Journal of Neuroscience, Vol 14, 6707-6714, Copyright © 1994 by Society for Neuroscience
Effect of adenosine-induced changes in presynaptic release probability on long-term potentiation in the hippocampal CA1 region
F Asztely, MY Xiao, H Wigstrom and B Gustafsson
Department of Physiology, University of Goteborg, Sweden.
In the present study some characteristics of long-term potentiation (LTP)
in the hippocampal CA1 region were examined under different conditions of
transmitter release. Adenosine A1 agonist/antagonists, or in some instances
changes in the extracellular calcium/magnesium ratio, were used to alter
release probability. The overall LTP time course (onset latency, growth
phase, and subsequent decay for both the non- NMDA and NMDA
receptor-mediated EPSPs) following a brief tetanus was essentially the same
over an almost 10-fold variation in release probability (measured as change
in field EPSP magnitude). The major difference observed was a faster
initial decay of LTP evoked at low levels of release probability, possibly
related to impaired induction conditions. It was also observed that LTP
induced at one level of release probability occluded that induced at a
lower (or higher) level, and that changes in release probability induced by
adenosine agonist/antagonists affected potentiated and "naive" EPSPs to an
equal extent. Taken together, these data do not provide support for the
notion of different locations for LTP expression at different conditions of
release probability. The results are also more compatible with the notion
of a single, rather than several, expression mechanism(s) within the first
hour of LTP in the hippocampal CA1 region.