Figure 6.

Assessment of dopamine release following β-catenin deletion in DA neurons. (A) Input–output relationship for DA release elicited by single-pulse (1-msec duration) stimulation in striatal slices from control (WT) and DA-βcat KO mice (KO). No significant differences were observed. (B) Decay time constants of DA signals were not significantly different between control (WT) and KO mice, indicating that DA transporter-mediated uptake is not affected by gene deletion. (C) Voltammetric recording traces from a control and knockout mouse in which successive pulses ([S1] black arrow, [S2] gray arrow) were given at varying interstimulus intervals. Summary plot shows the time to recovery of the second pulse amplitude to the first pulse (S2/S1). No significant differences were observed between WT and KO mice, suggesting that recovery times for DA release were not impaired by β-catenin deletion. (D) Voltammetric recording traces of the first (black) and tenth (gray) stimulation of a 10-pulse train delivered at lower (0.05 Hz) and higher (0.33 Hz) frequencies. Note the slightly greater depression of the response in the DA-βcat KO mice. Summary plot shows the frequency-dependent decline in signal amplitude in WT and KO mice. Slices from DA-βcat KO mice showed a significantly faster rate of decline (τ, 0.269 Hz) than control mice (τ, 0.189 Hz; F_(1,163) = 25.26, P < 0.01).