Modulation of smooth muscle activity by catecholamines
Marshall, J.M.
Federation Proceedings 36(10): 2450-2455
1977
ISSN/ISBN: 0014-9446 PMID: 196944 Document Number: 119436
The inhibitory and excitatory actions of catecholamines are compared in various types of smooth muscle. Inhibition is usually but not invariably associated with membrane hyperpolarization and a decrease in membrane resistance. It also has a metabolic component frequently involving an increase in tissue cAMP. In some cases, the metabolic component is related to a cation pump, but the nature of this pump is unclear. With the exception of intestinal muscle where inhibition results from the synergistic action of alpha and beta receptors, inhibition is caused by activation of beta receptors. Excitation is mediated by alpha activation and is usually accompanied by a decrease in membrane potential and membrane resistance. Only the uterus has a metabolic component. The specific ionic permeability changes accompanying excitation are different in various smooth muscles. Clarification of the mechanisms responsible for these differential actions in various types of smooth muscle is a challenge for future work.