title: Reduction in potassium currents in identified cutaneous afferent dorsal root ganglion neurons after axotomy.
abstract: Potassium currents have an important role in modulating neuronal excitability. We have investigated the effects of axotomy on three voltage-activated K(+) currents, one sustained and two transient, in cutaneous afferent dorsal root ganglion (DRG) neurons. Fourteen to 21 days after axotomy, L(4) and L(5) DRG neurons were acutely dissociated and were studied 2-8 h after plating. Whole cell patch-clamp recordings were obtained from identified cutaneous afferent neurons (46-50 microm diam); K(+) currents were isolated by blocking Na(+) and Ca(2+) currents with appropriate ion replacement and channel blockers. Separation of the current components was achieved on the basis of sensitivity to dendrotoxin or 4-aminopyridine and by the response to variation in conditioning voltage. Both control and injured neurons displayed qualitatively similar complex K(+) currents composed of distinct kinetic and pharmacological components. Three distinct K(+) current components, a sustained (I(K)) and two transient (I(A) and I(D)), were identified in variable proportions. However, total peak current was reduced by 52% in the axotomized cells when compared with control cells. Two current components were reduced after ligation, I(A) by 60%, I(K) by over 65%, compared with control cells. I(D) appeared unaffected after acute ligation. These results indicate a large reduction in overall K(+) current, resulting from reductions in I(K) and I(A), on large cutaneous afferent neurons after nerve ligation and have implications for excitability changes of injured primary afferent neurons.
authors.affiliation: Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors.forename: B
authors.initials: B
authors.lastname: Everill
authors.forename: J D
authors.initials: JD
authors.lastname: Kocsis
mesh_terms: D000818:Animals; D019771:Axotomy; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000294:innervation*
chemical_list: D015221:Potassium Channels