Morphology of afferent and efferent synapses in hearing organ of goldfish

The sacculus, the hearing organ, of the goldfish was fixed with three different kinds of fixatives: osmium tetroxide, glutaraldehyde and formaldehyde. Three kinds of synapses are encountered in the sensory epithelium: the synapse between the hair cell and the afferent nerve ending, the synapse between the efferent nerve ending and the hair cell, and the synapse between the hair cell and the afferent nerve ending, there are synaptic vesicles about 370-430 A in average diameter in the hair cell side of the junction. The vesicles are always round in dependent of the fixative used. In the other two kinds of synapses, the efferent ending contains smaller vesicles about 310-360 A in average diameter. The shape of the vesicles changes according to the fixative used; round in osmium tetroxide-fixed materials, and elongated in aldehydefixed materials. The synapse between the hair cell and the afferent nerve ending in excitatory in nature, while the other two types of synapses are thought to be inhibitory in nature.