Shapes and sizes of synaptic vesicles in the cerebellum of the Syrian hamster‐cortex and deep nuclei

Abstract

AbstractMaterial was obtained from eight adult apparently healthy Syrian hamsters perfused with 3.2% glutaraldehyde in phosphate buffer. Cortex and deep nuclei were prepared for electron microscopy by osmication and Epon embedding. Measurement of size and shape of vesicles was from printx × 50,000. Vesicle profiles whose least diameter was 75% or more of the maximum diameter were classified as round (spherical). If the greatest dimension was more than twice the least, the vesicle was termed flattened, all others oval. So defined, the synaptic sacs in the deep nuclei, large sacs of the granular layer and small sacs of the molecular layer contained more round vesicles than oval and flat combined and differences between these three locations were slight. In large sacs of the molecular layer, oval and flattened vesicles slightly outnumbered round ones. Average sizes were deep nuclei 468 Å, large sacs of granular layer 494 Å, small sacs of molecular layer 452 Å and large sacs of molecular layer 414 Å. Statistical analysis indicated that the mean size of vesicles was significantly different when each of the four locations was compared with the others. These differences are too small to be apparent by inspection. Since the vesicles in the deep nuclei are intermediate in size between those in mossy terminals and the axospinous ones of the molecular layer it was concluded that size and shape of vesicles did not distinguish between excitatory and inhibitory synapses in Syrian hamster cerebellum.