Figure 2.
μ-Opioid receptor effects on single and burst stimulation induced DA overflow, as well as short-term presynaptic facilitation of DA overflow. a, Effect of the number of 25 Hz stimulus pulses on peak DA overflow under control conditions and after treatment with EM-1, deltorphin II, or nicotine (n = 24, 24, 6, 8, respectively). b, DA responses to single and 25 Hz paired pulses demonstrate EM-1-induced transformation of paired-pulse depression to paired-pulse facilitation. P2 is calculated by subtracting P1 from P1 + P2. c, Paired-pulse ratios in control conditions and in the presence of 1 μm EM-1, deltorphin II, or nicotine (n = 24, 6, 8, respectively). A one-way ANOVA followed by Fisher's PLSD post hoc test found the control condition was significantly different from each drug condition (F(3,57) = 6.7, *p < 0.02).