Presynaptic kainate receptor mediation of frequency facilitation at hippocampal mossy fiber synapses

Inhibition of transmitter release by presynaptic receptors is widespread in the central nervous system and is typically mediated via metabotropic rece ptors; In contrast, very little is known about facilitatory receptors, and synaptic activation of a facilitatory autoreceptor has not been established . Here we show that activation of presynaptic kainate receptors can facilit ate transmitter release from hippocampal mossy fiber synapses. Synaptic act ivation of these presumed ionotropic kainate receptors is very fast (<10 ms ) and Lasts for seconds. Thus, these presynaptic kainate receptors contribu te to the shortterm plasticity characteristics of mossy fiber synapses, whi ch were previously thought to be an intrinsic property of the synapse.