Accommodation and local response in motoneurons of toad's spinal cord.

Several investigations have been reported in recent years on the excitability of single nerve cells and the electrical properties of the neuronal membrane (Araki and Otani, 1955; Coombs, Eccles and Fatt, 1955; Frank and Fuortes, 1956; Coombs, Curtis and Eccles, 1957a, b; Ito, 1957). In those reports studies were made on the threshold depolarization produced by rectangular current pulses applied directly to the soma membrane. In some cases, there was found a gradual rise in the threshold depolarization with the increase in the latent period and references were made to its possible relationship with accommodation in the neuronal membrane (Araki and Otani, 1955; Frank and Fuortes, 1956; Coombs et al., 1957 b). However, no systematic research has been reported on accommodation in nerve cells, which will be explored only with slowly rising currents delivered as direct stimulation. In the present paper, responses of toad's spinal motoneurons to exponentially increasing currents will be described. Thus the main problem treated here is accommodation in the motoneurons, but reference will be made also to some minor experiments as to the nature of local response and a paradoxical state of the synaptic transmission, i.e., Wedenski inhibition.