Repetitive discharges in mammalian striated muscle fibres evoked by a local current

Summary Some of the properties of a single mammalian straited muscle fibre were studied by applying a local depolarizing or hyperpolarizing current.During a long lasting depolarizing current of more than 0.05 A or after termination of a hyperpolarizing current of about 0.5 A a burst of spikes was evoked.The time intervalls between the action potentials got progressively longer with the time after onset of the positive current pulse or after termination of the negative current.Not only the stimulus current-time interval relation appears to be logarithmic for both stimulus polarities but also the stimulus duration-time interval relation with negative stimulation.The change in the time intervals between successive action potentials during a positive current is much slower than after a hyperpolarizing negative current.It is suggested that the increase in the time intervals between the action potentials evoked during a depolarizing stimulus is related to accommodation of the fibre and that the change in the time intervals after a hyperpolarizing stimulus is due to the fibre accommodation and to the recovery of the fibre after a partial breakdown of the membrane.