Alpha2-adrenergic receptors of myocardium (review)

The review deals with alfa2-adrenoreceptors (АR) of the myocardium of humans and animals. Data on 4 subtypes of these receptors (A, B, C, and D) and the role of alfa2-АR as presynaptic autoreceptors in terminal sympathetic nerves are presented. It is reported that activation of alfa2-АR, as a rule, is accompanied by the development of negative inotropic and chronotropic effects. This activation also prevents the development of myocardial hypertrophy and other disorders in cardiac performance. All these effects, including cardioprotective ones, indicate that the given type of receptors carries out the function of autoreceptors. Data on the mechanisms underlying all specified effects are given. It is most probable that these mechanisms are related with inhibition of adenylate cyclase (with Gi-protein participation) and activation of protein kinase C (with Gq-protein participation). The role of alfa2-АR in development of negative inotropic effect of adrenaline against the background of blockade of beta1- and beta2- АR is considered.