J Physiol 585.3 (2007) pp. 853-865, doi:10.1113/jphysiol.2007.143925

Differential modulation of short-term synaptic dynamics by long-term potentiation at mouse hippocampal mossy fibre synapses.

A. Gundlfinger, C. Leibold, K. Gebert, M. Moisel, D. Schmitz, and R. Kempter.

Synapses continuously experience short- and long-lasting activity-dependent changes in synaptic strength. Long-term plasticity hereby describes persistent alterations in synaptic efficacy, whereas short-term plasticity (STP) reflects the instantaneous and reversible modulation of synaptic strength in response to varying presynaptic stimuli. The hippocampal mossy fibre synapse onto CA3 pyramidal cells is known to exhibit both a presynaptic, NMDA-receptor independent form of long-term potentiation (LTP) and a pronounced form of STP. A detailed description of their exact interdependence is however lacking. Here, using electrophysiological and computational techniques, we have developed a descriptive model of transmission dynamics to quantify plasticity at the mossy fibre synapse. STP at this synapse is best described by two facilitatory processes acting on timescales of a few hundred milliseconds and about ten seconds. We find that these distinct types of facilitation are differentially influenced by LTP such that the impact of the fast process is weakened as compared to that of the slow process. This attenuation is reflected by a selective decrease of not only the amplitude but also the time constant of the fast facilitation. We henceforth argue that multidimensional LTP, involving a modulation of parameters determining both amplitude and timecourse of STP, serves as a mechanism to adapt the mossy fibre to its synaptic input.

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