EXCITATORY AND INHIBITORY SYNAPSES IN THE CAT SPINAL CORD

Abstract

New fixation methods in electron microscopy using formalin have revealed that there are two different types of synapses in the anterior horn of the cat spinal cord. The one type of synapse contains vesicles of spherical shape A of about 500Å diameter, while the other synapse contains ellipsoidal vesicles. of the smaller size than the former. In comparison with Purkinje cells in the cat's cerebellum which have been identified as having excitatory (spherical) and inhibitory (ellipsoidal) synapses on the dendrite and soma of neuron respectively, it may be concluded that the motoneuron of the cat's anterior horn has two types of synapses, of which one contains excitatory synaptic vesicles (spherical) and the other contains inhibitory synaptic vesicles (ellipsoidal).