Quantal analysis and synaptic efficacy in the CNS

Korn, Henri; Faber, Donald S.

doi:10.1016/0166-2236(91)90042-s

Cited by 266 publications

(152 citation statements)

References 46 publications

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“…Because a single hippocampal bouton normally releases at most a single quantum of neurotransmitter Wang, 1994, 1995), Katz's (1969) N s , the number of release sites, would correspond to the number of active zones (and to the number of boutons). This conclusion is in agreement with earlier proposals (see Zucker, 1989;Redman, 1990;Korn and Faber, 1991;and Walmsley, 1991). Although an old idea dating from Zucker (1973), the release site and active zone identification has not been widely accepted.…”

Section: Active Zone and Release Site Correspondencesupporting

confidence: 83%

Quantitative Ultrastructural Analysis of Hippocampal Excitatory Synapses

1997

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From three-dimensional reconstructions of CA1 excitatory synapses in the rodent hippocampus and in culture, we have estimated statistical distributions of active zone and postsynaptic density (PSD) sizes (average area ϳ0.04 m 2 ), the number of active zones per bouton (usually one), the number of docked vesicles per active zone (ϳ10), and the total number of vesicles per bouton (ϳ200), and we have determined relationships between these quantities, all of which vary from synapse to synapse but are highly correlated. These measurements have been related to synaptic physiology. In particular, we propose that the distribution of active zone areas can account for the distribution of synaptic release probabilities and that each active zone constitutes a release site as identified in the standard quantal theory attributable to Katz (1969).Key words: synaptic vesicle; active zone; release; statistical distribution; hippocampus; release probabilitySince the pioneering work of Katz and his collaborators on synaptic f unction (summarized in Katz, 1969) and that of the early electron microscopists on synaptic structure (Palay and Palade, 1955;L use, 1956;Wyckoff and Young, 1956), a consistent goal of neurobiologists has been to identif y the structural basis for the entities identified in Katz's theory of synaptic transmission (Katz, 1969). The synaptic vesicle is generally accepted as corresponding to Katz's quantum, although still without definitive evidence. The number of release sites [N s in Katz's (1969) scheme] associated with an axon has been identified with the total number of releasable vesicles, with the number of boutons, and with the number of active zones (Zucker, 1973;Jack et al., 1981;Korn et al., 1981;Neale et al., 1983;Redman and Walmsley, 1983;Walmsley et al., 1985;Pun et al., 1986;Propst and Ko, 1987;Redman, 1990;Walmsley, 1991;Pierce and Mendell, 1993;Pierce and Lewin, 1994). A possible anatomical counterpart of Katz's release probability p has been subject to less speculation, but several authors have noted that p might be related to synaptic size (see Pierce and Lewin, 1994).With the development of optical techniques to study synaptic transmission and the extension of these techniques to hippocampal neurons in culture (Ryan et al., 1993;Ryan and Smith, 1995;Ryan et al., 1996), many synaptic properties can now be investigated in culture at the level of single central synapses. Although individual hippocampal synapses differ greatly from one another with respect to any one of these properties, a variety of the properties are highly correlated with the release probability of the synapse (Ryan et al., 1996;Murthy et al., 1997). To relate results from physiological investigations of synapse populations to synaptic structure, one must know the statistical distribution of morphological characteristics. Current statistical information about hippocampal synapses comes from studies by Harris and Stevens (1989), Harris et al. (1992), Sorra and Harris (1993), and Harris and Sultan (1995), but this work has focus...

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Section: Active Zone and Release Site Correspondencesupporting

confidence: 83%

Quantitative Ultrastructural Analysis of Hippocampal Excitatory Synapses

1997

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“…Thus, for example, if quanta1 release saturates available receptors at central synapses (Redman, 1990;Korn and Faber, 1991;Tong and Jahr, 1994), spine growth incorporating more postsynaptic receptors could yield increased q. Indeed, larger spines generally have larger postsynaptic densities and, presumably, more receptors and ion channels (Harris and Stevens, 1989;Lisman and Harris, 1993); increased size of the postsynaptic density has been reported by Desmond and Levy (1986b), as remarked earlier, in the subpopulation of large spines whose frequency is increased by LTP at the apparent expense of smaller spines.…”

Section: Discussionmentioning

confidence: 63%

Repeated confocal imaging of individual dendritic spines in the living hippocampal slice: evidence for changes in length and orientation associated with chemically induced LTP

et al. 1995

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Using confocal microscopy in conjunction with microdrop application of Dil, we have imaged and measured individual dendritic spines of living hippocampal CA1 pyramidal neurons in acute brain slices, before and approximately 3 hr after induction of long-term potentiation by chemical means. Statistical analysis of changes in the length of individual spines, and comparison with results of Monte Carlo simulations, suggests that two forms of structural change occur in chemically induced long-term potentiation: growth of a subpopulation of small spines, and angular displacement of spines. These changes could provide a structural basis for the expression of long-term potentiation.

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“…5-HT (600 nM) partially inhibited the EPSC (Fig. 2 A-C M 2 ͞ 2 analysis is invalid if release probability is high, if the EPSCs arise from a pool of synapses with varying properties, or if the stimulus paradigm allows failure of the presynaptic action potential to invade the terminal (34). None of these conditions apply in our study.…”

Section: -Ht Reduces Evoked Unitary Quantalmentioning

confidence: 56%

“…It is less clear in the CNS, where CV is likely to be high (ref. 34; CV at the lamprey synapse is high, 0.5 Ϯ 0.1; n ϭ 4). Nevertheless, this measure predicts a presynaptic locus with changes in presynaptic Ca 2ϩ entry, and a postsynaptic locus after postsynaptic receptor blockade.…”

Section: Methodsmentioning

confidence: 99%