Evidence for Common Expression Mechanisms Underlying Heterosynaptic
and Associative Long-Term Depression in the Dentate Gyrus.
Christie, Brian R., David Stellwagen, and Wickliffe C. Abraham.
Department of Psychology and the Neuroscience Research Centre, University
of Otago, Dunedin, New Zealand.
APStracts 2:0144N, 1995.
Summary and Conclusions
1. The extent to which heterosynaptic and prime-associative stimulation
protocols generate different forms of long-term depression (LTD) was assessed
in the lateral perforant path synapses terminating on dentate gyrus granule
cells in pentobarbital anesthetized rats. 2. Heterosynaptic LTD was induced in
the lateral path by repeated tetanization of the medial path. Prime-
associative LTD of the lateral path was induced by alternating high-frequency
conditioning trains to the medial path and single shocks to the lateral path
at 100 ms intervals, all occurring 10 min following priming stimulation of the
lateral path (5 Hz, 80 pulses). 3. Induction of LTD by one administration of
the prime-associative protocol was normally greater in magnitude that the LTD
induced by the heterosynaptic protocol. Saturation of LTD by repeated delivery
of the prime-associative protocol completely occluded the subsequent induction
of LTD by the heterosynaptic protocol. Saturation of LTD by repeated delivery
of the heterosynaptic protocol produced an 80% occlusion of the LTD generated
by the prime-associative protocol. 4. These data support the hypothesis that
activity-dependent (associative) and activity-independent (heterosynaptic) LTD
involve common expression mechanisms, despite having demonstrably different
induction mechanisms.
Received 8 November 1994; accepted in final form 5 May 1995.
APS Manuscript Number J706-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 16 May 1995.