Adrenergic Regulation of the Functioning of the Cardiovascular System under Hypothermic Conditions

Regulation of the function of the cardiovascular system under and after hypothermia is one of important and relevant tasks in biomedical research. It is because of both – serious complications of hypothermia and the potential outcome benefits with hypothermia used for medicinal purposes. Adrenergic regulation is central for the normal function of the cardiovascular system. There are three types of adrenergic receptors known as α1, α2 and β, the expression levels of which are different in the myocardium and blood vessels. Activation of each of the adrenergic receptor subtypes can cause differently directed effects, which are significantly modified under the conditions of low temperature. The effectiveness of β-adrenergic stimulation decreases and β-adrenergic stimulation can even act like hypothermia, leading to impairment of myocardial function. The severity of the effects of α1 adrenergic agonists both on myocardial tissue and in blood vessels is also diminished, however, sensitivity to stimulation of α1a receptors in blood vessels may increase. The activation of α1 adrenergic receptors mediates protective effect in the heart. The activation of α2 adrenergic receptors has a fairly wide range of protective effects on the heart. However, there is now increasing evidence of direct inotropic and vascular effects mediated by this type of receptor. There is also some evidence that these effects become more pronounced under hypothermia. This review examines the current state of research on the effects of stimulation of certain types of adrenergic receptors under normal and hypothermic conditions, analyzes the mechanisms of physiological action and prospects for their further research.