Summary
The morphology of perforated synapses in the molecular layer of rat parietal cortex has been studied in 28-day-old animals. Of the perforated synapses analyzed, 92% were axospinous and of these all had asymmetrical contacts. A spinule was present in 20% of them, and 63% had a negative curvature (concave with respect to the presynaptic terminal) overall. Up to 95% of perforated synapses had one or more negatively-curved segments. The perforated synapses studied were characterized by postsynaptic densities (PSD) with a mean length of 581 nm, compared with 233 nm for non-perforated synapses.
A study of over 100 serially sectioned synapses demonstrated that, in perforated synapses, the PSD and perforations often had a highly irregular shape and arrangement, the site of the perforation frequently projected into the presynaptic terminal, and coated evaginations of membrane, or coated vesicles, were sometimes found at the site of a perforation or towards the periphery of perforated PSDs. Preliminary reconstructions of perforated synapses suggest that, for descriptive purposes, three types can be recognized. Criteria are formulated for determining, on the basis of a study of single sections, which non-perforated profiles belong to perforated synapses.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Adams I, Jones DG (1982) Synaptic remodelling and astrocytic hypertrophy in rat cerebral cortex from early to late adulthood. Neurobiol Aging 3:179–186
Adinolfi AM (1972) Morphogenesis of synaptic junctions in layers I and II of the somatic sensory cortex. Exp Neurol 34:372–382
Calverley RKS, Bedi KS, Jones DG (1987) Estimation of the numerical density of synapses in rat neocortex. A comparison of the ‘disector’ with an ‘unfolding’ method. J Comp Neurol (in press)
Calverley RKS, Jones DG (1987) Determination of the numerical density of perforated synapses in rat neocortex. Cell Tissue Res (in press)
Carlin RK, Siekevitz P (1983) Plasticity in the central nervous system: do synapses divide? Proc Natl Acad Sci USA 80:3517–3521
Cohen RS, Siekevitz P (1978) Form of the postsynaptic density: a serial section study. J Cell Biol 78:36–46
de Groot DMG, Bierman EPS (1983) The complex-shaped ‘perfoated’ synapses, a problem in quantitative stereology of the brain. J Microsc 131:355–360
Devon RM, Jones DG (1981) Synaptic parameters in developing rat cerebral cortex: comparison of anaesthetized and unanaesthetized states. Dev Neurosci 4:351–362
Dyson SE, Jones DG (1980) Quantitation of terminal parameters and their interrelationships in maturing central synapses: a perspective for experimental studies. Brain Res 183:43–59
Dyson SE, Jones DG (1984) Junction differentiation and splitting as a mechanism for modifying connectivity. Dev Brain Res 13:125–137
Jones DG, Colangelo W (1985) Ultrastructural investigation into the influence of ethanol on synaptic maturation in rat neocortex. I. Qualitative assessment. Dev Neurosci 7:94–106
Jones DG, Cullen AM (1979) A quantitative investigation of some presynaptic terminal parameters during synaptogenesis. Exp Neurol 64:245–259
Jones DG, Devon RM (1978) An ultrastructural study into the effects of pentobarbitone on synaptic organization. Brain Res 147:47–63
Nieto-Sampedro M, Hoff SF, Cotman CW (1982) Perforated postsynaptic densities: probable intermediates in synapse turnover. Proc Natl Acad Sci USA 79:5718–5722
Peters A, Kaiserman-Abramof IR (1969) The small pyramidal neuron of the rat cerebral cortex. Z Zellforsch 100:487–506
Siekevitz P (1985) The postsynaptic density: a possible role in longlasting effects in the central nervous system. Proc Natl Acad Sci USA 82:3494–3498
Spacck J (1985a) Three-dimensional analysis of dendritic spines. II. Spine apparatus and other cytoplasmic components. Anat Embryol 171:235–243
Spacek J (1985b) Relationships between synaptic junctions, puncta adhaerentia and the spine apparatus at neocortical axo-spinous synapses. A serial section study. Anat Embryol 173:129–135
Spacek J, Hartmann M (1983) Three-dimensional analysis of dendritic spines. I. Quantitative observations related to dendritic spine and synaptic morphology in cerebral and cerebellar cortices. Anat Embryol 167:289–310
Tarrant SB, Routtenberg A (1977) The synaptic spinule in the dendritic spine: electron microscopic study of the hippocampal dentate gyrus. Tiss Cell 9:461–473
Tarrant SB, Routtenberg A (1979) Postsynaptic membrane and spine apparatus: proximity in dendritic spines. Neurosci Lett 11:289–294
Van der Want JJL, Cornelisse JTWA, Vrensen GFJM (1985) The size and curvature of synapses in the cerebellar cortex of the cat. Anat Embryol 171:83–89
Vrensen G, Nunes-Cardozo J, Muller L, Van der Want J (1980) The presynaptic grid: a new approach. Brain Res 184:23–40
Wilson CJ, Groves PM, Kitai ST, Linder JC (1983) Three-dimensional structure of dendritic spines in the rat neostriatum. J Neurosci 3:383–398
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Calverley, R.K.S., Jones, D.G. A serial-section study of perforated synapses in rat neocortex. Cell Tissue Res. 247, 565–572 (1987). https://doi.org/10.1007/BF00215750
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00215750