Modulation of synaptic transmission and long-term potentiation: effects on paired pulse facilitation and EPSC variance in the CA1 region of the hippocampus
T. Manabe, D. J. Wyllie, D. J. Perkel and R. A. Nicoll Department of Pharmacology, University of California, San Francisco 94143-0450. 1. Whole-cell patch-clamp recordings of excitatory postsynaptic currents (EPSCs) were made from guinea pig hippocampal CA1 pyramidal cells. The sensitivity of paired...
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Veröffentlicht in: | Journal of neurophysiology 1993-10, Vol.70 (4), p.1451-1459 |
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Zusammenfassung: | T. Manabe, D. J. Wyllie, D. J. Perkel and R. A. Nicoll
Department of Pharmacology, University of California, San Francisco 94143-0450.
1. Whole-cell patch-clamp recordings of excitatory postsynaptic currents
(EPSCs) were made from guinea pig hippocampal CA1 pyramidal cells. The
sensitivity of paired pulse facilitation (PPF) and EPSC variance to changes
in synaptic transmission was investigated and the results were compared
with the changes in these parameters evoked by long-term potentiation
(LTP). 2. Presynaptic manipulations, such as activation of presynaptic
gamma-aminobutyric acid-B receptors by baclofen, blockade of presynaptic
adenosine receptors by theophylline, blockade of presynaptic potassium
channels by cesium, and increasing the Ca(2+)-Mg2+ ratio in the external
recording solution, each reliably changed PPF in a fashion reciprocal to
the change in the EPSC amplitude. However, recruitment of additional
synaptic release sites by increasing stimulus strength and antagonism of
non-N-methyl-D-aspartate (NMDA) glutamate receptors by
6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) failed to alter PPF. 3.
Presynaptic manipulations including increased stimulus strength gave the
predicted changes in the value of mean 2/variance (M2/sigma 2). Moreover,
postsynaptic manipulations that altered EPSC amplitude, including blockade
of non-NMDA receptors by CNQX, or changing the holding potential of the
postsynaptic cell, gave little change in M2/sigma 2, as would be predicted
for manipulations resulting in a uniform postsynaptic change. 4. LTP caused
no change in PPF, whereas the presynaptic manipulations, which caused a
similar amount of potentiation to that induced by LTP, significantly
decreased PPF. On the other hand, LTP did increase M2/sigma 2, although the
increase was less than that predicted for a purely presynaptic
mechanism. |
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ISSN: | 0022-3077 1522-1598 |
DOI: | 10.1152/jn.1993.70.4.1451 |