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Different forms of LTD in the CA1 region of the hippocampus: role of age and stimulus protocol
Author(s) -
Kemp Nicola,
McQueen Jane,
Faulkes Suzanna,
Bashir Zafar I.
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00903.x
Subject(s) - nmda receptor , hippocampal formation , neuroscience , stimulus (psychology) , hippocampus , long term depression , stimulation , receptor , psychology , medicine , ampa receptor , psychotherapist
In this study, we have investigated the developmental range over which different stimulus protocols induce long‐term depression (LTD). Low‐frequency stimulation (LFS; 900 stimuli, 1 Hz) produced LTD in hippocampal slices from rats younger than ∼ 40 days old, but not in animals aged between ∼ 40 days and 16 weeks. We demonstrate, however, that different stimulus protocols can result in LTD in the adult hippocampus. Whilst one paired‐pulse low‐frequency stimulus protocol [PP‐LFS; 50 ms paired‐pulse interval (PPI), 900 pairs of stimuli] produced N‐methyl‐ d ‐aspartate (NMDA) receptor‐independent LTD, another PP‐LFS protocol (200 ms PPI; 900 pairs) produced NMDA receptor‐dependent LTD. Furthermore, the saturation of NMDA receptor‐dependent LTD did not prevent the induction of further NMDA receptor‐independent LTD. This lack of occlusion suggests that different mechanisms of expression may underlie each of the above forms of LTD in the adult hippocampus. In contrast to the adult hippocampus, NMDA receptor‐dependent LTD was induced by both LFS and PP‐LFS (50 ms PPI) in slices from young animals (12–20 days). Although they share a common induction mechanism, LTD induced by PP‐LFS may be expressed through other mechanisms in addition to those underlying LFS‐induced LTD in the young hippocampus. In conclusion, the results in this study demonstrate that mechanisms of long‐term synaptic depression within the hippocampus can alter radically with development of the central nervous system and with the use of different induction protocols.