Amplitude fluctuations in small EPSPs recorded from CA1 pyramidal cells in the guinea pig hippocampal slice

EPSPs have been evoked in CA1 pyramidal cells by (1) activation of single CA3 neurons (unitary EPSPs), and (2) low-intensity stimuli to the CA1 stratum radiatum. Five unitary EPSPs were obtained; their mean peak amplitudes ranged from 85 to 275 microV and 3 of the 5 showed fluctuations in amplitude that were too great to be attributed to baseline noise. After subtraction of the variance due to the noise, these EPSPs had coefficients of variation much higher than those reported for variability in the quantal EPSP in other preparations. These results suggest that intermittent transmitter release is a major cause of EPSP amplitude fluctuation at this synapse. A noise deconvolution technique based on a nonrestrictive model of transmitter release was applied to the EPSPs obtained in this study. For 2 of the EPSPs evoked by stratum radiatum stimulation, the amplitudes fluctuated between discrete values that were sufficiently separated with respect to the noise to be resolved by the deconvolution procedure. Quantal increments of 224 and 193 microV were determined for the 2 EPSPs.

[1]  T. Blackstad,et al.  An electron microscopic study of the stratum radiatum of the rat hippocampus (regio superior, CA 1) with particular emphasis on synaptology , 1962, The Journal of comparative neurology.

[2]  V. Hasselblad.  Estimation of parameters for a mixture of normal distributions , 1966 .

[3]  A. R. Martin,et al.  Quantal Nature of Synaptic Transmission , 1966 .

[4]  P. Andersen.  Organization of Hippocampal Neurons and Their Interconnections , 1975 .

[5]  D. Rubin,et al.  Maximum likelihood from incomplete data via the EM - algorithm plus discussions on the paper , 1977 .

[6]  E. McLachlan.  The statistics of transmitter release at chemical synapses. , 1978, International review of physiology.

[7]  P. Andersen,et al.  A comparison of distal and proximal dendritic synapses on CA1 pyramids in guinea‐pig hippocampal slices in vitro , 1980, The Journal of physiology.

[8]  G Lynch,et al.  Brief bursts of high-frequency stimulation produce two types of structural change in rat hippocampus. , 1980, Journal of neurophysiology.

[9]  Stephen Redman,et al.  The recovery of a random variable from a noisy record with application to the study of fluctuations in synaptic potentials , 1980, Journal of Neuroscience Methods.

[10]  J. Jack,et al.  The components of synaptic potentials evoked in cat spinal motoneurones by impulses in single group Ia afferents. , 1981, The Journal of physiology.

[11]  H Korn,et al.  Transmission at a central inhibitory synapse. II. Quantal description of release, with a physical correlate for binomial n. , 1982, Journal of neurophysiology.

[12]  P Andersen,et al.  Summation of excitatory postsynaptic potentials in hippocampal pyramidal cells. , 1983, Journal of neurophysiology.

[13]  L. Ling,et al.  Recovering the parameters of finite mixtures of normal distributions from a noisy record: an empirical comparison of different estimating procedures , 1983, Journal of Neuroscience Methods.

[14]  B. Walmsley,et al.  Amplitude fluctuations in synaptic potentials evoked in cat spinal motoneurones at identified group Ia synapses. , 1983, The Journal of physiology.

[15]  T. Babb,et al.  Demonstration of axonal projections of neurons in the rat hippocampus and subiculum by intracellular injection of HRP , 1983, Brain Research.

[16]  N. Tamamaki,et al.  A whole image of the hippocampal pyramidal neuron revealed by intracellular pressure-injection of horseradish peroxidase , 1984, Brain Research.

[17]  J. Clements,et al.  Presynaptic inhibition of synaptic potentials evoked in cat spinal motoneurones by impulses in single group Ia axons. , 1987, The Journal of physiology.

[18]  Grzegorz Hess,et al.  Quantal analysis of paired-pulse facilitation in guinea pig hippocampal slices , 1987, Neuroscience Letters.

[19]  B. Walmsley,et al.  The probabilistic nature of synaptic transmission at a mammalian excitatory central synapse , 1987, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[20]  P Anderson,et al.  Thresholds of action potentials evoked by synapses on the dendrites of pyramidal cells in the rat hippocampus in vitro. , 1987, The Journal of physiology.

[21]  D A Turner,et al.  Waveform and amplitude characteristics of evoked responses to dendritic stimulation of CA1 guinea‐pig pyramidal cells. , 1988, The Journal of physiology.