MULTIDETERMINANT ROLE OF CALCIUM IN HIPPOCAMPAL SYNAPTIC PLASTICITY

Hippocampal CA1 cells possess several varieties of long-lasting synapt ic plasticity: two different forms of long-term potentiation (LTP) and at least one form of long-term depression (LTD). All forms of synapti c plasticity are induced by afferent activation, all involve Ca2+ infl ux, all can be blocked by Ca2+ chelators, and all activate Ca2+-depend ent mechanisms. The question arises as how different physiological res ponses can be initiated by activation of the same second messenger. We consider two hypotheses which could account for these phenomena: volt age-dependent differences in cytosolic Ca2+ concentration acting upon Ca2+ substrates of differing Ca2+ affinities and compartmentalization of the Ca2+ and its substrates. (C) 1994 Wiley-Liss, Inc.