Freeze-etching study of synaptosomes from rat cerebral cortex

Synaptic membrane morphology in the rat cerebral cortex during development: image analysis of freeze-etching replicas of isolated synapses and synapses in situ

Both synaptic sites in situ from rat cerebral cortex and isolated ones in synaptosomal and growth cone fractions derived from it were studied during postnatal development. Freeze-etching technique and image analysis were used to determine the size of the intramembranous particles in the pre- and postsynaptic sites. At each age investigated, the greatest mean particle size was established on the E-face of the postsynaptic sites and ranges from 6.2 nm (day 0) to nearly 10 nm (day 90). The continuous mean particle size increase from birth to maturity shows the same rate but a different rhythm for the two synaptic sites. The results indicate that fractionation do not disturb the correlation between the particle size and age thus outlining the stability of the developing synaptic membrane morphology to physical treatments.

Freeze-etched neuronal growth cones from rat cerebral cortex at birth: plasma membrane morphology in relation to synapse formation

Isolated growth cones from the cerebral cortex of newborn rats were studied using the freeze-etching technique. The intramembranous structure of their plasma membranes was examined in detail and synaptic sites were found. Their membrane morphology was compared with that of the synaptic sites in adult animals and several differences between them were established. The importance of the present results for understanding the formation and development of the synaptic sites in the cerebral cortex is outlined.

Freeze-etched postsynaptic membranes in the visual cortex reveal different types of synapses including mixed synapses

The intramembranous structure of the postsynaptic membranes in the rat visual cortex was examined. Simple, complex and mixed synapses were differentiated according to the shape of the postsynaptic particle aggregations. The present data support the existence of all intermediate stages schematically presented in the hypothesis describing a synapse division. The advantage of the freeze-etching technique for the study of the shape of the active zones is emphasized.