Chelation of postsynaptic Ca2+ facilitates long-term potentiation of hippocampal IPSPs.

In guinea pig hippocampal slices, a tetanic stimulation of the stratum radiatum caused long-term potentiation (LTP) of the excitatory postsynaptic potential (EPSP) but not of the GABAB receptor-mediated slow inhibitory postsynaptic potential (IPSP) in the CA1 neurons. In neurons in which Ca2+ was chelated with 1,2-bis(2-aminophenoxy) ethane N,N,N',N'-tetra-acetic acid (BAPTA) or ethylene-bis(oxyethylenenitrilo)tetra-acetic acid (EGTA), tetanic stimulation of the stratum radiatum caused LTP of the slow IPSP but not of the EPSP. These results indicate that a reciprocal relationship exists between LTP of the EPSP and LTP of the slow IPSP as far as the involvement of the postsynaptic Ca2+ is concerned.