Two-photon laser scanning microscopic (TPLSM) images of FM1-43 vesicular release from Schaffer collateral terminals in field CA1 of hippocampal slices confirm that release probability is reduced by chronic Pb²⁺ exposure.

<p>(A) Representative TPLSM pseudocolor images of FM1-43 loaded presynaptic terminals in <i>stratum radiatum</i> of field CA1 in hippocampal slices from Pb^<b>2+</b>-treated and control rats imaged prior to (0 min) and after 8 minutes (8 min) of 2Hz Schaffer collateral stimulation (Calibration Bar: 5 μm). (B) Time course (Mean ± SEM) of stimulus-evoked FM1-43 destaining from puncta in field CA1 of hippocampal slices in response to 2Hz Schaffer collateral stimulation (solid bar) in control (black circles, N = 8 slices, 35 puncta) versus Pb^<b>2+</b>-treated (red circles, N = 6 slices, 30 puncta) rats. (C) Mean ± SEM of initial decay time constant (left bars) and ending residual fluorescence (right bars) in the slices in (B) from control (CTL) versus Pb^<b>2+</b>-treated (LEAD) rats (*,<i>P</i> <0.05, Student’s t-test), showing slower destaining of Schaffer collateral terminals from rats chronically exposed to Pb^<b>2+</b>.