Figure 6.

M₄Rs (and not M₂Rs) are required for mAChR control of DA release in NAc core. a–d, Mean peak [DA]_o ± SEM versus frequency in NAc core during four pulse trains (1–100 Hz) in control conditions (filled circles) or Oxo-M (unfilled) or Oxo-M plus DHβE (gray fill) normalized to [DA]_o released by a single pulse in control conditions (left) or own condition (right), in wild types (WT) (a), M₅R-knock-outs (M₅R KO) (b), M₂R-knock-outs (M₂R KO) (c), and M₄R-knock-outs (M₄R KO) (d) (n = 9–12). The asterisks indicate significance level in post hoc t tests for Oxo-M versus controls: *p < 0.05, ***p < 0.001. The daggers indicate significance level in post hoc t tests for Oxo-M versus Oxo-M plus DHβE: ^†††p < 0.001. Significance levels for comparison of Oxo-M plus DHβE versus control, or for data in right-hand panels, are omitted for clarity. a–c, In wild types, M₅R-KO, or M₂R-KO, Oxo-M significantly modifies evoked [DA]_o in an activity-dependent manner and additional application of DHβE does not modify evoked [DA]_o further (n = 9–12). d, In M₄R-KO, Oxo-M does not modify evoked [DA]_o, but subsequent addition of DHβE modifies [DA]_o in a marked and significant, activity-dependent manner (n = 12).