Voltagedependent

Voltagedependent, often written with a hyphen as voltage-dependent, is an adjective used in biology, biophysics, and neuroscience to describe a property or process that changes with membrane potential or an applied electric field. It denotes a relationship in which the rate, probability, or outcome depends on voltage rather than being constant.

In physiology, voltage dependence is most familiar in ion channels. Voltage-dependent channels alter their conformation in response to changes in membrane potential, thereby changing their conductance. A typical mechanism involves a voltage-sensing domain, such as the S4 segment in many voltage-gated channels, which moves gating charges in response to depolarization. This movement can open activation gates or inactivate channels, shaping electrical signals like action potentials. The concept is central to the Hodgkin-Huxley model, which uses voltage-dependent gating variables to describe how sodium and potassium currents regulate neuronal excitability.

Voltage dependence is described quantitatively by activation and inactivation curves that relate channel state probabilities to voltage. Common mathematical forms include Boltzmann-type expressions and other sigmoidal relationships. Experimental methods such as voltage-clamp and patch-clamp help measure these dependencies, while pharmacology uses blockers to dissect the contributions of specific voltage-dependent channels.

Beyond classic ion channels, voltage dependence can appear in other biological contexts, including regulation of certain enzymes, calcium release pathways, and electro-responsive transport processes. Distinctions are sometimes made between voltage dependence (a general sensitivity to voltage) and voltage gating (a mechanism that transitions between states in response to voltage).