PRESYNAPTIC COMPONENT OF LONG-TERM POTENTIATION VISUALIZED AT INDIVIDUAL HIPPOCAMPAL SYNAPSES

Long-term potentiation has previously been studied with electrophysiol ogical techniques that do not readily separate presynaptic and postsyn aptic contributions. Changes in exocytotic-endocytotic cycling have no w been monitored at synapses between cultured rat hippocampal neurons by measuring the differential uptake of antibodies that recognize the intraluminal domain of the synaptic vesicle protein synaptotagmin. Ves icular cycling increased markedly during glutamate-induced long-term p otentiation. The degree of potentiation was heterogeneous, appearing g reater at synapses at which the initial extent of vesicular turnover w as low. Thus, changes in presynaptic activity were visualized directly and the spatial distribution of potentiation could be determined at t he level of single synaptic boutons.