K(+) currents in cultured neurones from a polyclad flatworm

Area of Science:

• Neuroscience
• Cellular Electrophysiology
• Marine Biology

Background:

• Understanding neuronal excitability is crucial for deciphering nervous system function.
• Potassium (K+) currents are fundamental in regulating neuronal membrane potential and action potential firing.
• Comparative studies across diverse animal phyla reveal conserved and divergent mechanisms of neuronal excitability.

Purpose of the Study:

• To characterize the electrophysiological properties of potassium currents in the brain of the polyclad flatworm Notoplana atomata.
• To investigate the pharmacological and voltage-dependence properties of these currents.
• To compare the identified K+ currents with known K+ channel families in other organisms.

Main Methods:

• Primary cell culture of Notoplana atomata brain cells.
• Whole-cell patch-clamp electrophysiology to record K+ currents.
• Pharmacological analysis using tetraethylammonium and 4-aminopyridine.
• Voltage-clamp protocols to determine activation, inactivation, and recovery kinetics.

Main Results:

• Two distinct outwardly directed K+ currents were identified: one rapidly activating and inactivating, the other rapidly activating without inactivation.
• Both currents activated over similar voltage ranges, with significantly right-shifted activation and inactivation properties compared to typical Shaker-like currents.
• The inactivating current was selectively blocked by 4-aminopyridine, while both currents were insensitive to tetraethylammonium.

Conclusions:

• The identified K+ currents in Notoplana atomata exhibit unique characteristics, differing from most previously reported A-type K+ currents.
• These novel K+ currents, particularly the rapidly inactivating component, share similarities with certain cnidarian, mollusc, and vertebrate Kv3 channels.
• The distinct properties of these K+ currents suggest they play novel roles in shaping the excitability of Notoplana atomata neurons.