Figure 6.
Dynamic [Ca2+]i changes in response to cocaine (8 mg/kg, i.p.) in the striatum of D2R-EGFP mice without (a) and with (b) raclopride (D2 antagonist) pretreatment. 1, 2, [Ca2+]i images at baseline and t = 25 min after cocaine injection. 3, EGFP images of D2R. 4, Ca2+ and EGFP images overlapped to identify [Ca2+]i from D2R neurons. 5, Δ[Ca2+]i from individual D2R neurons (dark solid curves) and their averaged change (blue bold curve), and from non-D1R cells (dashed curves). Cocaine-evoked [Ca2+]i decrease was continuous over t > 30 min. The dark bold curve correspond to the control study following saline injection. 6, Δ[Ca2+]i image at t = 25 min. Cocaine-evoked a significant [Ca2+]i decrease (−9.0 ± 1.5%, n = 23, p < 0.0001) in D2R neurons which was effectively inhibited by D2 antagonist down to (−1.7 ± 1.3%, n = 27, p < 0.0001).