[A morphometric study of postnatal synaptogenesis in the neocortex of precocial and altricial rodents]

Quantitative electronmicroscopic studies have been made on the development of synapses in two modally different areas of the brain (V-VI layers of the visual and auditory cortex) in the rat and mouse Acomys cahirinus within first two weeks of their postnatal life. The density of synapses as well the relative amount of different types of synapses (symmetrical, asymmetrical, axo-spinal and synapses with large amounts of synaptic vesicles) were measured. It was shown that only in rats the development of synapses in the visual area usually is faster than in the auditory one.