Summary
Quantitation of synapses at different postnatal ages has been undertaken in the cerebral cortex of the rat. In this study axial ratios of presynaptic bags, proportion of cortex occupied by presynaptic bags and numbers of synapses per unit volume of cortex have been estimated. Observations on synaptic vesicle packing densities have also been made.
Synaptic bags become increasingly spherical up to 7 days of age and become more elongated thereafter. The proportion of cortex occupied by presynaptic bags increases rapidly up to 7 days of age and then at a decelerated rate up to maturity. The number of synapses per unit volume increases slowly over the first four days after which there is a rapid increase to 14 days, followed by a decelerated rate.
The average presynaptic bag shows marked changes in volume with increasing age which indicate the probability of two stages of synaptic development. This two stage development is further reflected in the estimates on vesicle packing densities. The implications of the results are discussed in relationship to changes in functional activity of the cortex during postnatal development.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Aghajanian, G. K., Bloom, F. E.: The formation of synaptic junctions in developing rat brain—a quantitative electron microscopic study. Brain Res. 6, 716–727 (1967).
Armstrong-James, M. A.: Histological and neurophysiological studies on the postnatal development of the rat cerebral cortex. Ph. D. Thesis, University of Bristol (1965).
Bondareff, W., Pysh, J. J.: Distribution of the extracellular space during postnatal maturation of rat cerebral cortex. Anat. Rec. 160, 773–780 (1968).
Brizzee, K. R., Jacobs, L. A.: Early postnatal changes in neuron packing density and volumetric relationships in the cerebral cortex of the white rat. Growth 23, 337–347 (1959).
—, Vogt, J., Karetchko, X.: Postnatal changes in glia-neuron index with comparison of methods of cell enumeration in the white rat. Progr. Brain Res. 4, 136–146 (1964).
Cragg, B. G.: The density of synapses and neurones in the motor and visual areas of the cerebral cortex. J. Anat. (Lond.) 101, 639–654 (1967a).
—: Changes in visual cortex on first exposure of rats to light. Nature (Lond.) 215, 251 (1967b).
Curtis, D. R., Eccles, J. C.: Synaptic action during and after repetitive stimulation. J. Physiol. (Lond.) 150, 374–398 (1960).
Delesse, M. A.: Procédé mécanique pour déterminer la composition des roches. C. R. Acad. Sci. 25, 544 (1847).
Eayrs, J. T., Goodhead, B.: Postnatal development of the cerebral cortex in the rat. J. Anat. (Lond.) 93, 385–402 (1959).
Johnson, F. R., Armstrong-James, M. A.: Morphology of superficial postnatal cerebral cortex with special reference to synapses. Z. Zellforsch. 110, 540–558 (1970).
Purpura, D. P., Shofer, R. J., Scarff, T.: Properties of synaptic activities and spike potentials of neurons in immature neocortex. J. Neurophysiol. 28, 925–942 (1965).
Sugita, N.: Comparative studies on the growth of the cerebral cortex. 5. I. On the area of the cortex and the brain cells in a unit volume, measured on the frontal and sagittal sections of the albino rat brain, together with the changes in these characters according to the brain. 5. II. On the area of the cortex and the brain cells in a unit volume, measured on the frontal and sagittal sections of the brain in the Norway rat (Mus rattus norvegiens) compared with the corresponding data for the albino rat. J. comp. Neurol. 29, 61–278 (1918).
Weibel, E. R., Gomez, P. M.: A principle for counting tissue structures on random sectioning. J. appl. Physiol. 17, 343–348 (1962).
—, Kistler, G. S., Scherle, W. F.: Practical stereological methods for morphometric cytology. J. Cell Biol. 30, 23–38 (1966).
Author information
Authors and Affiliations
Additional information
The authors wish to express their thanks to Mr. R. Birchenough and Mr. J. Manston for much technical assistance.
Rights and permissions
About this article
Cite this article
Armstrong-James, M., Johnson, R. Quantitative studies of postnatal changes in synapses in rat superficial motor cerebral cortex. Z. Zellforsch. 110, 559–568 (1970). https://doi.org/10.1007/BF00330104
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00330104