MECHANISMS OF ACTION OF TRANSMITTERS AND OTHER SUBSTANCES ON SMOOTH-MUSCLE

This review is concerned with the mechanisms by which substances, many of them neurotransmitters, produce their effects on smooth muscle cells. It is concerned primarily with those that exert effects within seconds of their application to the muscle - effects most easily studied in vitro with the smooth muscle cells bathed in physiological salt solutions. Those substances, such as hormones or other trophic agents, that have a long-term effect are not considered here. An examination is presented of the strength of the experimental support for some simple concepts about how stimulant or inhibitory chemicals affect the contractility of smooth muscle. This review concentrates particularly on the effects of drugs, and substances found naturally in the body, on the permeability of the smooth muscle cell membrane and how these changes might increase or decrease tension in the contractile proteins.