| I Sodium | | |
| I Na,t | "Transient"; rapidly inactivating | Action potentials |
| I Na,p | Persistent (plateau); non-inactivating; TTX-resistant | Enhances depolarizations; contributes to steady-state firing |
| I Potassium | | |
| I A, slow | Slowly inactivating "delay" current I K(D) | Similar to A-type current but inactivates slowly (seconds). Participates in spike repolarization. |
| I A | "Transient"; inactivating | Delayed onset of firing; interspike interval; action potential repolarization |
| I K,leak | Contributes to neuronal resting "leak"conductance | Helps determine resting membrane potential |
| I M | Activated by depolarization above -65 mV; slow, weak and non-inactivating; blocked by ligands like acetylcholine acting through muscarinic (M) receptors | Contributes to slow spike frequency adaptation |
| I K | Activated by strong depolarization; delayed rectifier | Repolarization of action potential |
| I Calcium | | |
| I L high threshold | "Long-lasting"; slowly inactivating; threshold around -20 mV | Underlies Ca2+ spikes that are prominent in dendrites; involved in synaptic transmission |
| I N | "Neither"; rapidly inactivating; threshold around -20 mV | Underlies Ca2+ spikes that are prominent in dendrites; involved in synaptic transmission |
| I p,q | Includes both p-type and q-type currents | |
| I T low threshold | "Transient"; rapidly inactivating, threshold negative to -65mV | Underlies rhythmic burst firing; some dendritic action potentials |
| I Chloride | | |
| I Cl,Ca | Calcium activated chloride current | Can enhance or decrease response depending on the Cl- equilibrium potential |
| I Mixed | | |
| I K,Ca | Includes BK, IK, SK, and I AHP currents; K current activated by increases in [Ca2+]i; voltage dependence varies | Action potential repolarization and interspike interval |
| I CNG | Cyclic-Nucleotide Gated nonspecific cation channel | Dark current in photoreceptors, activated by cGMP; light response in ON retinal bipolar cells; receptor current in olfactory sensory neurons, activated by cAMP, modulated by cGMP; found widely in CNS neurons |
| I h | Inward rectifier; "Queer"; activated by hyperpolarization/mixed cation current | Prevents strong hyperpolarization; increases membrane resistance during membrane depolarization |
| I CAN | Calcium Activated Nonspecific cation channel | |