THE PHYSIOLOGICAL SIGNIFICANCE OF THE ELECTRIC RESPONSES OF SMOOTH MUSCLE

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Abstract
Mechanical and electric responses of the nictitating membrane and pllomotors of the cat were recorded on repetitive stimulation at various frequencies of the pre- and postganglionic nerve supply. The electrical excitability of the denervated nictitating membrane was studied. The effects of certain drugs on these phenomena were observed. The following conclusions are derived 1. the electrograms denote an asymmetric depolarization of oriented smooth muscle cells; 2. the polarity of the electrograms depends on the orientation of the muscles with respect to the electrodes; 3. therefore, the polarity of the electrograms of groups of cells does not give any information as to the sign of the elec- tric changes in the individual cells; 4. the electric potentials of neighboring cells may add in series; 5. the splke component (I) of the electrograms is probably produced by the chemical mediator; 6. therefore (I) is not a propagated disturbance; 7. it may not follow the all-or-none law; 8. smooth muscle may be electrically in-excitable; 9. the conclusions 6, 5, 7 and 8 reveal fundamental differences between smooth and skeletal muscle. The probable sequence of events in neuromuscular conduction in smooth muscles is summarized.

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