Persistent inward current (PIC)

Persistent inward currents (PICs) are intrinsic, voltage-dependent ionic currents, predominantly mediated by L-type calcium channels (CaV1.3) and persistent sodium channels (NaV1.6). PICs can convert transient synaptic inputs into prolonged depolarization and self-sustained neuronal firing, thus dramatically amplifying motoneuron excitability and enabling rhythmic and continuous motor output essential for movement and posture. They are strongly regulated by neuromodulators such as serotonin and norepinephrine, and contribute to phenomena like spasticity and exaggerated reflexes after spinal cord injury, as well as to motoneuron degeneration in diseases like ALS. PICs are a functional neurophysiological concept, not a single druggable molecular target, though drugs acting on their underlying channels can modulate them in clinical and experimental contexts.

Other names

Persistent Na\(^+\) currentPersistent Ca\(^{2+}\) currentPICsplateau currents

Blockade of L-type Ca\(^{2+}\) channels reduces CaPIC; blockade of persistent Na\(^+\) channels reduces NaPIC; modulation by monoamines enhances PIC amplitude through second-messenger signaling.