), and NO (sodium nitroprusside).

[Atropine effect on physostigmine- and stress-induced secretion of catecholamines by adrenal gland: microdialysis study in awake rats].

Physostigmine and an 1-hour immobilisation stress similarly affected functions of the sympatho-adrenal and cardiovascular systems activating the catecholamine secretion and increasing the blood pressure. Yohimbine potentiated the secretory effect but did not change the pressor effect. Intermediate administration of atropine completely eliminated both effects of physostigmine but, being administered prior to the immobilisation, it potentiated the secretory response without affecting the pressor response.

[Chronic stress increases the reactivity of central depressor mechanisms].

The activity of noradrenergic system of lateral hypothalamus and hemodynamics were studied during acute restraint in chronically stressed and control rats. Arterial blood pressure in rest was negatively proportional to basal norepinephrine concentration in dialysate of lateral hypothalamus. Animals with high increase of norepinephrine levels in dialysate during acute stress had rapid return of arterial blood pressure to basal values while stress-induced hypertension in the beginning of restraint was the same as in rats with low increase of norepinephrine levels.

[The activity of the monoaminergic systems of the rat hypothalamus in acute stress after chronic stressing].

The influence of chronic stress (footshock combined with randomized light flashes) on acute stress-induced (immobilization) release of noradrenaline, dopamine and serotonin in rat lateral hypothalamus was assessed by microdialysis. The chronic stress resulted in an increase and prolongation of the acute stress-induced release of noradrenaline but not of dopamine and serotonin. The increased rate of accumulation of dioxyphenylacetic acid and unchanged accumulation of homovanillic acid (dopamine metabolites) and dopamine during and after the acute stress in chronically stressed animals reflect a rise of synthetic activity of catecholaminergic systems in response to acute stress and reuptake increase.

[Changes in the local cerebral blood flow during the microdialysis administration of vasoactive substances].

The authors suggest the construction of a cannula for microdialysis combined with a light guide of a laser doppler flowmeter. Such a design allows monitoring of blood flow intensity in the environment of the microdialyzer. An advantage of local administration of vasoactive agents is that they cause no effect on systemic arterial pressure.