Electrophysiological properties of neurons in the robust nucleus of the arcopallium of adult male zebra finches

Nucleus robust arcopallium (RA) of the songbird is a distinct forebrain region that is essential for song production. To explore the electrophysiological properties, whole cell recordings were made from adult zebra finch RA neurons in slice preparations. Based on the electrophysiological properties, neurons in RA were classified into two distinct classes. Type I neurons were spontaneously active. They had larger input resistance, longer time constant, larger time-peak of an afterhyperpolarization (AHP), and broader action potentials than those of the other class. A slow, time-dependent inward rectification was induced by hyperpolarizing current pulses in this type of neuron, and was blocked by external CsCl (2 mM). Type II neurons had a more negative resting membrane potential than that of type I neurons. They were characterized by a steeper slope of the recovery from the peak of the AHP and frequency–current relationships, a higher firing threshold, and irregular spiking in response to depolarizing current injection.

Research highlights▶ Type I (a and b) and II neurons were classified in nucleus robust arcopallium. ▶ Type I neurons had larger IR, longer τ, larger time-peak of an AHP and broader APs. ▶ CsCl blocked the inward rectification induced by hyperpolarizing current pulses. ▶ Type II neurons had a steeper slope of AHP and I–f curve, a larger firing threshold. ▶ Type I and II neurons in RA may play distinct roles in song production.