Characteristics of the electrical response to dopamine in neuroblastoma cells

1. The characteristics of the electrical response to dopamine in the mouse neuroblastoma cell line N1E-115 were studied. 2. Neuroblastoma cells responded to ionophoretically applied dopamine by generating a transient depolarization. Under voltage-clamp conditions, a transient inward current was recorded in response to dopamine application. 3. The receptor was more effectively activated by dopamine than by noradrenaline. Haloperidol blocked the dopamine-induced current with an apparent dissociation constant of 40 nM. Phentolamine was much less potent than haloperidol, and propranolol had no effect. 4. The dopamine-induced current was increased in amplitude by hyperpolarizing the membrane, decreased by depolarization, and reversed its polarity at + 14 mV. 5. When the external sodium concentration was decreased from 125 to 94 mM, the reversal potential was shifted in the direction of hyperpolarization by 10 mV. 6. Increasing the external potassium concentration from 0.2 to 20 mM caused a shift of the reversal potential by 13 mV in the direction of depolarization. 7. Replacement of external chloride with isethionate or glutamate caused little or no shift in the reversal potential, but increased the amplitude of the current. 8. Increase in external calcium concentration caused a block of the dopamine-induced current with an apparent dissociation constant of 1.3 mM, without altering its reversal potential. 9. It is concluded that the ionic channel activated by dopamine undergoes a conductance increase to both sodium and potassium but not to chloride or calcium.