title: The ultrastructural organization of lamina VI of the spinal cord of the cat. Morphological characterization of the synaptic population.
abstract: The synaptic population of lamina VI of the cervical enlargement of the cat spinal cord has been studied analysing 9 different morphological features and determining the incidence of possible combinations. The most important factors to characterize the synaptic boutons were the shape and size of pre-synaptic vesicles and the size of the synaptic boutons. The incidence of features like the density of the synaptic vesicles, the characteristics of the synaptic junction, the occurrence of post-synaptic specializations, the fibrillar or glycogen content of the pre-synaptic bag and the presence of dense-core vesicles, was unimportant. Most of the boutons (69%) contain pleomorphic vesicles (P boutons), 22% round vesicles (R boutons) and 9% flattened vesicles (F boutons). These synaptic types were further subdivided on the basis of the size of their synaptic vesicles. Most of the synapses (84%) were symmetrical, without relation to the shape of the pre-synaptic vesicles. Dense-core vesicles were found in 15% of the synaptic boutons and occurred most frequently in R boutons. On the basis of the analysis performed, we propose to classify synaptic boutons of lamina VI in 13 different types.
mesh_terms: D000818:Animals; D002415:Cats; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D006003:Glycogen / Q000378:metabolism; D008854:Microscopy, Electron; D013116:Spinal Cord / Q000378:metabolism / Q000648:ultrastructure*; D013569:Synapses / Q000648:ultrastructure; D013572:Synaptic Vesicles / Q000648:ultrastructure
chemical_list: D006003:Glycogen