Voltage field effects on muscle fiber intracellular potential form

¹ Division of Physiology, Department of Biological Sciences, Florida State University, Tallahassee, Florida

Intracellularly recorded action potentials in narrow strips of frog m. adductor longus and sartorius were decreased as much as 40 mv when the external conducting volume was reduced by recording in oil. The decrease could be attributed to increased voltage effect from nearby active fibers. The field effect was simulated by means of external electrodes that provide, like the adjacent fibers, a pseudohyperpolarization during outward current through the impaled cell membrane. The typical end-plate spike form is considered to be mainly a result of field effects from nearby fiber impulses summing with the transmembrane potential of the impaled cell.