New ways of looking at synapses

  • Michael Frotscher
  • Shanting Zhao
  • Werner Graber
  • Alexander Drakew
  • Daniel Studer
Original Paper

Abstract

Current concepts of synaptic fine-structure are derived from electron microscopic studies of tissue fixed by chemical fixation using aldehydes. However, chemical fixation with glutaraldehyde and paraformaldehyde and subsequent dehydration in ethanol result in uncontrolled tissue shrinkage. While electron microscopy allows for the unequivocal identification of synaptic contacts, it cannot be used for real-time analysis of structural changes at synapses. For the latter purpose advanced fluorescence microscopy techniques are to be applied which, however, do not allow for the identification of synaptic contacts. Here, two approaches are described that may overcome, at least in part, some of these drawbacks in the study of synapses. By focusing on a characteristic, easily identifiable synapse, the mossy fiber synapse in the hippocampus, we first describe high-pressure freezing of fresh tissue as a method that may be applied to study subtle changes in synaptic ultrastructure associated with functional synaptic plasticity. Next, we propose to label presynaptic mossy fiber terminals and postsynaptic complex spines on CA3 pyramidal neurons by different fluorescent dyes to allow for the real-time monitoring of these synapses in living tissue over extended periods of time. We expect these approaches to lead to new insights into the structure and function of central synapses.

Keywords

Synapse structure High-pressure freezing Real-time microscopy Mossy fiber Dendritic spines 

References

  1. Acsády L, Kamondi A, Sik A, Freund T, Buzsáki G (1998) GABAergic cells are the major postsynaptic targets of mossy fibers in the rat hippocampus. J Neurosci 18:3386–3403PubMedGoogle Scholar
  2. Andersen P, Bliss TVP, Skrede KK (1971) Lamellar organization of hippocampal excitatory pathways. Exp Brain Res 13:222–238Google Scholar
  3. Bischofberger J, Engel D, Frotscher M, Jonas P (2006) Timing and efficacy of transmitter release at mossy fiber synapses in the hippocampal network. Pflügers Arch Eur J Physiol 453:361–372CrossRefGoogle Scholar
  4. Blackstad TW, Kjaerheim A (1961) Special axodendritic synapses in the hippocampal cortex: electron and light microscopic studies on the layer of mossy fibers. J Comp Neurol 117:113–159CrossRefGoogle Scholar
  5. Chicurel ME, Harris KM (1992) Three-dimensional analysis of the structure and composition of CA3 branched dendritic spines and their synaptic relationships with mossy fiber boutons in the rat hippocampus. J Comp Neurol 325:169–182PubMedCrossRefGoogle Scholar
  6. Engert E, Bonhoeffer T (1999) Dendritic spine changes associated with hippocampal long-term synaptic plasticity. Nature 339:66–70Google Scholar
  7. Förster E, Zhao S, Frotscher M (2006) Laminating the hippocampus. Nat Rev Neurosci 7:259–267PubMedCrossRefGoogle Scholar
  8. Frotscher M (1985) Mossy fibres form synapses with identified pyramidal basket cells in the CA3 region of the guinea pig hippocampus: a combined Golgi-electron microscope study. J Neurocytol 14:245–259PubMedCrossRefGoogle Scholar
  9. Frotscher M (1989) Mossy fiber synapses on glutamate decarboxylase-immunoreactive neurons: evidence for feed-forward inhibition in the CA3 region of the hippocampus. Exp Brain Res 75:441–445PubMedGoogle Scholar
  10. Frotscher M, Deller T (2005) Role of the spine apparatus in synaptic plasticity. In: Stanton PK, Bramham C, Scharfman HE (eds) Synaptic plasticity and transsynaptic signaling, Springer, Berlin pp 519–528CrossRefGoogle Scholar
  11. Frotscher M, Gähwiler BH (1988) Synaptic organization of intracellularly stained CA3 pyramidal neurons in slice cultures of rat hippocampus. Neuroscience 24:541–551PubMedCrossRefGoogle Scholar
  12. Frotscher M, Misgeld U, Nitsch C (1981) Ultrastructure of mossy fiber endings in in vitro hippocampal slices. Exp Brain Res 41:247–255PubMedGoogle Scholar
  13. Frotscher M, Soriano E, Misgeld U (1994) Divergence of hippocampal mossy fibers. Synapse 16:148–160PubMedCrossRefGoogle Scholar
  14. Frotscher M, Zafirov S, Heimrich B (1995) Development of identified neuronal types and of specific synaptic connections in slice cultures of rat hippocampus. Prog Neurobiol 45:143–164PubMedCrossRefGoogle Scholar
  15. Frotscher M, Jonas P, Sloviter RS (2006) Synapses formed by normal and abnormal hippocampal mossy fibers. Cell Tissue Res 326:361–367PubMedCrossRefGoogle Scholar
  16. Gähwiler MH, Capogna M, Debanne D, McKinney RA, Thompson SM (1997) Organotypic slice cultures: a technique has come of age. TINS 20:471–477PubMedGoogle Scholar
  17. Gray EG (1959) Axo-somatic and axo-dendritic synapses of the cerebral cortex: an electron microscopic study. J Anat 83:420–433Google Scholar
  18. Hallermann S, Pawlu C, Jonas P, Heckmann M (2003) A large pool of releasable vesicles in a cortical glutamatergic synapse. Proc Natl Acad Sci USA 100:8975–8980PubMedCrossRefGoogle Scholar
  19. Hamlyn LH (1962) The fine structure of the mossy fibre endings in the hippocampus of the rabbit. J Anat 97:112–120Google Scholar
  20. Matus A (2000) Actin-based plasticity in dendritic spines. Science 290:754–758PubMedCrossRefGoogle Scholar
  21. Matus A, Frotscher M (2005) Synapse. In: Nadel L (ed) Encyclopedia of cognitive science, vol 4. Wiley, Chichester, pp 301–307Google Scholar
  22. Nadarajah B, Parnavelas JG (2002) Modes of neuronal migration in the developing cerebral cortex. Nat Rev Neurosci 3:423–432PubMedCrossRefGoogle Scholar
  23. Peters A, Palay SL, Webster HD (1991) The fine structure of the nervous system. Neurons and their supporting cells. Oxford University Press, OxfordGoogle Scholar
  24. Rizzoli SO, Betz WJ (2005) Synaptic vesicle pools. Nat Rev Neurosci 6:57–69PubMedCrossRefGoogle Scholar
  25. Rostaing P, Real E, Siksou L, Lechaire J-P, Boudier T, Boeckers TM, Gertler F, Gundelfinger ED, Triller A, Marty S (2006) Analysis of synaptic ultrastructure without fixative using high-pressure freezing and tomography. Eur J Neurosci 24:3463–3473PubMedCrossRefGoogle Scholar
  26. Schikorski T, Stevens CF (2001) Morphological correlates of functionally defined synaptic vesicle populations. Nat Neurosci 4:391–395PubMedCrossRefGoogle Scholar
  27. Spacek J (1985) Three-dimensional analysis of dendritic spines. II. Spine apparatus and other cytoplasmic components. Anat Embryol 171:235–243PubMedCrossRefGoogle Scholar
  28. Spacek J, Harris KM (1997) Three-dimensional organization of smooth endoplasmic reticulum in hippocampal CA1 dendrites and dendritic spines of the immature and mature rat. J Neurosci 17:190–203PubMedGoogle Scholar
  29. Squire LR, Stark CE, Clark RE (2004) The medial temporal lobe. Annu Rev Neurosci 27:279–306PubMedCrossRefGoogle Scholar
  30. Steward O, Levy WB (1982) Preferential localization of polyribosomes under the base of dendritic spines in granule cells of the dentate gyrus. J Neurosci 2:284–291PubMedGoogle Scholar
  31. Studer D, Michel M, Müller M (1989) High pressure freezing comes of age. Scanning Microsc Suppl 3:253–269PubMedGoogle Scholar
  32. Studer D, Michel M, Wohlwend M, Hunziker EB, Buschmann MD (1995) Vitrification of articular cartilage by high-pressure freezing. J Microsc 179:321–332PubMedGoogle Scholar
  33. Studer D, Graber W, Al-Amoudi A, Eggli P (2001) A new approach for cryofixation by high-pressure freezing. J Microsc 203:285–294PubMedCrossRefGoogle Scholar
  34. Toni N, Buchs P-A, Nikonenko I, Bron CR, Muller D (1999) LTP induces synaptogenesis by duplication of synaptic spines contacting a single axon terminal. Nature 402:421–425PubMedCrossRefGoogle Scholar
  35. Willig KI, Rizzoli SO, Westphal V, Jahn R, Hell SW (2006) STED microscopy reveals that synaptotagmin remains clustered after synaptic vesicle exocytosis. Nature 440:935–939PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Michael Frotscher
    • 1
  • Shanting Zhao
    • 1
  • Werner Graber
    • 2
  • Alexander Drakew
    • 1
  • Daniel Studer
    • 2
  1. 1.Institute of Anatomy and Cell BiologyUniversity of FreiburgFreiburgGermany
  2. 2.Institute of AnatomyUniversity of BernBern 9Switzerland

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