The major trigger for CA3 discharge is the afferent input from the dentate gyrus granule cells, from which mossy fiber terminals create very complex synapses on the proximal part of the CA3 apical dendrite in the stratum lucidum. Here they contact very complex dendritic spines. Glutamate release from single terminals evokes a large non-NMDA mediated EPSP. The most proximal regions of CA3 pyramidal dendrites receive mossy fiber input exclusively, mid-dendritic regions (strata radiatum on the apical side and the oriens on the basal side) receive principally associational and Commissural fibers (from other CA3 cells), and the distal apical dendrites (stratum lacunosum-moleculare) receive input from the temproammonic afferents (from the entorhinal cortex). Mossy fiber input to CA3 exhibits different plasticity than that of typical long term potentiation because it is dependent on (or at least sensitive to) monoaminergic (see monoamine) activation of the cAMP 2nd messenger system.