MOLECULAR AND FUNCTIONAL DIVERSITY AT SYNAPSES OF INDIVIDUAL NEURONS IN-VITRO

We have quantified activity-dependent uptake of the fluorescent dye FM 1-43 in combination with immunocytochemistry for synaptic vesicle-asso ciated proteins (SVPs) at individual synapses in primary cultures of r at cortical neurons. We show that expression of synaptic proteins is h ighly variable and that the levels of synaptophysin (p38), synapsin I and sv2, but not synapsin II, correlate with the extent of FM1-43 labe lling at synapses. The data indicate that SVP levels affect the uptake of FM1-43 with different efficacy (p38 > synapsin I > sv2 or synapsin II). We also found that the relative levels of SVPs vary at individua l boutons of single neurons grown in isolation, which indicates that d ifferential regulation of specific SVPs may contribute to the selectiv e modulation of activity at synapses of the same neuron.