Fig. 8.

Presynaptic depression of release unmasked facilitation. (A) Dopamine IPSCs were measured subsequent to three patterns of discharge activity: a train of five stimuli alone (5), a train preceded by one prepulse (1, 5) and a train preceded by three prepulses (1, 1, 1, 5). A single prepulse was sufficient to depress release and the amplitude of the IPSC. (B) Summarized data suggest that, subsequent to a prepulse, the IPSC produced by a single pulse was much more depressed than the IPSC produced by a train. (C) As this IPSC (‘5 stims’) is more than the arithmetic summation of five single-pulse IPSCs (‘5 × 1 stim’), presynaptic depression may be in effect unmasking the facilitation of release.