Cation current activated by hyperpolarization (IH) in guinea pig enteric neurons.

Area of Science:

• Neuroscience
• Electrophysiology
• Gastrointestinal Physiology

Background:

• The enteric nervous system (ENS) controls gastrointestinal function.
• Understanding ion channel activity in enteric neurons is crucial for elucidating ENS function.
• Previous research has identified various currents in enteric neurons, but a specific inward current in AH neurons remained uncharacterized.

Purpose of the Study:

• To characterize a novel inward current (IH) in guinea pig myenteric AH neurons.
• To investigate the ionic basis and properties of IH.
• To determine the functional role of IH in myenteric AH neurons.

Main Methods:

• Intracellular microelectrode and whole-cell patch-clamp recordings were performed on guinea pig enteric neurons in vitro.
• Step hyperpolarizations were used to evoke and analyze the inward current (IH).
• Ionic substitutions (sodium, potassium) and pharmacological agents (cesium, cobalt, barium) were employed to probe the current's properties.

Main Results:

• A voltage-dependent inward current (IH) was observed in most myenteric AH neurons, activated by hyperpolarization and peaking around -100 mV.
• IH exhibited a reversal potential around -40 mV, was dependent on extracellular sodium, and was modulated by extracellular potassium.
• Cesium blocked IH in a voltage-dependent manner, increasing spike after-hyperpolarization, while cobalt and barium had no effect.

Conclusions:

• The study identified and characterized a novel inward current (IH) in myenteric AH neurons.
• IH is likely carried by a non-selective cation conductance, distinct from known currents.
• In myenteric AH neurons, IH counteracts the persistent calcium-activated potassium current, contributing to resting potential stabilization.