The effect of dopamine on Δψ_m and [Ca²⁺]_c in midbrain neurons and astrocytes.

<p>a: Dopamine 20 µM induces a modest rise in [Ca²⁺]_c in wt neurons and astrocytes, as measured by fura-2 ratio. There are no associated changes in Δψ_m, as measured by Rhodamine 123 fluorescence. Depolarisation of the plasma membrane using 50 mM KCl induces opening of voltage sensitive calcium channels and a further rise in [Ca²⁺]_c, with no change in ΔΨ_m. b: Dopamine 20 µM induces a larger rise in [Ca²⁺]_c in PINK1 ko cells. Furthermore this increase in [Ca²⁺]_c is associated with a reduction in ΔΨ_m. Application of 50 mM KCl induces a further rise in [Ca²⁺]_c and profound mitochondrial depolarisation. Figure bi demonstrates the increase in Rh123 fluorescence at 1 minute, 6 minutes and 12 minutes that reflects mitochondrial membrane depolarisation in PINK1 ko cells. c, d: Single cell traces of PINK1 ko neurons demonstrating that dopamine induced decrease in ΔΨ_m occurs independently of any change in [Ca²⁺]_c in some cells (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037564#pone-0037564-g001" target="_blank">Figure 1c</a>), whereas in other cells dopamine induced decrease in ΔΨ_m co-incides with a rise in [Ca²⁺]_c (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0037564#pone-0037564-g001" target="_blank">Figure 1d</a>). e: Incubation with D1/D5 receptor antagonist SCH23390 (20 µM) did not alter the dopamine induced calcium signal or mitochondrial depolarisation in PINK1 ko neurons. f: Dopamine induced mitochondrial depolarisation was prevented by application of the PTP inhibitor 1 µM cyclosporine A.