(A)Left, Example trace of isolated sodium leak current in wildtype dopamine neuron recorded at −70 mV in 2 mM Ca2+ and 0.1 mM Ca2+, followed by bath application of 100 µM dopamine and subsequent substitution of Na+ with NMDG. Right, Summary plot of data in different conditions. (B) Example trace of isolated sodium leak current in NALCN cKO mice. Note, dopamine inhibition of sodium leak is abolished. (C) Left, Example traces showing inhibition of sodium leak current induced by 100 nM (n = 5), 1 μM (n = 3), 10 μM (n = 3), and 300 μM (n = 4) dopamine followed by block of leak current in NMDG solution. Traces have been normalized to control current amplitude. Right, Concentration-response curve for inhibition of leak current by dopamine. (D) Example trace of leak current in β-arrestin2 KO mice. Right, Summary plot. (E) Left, Example trace of the isolated sodium leak current recorded with GDP-βS added to internal solutions. Dopamine applied to cell in 2 mM Ca2+ external solutions. Note the slow increase in leak current with GDP-βS internal. Right, Summary plot. (F) Example trace of sodium leak current with GDP-βS internal solution. Dopamine applied to cell in 0.1 mM Ca2+ external solutions. Right, Summary plot of data. (G) Summary plot of data shown in A, B, D and E. (H) Bar plot of the dopamine-sensitive current shown in A, B, D and E. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.001.