The ultrastructure of the cat olfactory bulb.

Abstract

AbstractThe fine structure of the olfactory bulb was investigated in the cat. Five types of bulbar neurons were identified on the basis of size, location, cytoplasmic organelles and synaptic complexes with the neuron perikaryon. The smallest diameter neurons were predominatly located in the glomerular and granule cell layers. Ultrastructural characteristics for these two neuron populations, viz., periglomerular and internal granule cells, were identical. Tufted cells, smaller in diameter than mitral cells, were located in the external plexiform and glomerular layers and possessed all the morphological characteristics of the mitral cells. Mitral cells were the largest bulbar neurons and were located in a single lamina. Stellate (short‐axon) neurons were found in the glomerular, external plexiform and granule cell layers.Reciprocal synapses were observed in all laminae of the bulb except the primary olfactory nerve and deeper granule cell layers. Such synapses were found in the glomeruli, on tufted and mitral cells, in the neuropil of the external plexiform layer, and on the axon hillock and initial segments of the mitral cells. The morphology in the cat olfactory bulb corroborated bulbar ultrastructure described for other mammals.