Mossy fiber long-term potentiation shows specificity but no apparent cooperativity.

Specificity in long-term potentiation (LTP) means that synapses onto a postsynaptic cell can potentiate independently of one another. Cooperativity refers to a requirement that some threshold number of afferents be co-activated to evoke LTP with a high-frequency stimulus. The induction of long-term potentiation (LTP) at the associational/commissural synapses onto hippocampal CA3 pyramidal cells shows clear cooperativity. LTP of mossy fiber inputs to these cells does not. Mossy fiber LTP does show synapse specificity. These results bear on the cellular mechanisms and the functions of mossy fiber LTP.