Figure 5. SP inhibits baclofen-mediated currents onto VTA neurons.
A, average holding current change in response to 20 μm baclofen before and during bath application of SP (1 μm). Individual experiments are normalized so that the peak of the initial baclofen application is 100%. Responses are re-zeroed prior to 2nd baclofen application for comparison (hash marks on x-axis indicate the point of renormalization). B, application of baclofen 10 min after washout of SP shows that the inhibition of the baclofen current by SP reverses. C, control experiments showing that multiple applications of baclofen do not display desensitization when applications are separated by 20 min. D, summary data for control (n= 4), SP experiments (n= 5), and following washout of SP (n= 5). *P < 0.05 compared to control, one-way ANOVA with a Holm–Sidak post-hoc test.