Fig. 3

Synaptic transmission and SB uptake at hippocampal synapses. a–f Simultaneous electrophysiological and optical recording from a pair of synaptically connected hippocampal neurons (representative experiment from N = 5 pairs). a Images of the pre-synaptic and post-synaptic cells (left, DIC image; middle, in green GZ expression in the presynaptic cell; right, merge). b Evoked trains of action potentials in the presynaptic neuron (top traces) and the corresponding synaptic currents in the postsynaptic cell (lower traces) at two stimulation frequencies (25 and 40 Hz, 10 action potentials per train; trains applied every 5 s). c A subset of synapses, to illustrate reporter expression (GZ) and the effect of action potential trains on SB uptake (SB). d Analysis of the strength of synaptic transmission at different presynaptic stimulation frequencies (20–40 Hz trains as in b), indicating facilitation of EPSC amplitude. e Time-course of SB uptake (normalized for its final value) for N = 18 synapses belonging to the same axon at variable stimulation frequencies. f Percent increment of SB uptake for individual trains and synapses (synaptic charge and SB uptake were averaged over trains at the same stimulation frequency; same synapses shown in e). The green line is the fitting trace with a mono-exponential curve. Notice that the correlation approaches a ceiling for very high postsynaptic current values. Scale bars: 20 µm (a), 10 mV or 25 pA, 100 ms (b), 5 µm (c)