Figure 3.
Activation of CB1 receptors does not affect the time course of presynaptic calcium influx. Fluorescence changes evoked by single stimuli were measured with the calcium-sensitive indicator magnesium green and a photodiode with a response time of 3 kHz. A, The effects of WIN55,212-2, AM251, and TEA on both the peak ΔF/F signal (left) and on the time course measured during the indicated times (right) are shown for a representative experiment. In addition, the presynaptic volley was monitored (B) at the times indicated in A (left). B, The presynaptic volley is shown under control conditions (left) and in the presence of WIN55,212-2 (middle, black trace) or TEA (right, black trace) as compared with the volley under control conditions (middle and right, gray traces). C, The derivative of the fluorescence transient indicates the time course of presynaptic calcium influx corresponding to ICa under control conditions (left) and in the presence of WIN55,212-2 (middle) or TEA (right). D, The time courses of presynaptic calcium influx measured in the presence of WIN55,212-2 (left, bold trace) and in the presence of TEA (right, bold trace) are normalized and compared with control traces (left and right, thin traces).