BK-Type K(Ca) channels in two parasympathetic cell types: differences in kinetic properties and developmental...

Area of Science:

• Neuroscience
• Electrophysiology
• Ion Channel Biology

Background:

• Chick ciliary ganglion neurons originate from a common precursor but innervate distinct targets, leading to different electrical properties.
• Large-conductance calcium-activated potassium channels (BK-type KCa) are crucial for regulating neuronal firing patterns and action potential waveforms.

Purpose of the Study:

• To investigate the differences in plasma membrane ionic channels, specifically BK-type KCa channels, between choroid and ciliary neurons.
• To determine the developmental stages at which these neuronal subtypes diverge in their channel expression and function.

Main Methods:

• Patch-clamp recording techniques were employed to examine the intrinsic electrical properties of identified choroid and ciliary neurons.
• Steady-state fluctuation analyses and single-channel recordings were used to characterize the kinetic properties of BK-type KCa channels.
• In vitro development and target tissue extract analysis were performed to investigate the regulation of KCa channel expression.

Main Results:

• Both neuron types express robust BK-type KCa currents, but kinetic properties differ significantly, with slower gating observed in choroid neurons.
• Single-channel recordings confirmed a longer mean open-time for KCa channels in choroid neurons compared to ciliary neurons.
• Functional KCa channel expression in ciliary neurons requires target-derived trophic factors, whereas choroid neurons do not exhibit this dependency.

Conclusions:

• Distinct kinetic properties of BK-type KCa channels contribute to the differential electrical phenotypes of chick choroid and ciliary neurons.
• Target-derived trophic factors differentially regulate the developmental expression of functional KCa channels in these two neuronal populations.