"ELECTRICAL TRANSMISSION" AT AN EXCITATORY SYNAPSE IN A VERTEBRATE BRAIN.

A type of excitatory synaptic transmission which is novel for the vertebrate brain has been found in the ner neuron (M-cell) by means of the passive spread of their action currents across the synaptic membrane. After stimulating the ipsilateral eighth cranial nerve, an excitatory postsynaptic potential (EPSP) appears in the M-cell with a latency which is very brief ( about 0.1 msec) and which proba; bly represents a negligible synaptic delay. This response is attributed to the club endings: there were steep gradients of potential along the lateral dendrite of the M-cell during activity and the early EPSP was maximal in the distal part of the dendrite where the club endings predominate. Potential changes in the M-cell spread (passively) backwards into certain eighth-nerve fibers (probably club endings) indicating the presence of special low-resistance connections between them and the M-cell.