Sodium pump evokes high density pump currents in rat midbrain dopamine neurons

Area of Science:

• Neuroscience
• Electrophysiology
• Cellular Physiology

Background:

• The sodium-potassium ATPase (Na+/K+-ATPase) is crucial for maintaining ion gradients in neurons.
• Its activity is essential for neuronal excitability and function, particularly in dopamine neurons.

Purpose of the Study:

• To investigate the relationship between intracellular sodium concentration and sodium pump current in dopamine neurons.
• To determine the role of the sodium pump in regulating neuronal activity.

Main Methods:

• Whole-cell voltage clamp recordings were performed on dopamine neurons in rat substantia nigra and ventral tegmental area slices.
• Varying concentrations of intracellular sodium ([Na+]pip) and extracellular potassium ([K+]o) were used.
• Strophanthidin-sensitive currents were measured to assess sodium pump activity.

Main Results:

• Strophanthidin-evoked currents, indicative of sodium pump activity, increased with higher intracellular sodium concentrations.
• The half-maximal effective concentration (EC50) for strophanthidin was approximately 7.1 µM, and the pump current was half-maximal at [Na+]pip of 1.3 mM.
• Maximum pump current was estimated at 830 pA, and was sensitive to extracellular potassium levels.

Conclusions:

• Intracellular sodium loading leads to substantial sodium pump currents in dopamine neurons.
• The sodium pump plays a significant physiological role in the burst firing of midbrain dopamine neurons.