Аннотация:Pulmonary arterial hypertension (PAH) is characterized by an increase of a pressure in thepulmonary circulation; PAH is accompanied by activation of the sympathetic (SNS) and the renin-angiotensin-aldosterone system (RAAS). However, PAH-associated changes in baroreceptor regulationof systemic circulation, which is tightly interwoven with SNS and RAAS, have not been studied. Thebaroreceptor response (BRR) was studied in a chronic monocrotaline (MCT) model of PAH in rats(Wistar, 290 ± 30 g, 2–4 months). Phenylephrine as an agonist of α1-adrenergic receptor and sodiumnitroprusside as NO donor were gradually administered to chronically catheterized, non-anesthetizedcontrol animals and animals with PAH (4 weeks after MCT administration) to induce vasomotorresponses. Mean arterial pressure and heart rate (HR) were recorded under the action of vasoactivecompounds alone or under the action of vasoactive compounds in presence of angiotensin-II (ATII),atropine. The parameters characterizing baroreceptor change in HR including maximal and minimalheart rate (HR max , HRmin ), reflex tachycardia (T BRR ) and bradycardia (B BRR ), range (A BRR ) and thebaroreceptor response sensitivity index (SI BRR) were calculated. A significant decrease in HR max , TBRR ,A BBR (but not B BRR ), as well as the sensitivity index of BRR was observed in rats with PAH. ATIIinduces significant and different changes in the BRR parameters in control rats and in rats with PAH ifadministered 4 weeks after the start of the experiment. In rats with PAH, ATII causes less pronouncedchanges in HR max, TBRR , and B BRR than in control animals. ATII insignificantly affectsparasympathetic component of the baroreceptor reflex in rats with PAH. Thus, at least in the MCT-mediated model in rats, PAH significantly deteriorates the baroreceptor regulation of HR. This effectmanifests in a decrease in the range and sensitivity of the baroreceptor response. Also, PAH unequallyaffects the sympathetic and parasympathetic control of the baroreceptor regulation of HR. On the otherhand, ATII exhibits weak ability to alter BRR in rats with HAP. In conclusion, PAH leads to adisfunction of immediate, reflex mechanisms HR and systemic circulation control.
