Relative distribution densities of cholinergic and adrenoceptor structures in the central part of the sinoatrial node in rat heart.

Characteristics of distribution of cholinergic and adrenoceptor structures along the sinoatrial node artery in rat heart were evaluated by autoradiography on semithin sections by determining the density of (3)H-dihydroalprenolol and (3)H-quinuclidinyl benzilate binding sites. The relative density of binding sites for (3)H-dihydroalprenolol and (3)H-quinuclidinyl benzilate was minimum in the functional nucleus of the sinoatrial node and asymmetrically increased to maximum values to cranial (sharply) and caudal (smoothly) directions. The relative level of binding for (3)H-dihydroalprenolol in the perinodal atrial myocardium tissue was markedly lower than in the periarterial zone of the central part of the sinoatrial node and comparable to that for (3)H-quinuclidinyl benzilate.