Studies of long-term depression of synaptic activity in the rat hippocampus
Studies of long-term depression of synaptic activity in the rat hippocampus
This thesis is concerned with the phenomenon of LTD in the CA1 region of the adult rat hippocampus studied using electrophysiological techniques.
Low-frequency stimulation (1Hz) for 500 pulses produced long-term depression (60mins post-LFS) from control values of the field epsp slope of 18 ± 3% (n=5) and population spike amplitude of 37 ± 11% (n=5). When 900 pulses were used the LTD of the field slope was deeper 60mins post-LFS measuring 38 ± 12% (n=5) whilst LTD of population spike amplitude was also deeper measuring 42 ± 13% (n=5) of control values. This LTD was input specific and possessed no heterosynaptic associative interactions during LFS and proved to be heavily dependent on the activation of NMDA-Rs. There appeared to be some form of GABAergic control as bicuculline blocked the maintenance of this depression. When postsynaptic Ca2+ was chelated by using the acetomethoxy form of BAPTA, the maintenance of LTD was blocked. Ca2+ entry, through L-type or T-type voltage-gated Ca2+ channels did not appear necessary as the selective antagonists nifedipine and Ni2+ did not block the LTD of either response.
There may have been a very weak metabotropic receptor component present which was overwhelmed by the dominant NMDA-R component, but activation of these receptors with L-CSA showed that this form of LTD did not appear to be mediated through a receptor linked to phospholipase D activation. Both presynaptic autoreceptors appeared to play a role in the modulation of the LTD after LFS was delivered as selective antagonists at both receptors blocked the maintenance 60mins post-LFS and the addition of 4AP, a known convulsant, also blocked the maintenance of this depression. During LFS both synaptic depression and reduced paired-pulse inhibition were observed.
University of Southampton
1997
Tisi, Stephen Vincent
(1997)
Studies of long-term depression of synaptic activity in the rat hippocampus.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis is concerned with the phenomenon of LTD in the CA1 region of the adult rat hippocampus studied using electrophysiological techniques.
Low-frequency stimulation (1Hz) for 500 pulses produced long-term depression (60mins post-LFS) from control values of the field epsp slope of 18 ± 3% (n=5) and population spike amplitude of 37 ± 11% (n=5). When 900 pulses were used the LTD of the field slope was deeper 60mins post-LFS measuring 38 ± 12% (n=5) whilst LTD of population spike amplitude was also deeper measuring 42 ± 13% (n=5) of control values. This LTD was input specific and possessed no heterosynaptic associative interactions during LFS and proved to be heavily dependent on the activation of NMDA-Rs. There appeared to be some form of GABAergic control as bicuculline blocked the maintenance of this depression. When postsynaptic Ca2+ was chelated by using the acetomethoxy form of BAPTA, the maintenance of LTD was blocked. Ca2+ entry, through L-type or T-type voltage-gated Ca2+ channels did not appear necessary as the selective antagonists nifedipine and Ni2+ did not block the LTD of either response.
There may have been a very weak metabotropic receptor component present which was overwhelmed by the dominant NMDA-R component, but activation of these receptors with L-CSA showed that this form of LTD did not appear to be mediated through a receptor linked to phospholipase D activation. Both presynaptic autoreceptors appeared to play a role in the modulation of the LTD after LFS was delivered as selective antagonists at both receptors blocked the maintenance 60mins post-LFS and the addition of 4AP, a known convulsant, also blocked the maintenance of this depression. During LFS both synaptic depression and reduced paired-pulse inhibition were observed.
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Published date: 1997
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Local EPrints ID: 462996
URI: http://eprints.soton.ac.uk/id/eprint/462996
PURE UUID: 733f6d11-cc71-4ddd-ad24-6ffb4716ca6c
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Date deposited: 04 Jul 2022 20:35
Last modified: 04 Jul 2022 20:35
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Author:
Stephen Vincent Tisi
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