IClamp

IClamp, short for intracellular current clamp, is a method used to inject a controlled electrical current into a cell while recording the membrane potential. In electrophysiology, it is employed to study cellular excitability, evoked and spontaneous firing, and the input–output properties of neurons and other excitable cells. By delivering precise current pulses, researchers can elicit action potentials, explore subthreshold responses, and determine parameters such as rheobase and firing patterns.

In experimental setups, a microelectrode or patch pipette injects current across the cell membrane through a circuit that defines the amplitude, duration, and onset time of the current relative to a clock. The resulting voltage trace reflects the cell’s passive properties and the dynamics of ion channels, though measurements can be affected by electrode resistance and other artifacts.

In computational neuroscience, IClamp denotes a model component that injects current into a simulated compartment at a specified location and time. In the NEURON simulation environment, IClamp is a point process with adjustable parameters including amp (amplitude of injected current, typically in nanoamperes), delay (time before onset, in milliseconds), and dur (duration of injection, in milliseconds). By varying these parameters, researchers can probe neuronal responsiveness and generate controlled voltage responses for modeling studies.

Compared with voltage clamp, which fixes membrane potential and measures current, IClamp controls current and observes the resulting voltage. Related techniques include dynamic clamp, patch clamp, and other electrophysiological methods.