Figure 5.

Pentobarbitone inhibits the calcium transients recorded from synaptic boutons. Panel a shows a single optical section of the labelled structures. The arrow indicates the position of the varicosity. (b) shows the calcium transients recorded from this synaptic bouton before, during and after exposure to 150 μM pentobarbitone. The dashed line indicates the prestimulus baseline. (c) shows the action potentials used to evoke the calcium transients shown in (b). The calcium transients were reversibly depressed by 150 μM pentobarbitone. Although the overshoot of the action potential was reduced during the wash, it was still sufficient to elicit a calcium transient comparable in amplitude to that seen in the control period. Note the expanded time base for the action potential records.