Lack of effect of receptor blockers on the formation of long-lasting associations between sympathetic nerves and cardiac muscle cells in vitro.

Sympathetic nerves in vitro form long-lasting, intimate, functional relationships with cardiac muscle cells, but not with fibroblasts. In the presence of an adrenergic beta-blocker and a cholinergic muscarinic blocker, long-lasting relationships still take place. It was concluded that neurotransmitter "receptors" are not involved in the mechanism of "recognition" of cardiac muscle cells by sympathetic nerves.