Persistent Ca2+ current contributes to a prolonged depolarization in Aplysia bag cell neurons

Area of Science:

• Neuroscience
• Cellular Electrophysiology

Background:

• Neurons alter excitability to initiate behavior or store information.
• Bag cell neurons in Aplysia exhibit prolonged depolarization after stimulation, inducing reproduction.

Purpose of the Study:

• Investigate the mechanisms sustaining prolonged depolarization in bag cell neurons.
• Test the hypothesis of a voltage-dependent persistent calcium (Ca2+) current.

Main Methods:

• Primary culture of bag cell neurons under voltage clamp.
• Utilized calcium (Ca2+) and barium (Ba2+) as permeant ions.
• Applied nickel (Ni2+) to assess current sensitivity.
• Examined protein kinase C activation effects.

Main Results:

• Identified a persistent Ca2+ current activating around -40 to -50 mV with slow decay.
• This persistent current, like the rapid Ca2+ current, was Ni2+ sensitive and enhanced by Ba2+.
• Protein kinase C activation enhanced both rapid and persistent Ca2+ currents, prolonging depolarization.

Conclusions:

• Prolonged depolarization results from a synergistic interplay of Ca2+ influx, a cation current, and a persistent voltage-dependent Ca2+ current.
• This current synergy is modulated and may be a common mechanism for activity-dependent excitability changes.