Differential blockade of neuronal voltage-gated Na(+) and K(+) channels by antidepressant drugs.
The effects of a range of antidepressants were investigated on neuronal voltage-gated Na(+) and K(+) channels. With the exception of phenelzine, all antidepressants inhibited batrachotoxin-stimulated 22Na(+) uptake, most likely via negative allosteric inhibition of batrachotoxin binding to neurotoxin receptor site-2 on the Na(+) channel. Imipramine also produced a differential action on macroscopic Na(+) and K(+) channel currents in acutely dissociated rat dorsal root ganglion neurons. Imipramine produced a use-dependent block of Na(+) channels. In addition, there was a hyperpolarizing shift in the voltage-dependence of steady-state Na(+) channel inactivation and slowed repriming kinetics consistent with imipramine having a higher affinity for the inactivated state of the Na(+) channel. At higher concentrations, imipramine also blocked delayed-rectifier and transient outward K(+) currents in the absence of alterations to the voltage-dependence of activation or the kinetics of inactivation. These actions on voltage-gated ion channels may underlie the therapeutic and toxic effects of these drugs.
D000465:Algorithms; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology; D001496:Batrachotoxins / Q000378:metabolism; D001667:Binding, Competitive / Q000187:drug effects; D004594:Electrophysiology; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D007099:Imipramine / Q000494:pharmacology; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects*; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D009498:Neurotoxins / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D000928:Antidepressive Agents; D000929:Antidepressive Agents, Tricyclic; D001496:Batrachotoxins; D009498:Neurotoxins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D012964:Sodium; D007099:Imipramine