Fig. 6.

Effect of CdCl₂ on paired-pulse facilitation before and after injection of apRab3-Q80L.A, In this typical experiment, neurotransmitter release from two neurons was followed in the presence of control medium (condition 1), in presence of 200 μmCdCl₂ (denoted by the horizontal bar in conditions 2 and 3), and after washing out CdCl₂ (condition 4). In addition, one neuron (•) was injected with apRab3-Q80L (arrow,Q80L; conditions 3 and4). B, For the neuron identified by • (i.e., the one injected by apRab3-Q80L), paired-pulse facilitation (mean ± SD) was determined at a 40 msec interpulse interval in the four experimental conditions described inA. Asterisk denotes p< 0.001 when the amplitude of facilitation is compared with any other condition. C, Typical recordings of paired postsynaptic responses recorded in the four experimental conditions described inA. For comparison, postsynaptic responses were normalized against the amplitude of the first response in the pair. Note that decay times of postsynaptic responses were shorter in CdCl₂; this was taken into account for determining paired-pulse facilitation (see Materials and Methods).