Figure 2.

High concentrations of dopamine increase paired-pulse facilitation. (a) Pairs of stimulation pulses with a 30 millisecond interpulse interval were delivered before and after 5-minute bath application of 50 μM dopamine. Averaged traces at left show responses recorded before (ACSF) and after (DA) dopamine from a representative cell. Note the suppression of the response to the first pulse and the large facilitation of the second response following dopamine (dotted line). Traces at right have been scaled to the amplitude of the first response in normal ACSF to aid comparison. Group data are shown on the right. (b) Paired-pulse facilitation was also enhanced by 10 μM dopamine. (c) In contrast, the low concentration of 1 μM dopamine does not affect paired-pulse ratio.