title: Increased Na+ and K+ currents in small mouse dorsal root ganglion neurons after ganglion compression.
abstract: We investigated the effects of chronic compression (CCD) of the L3 and L4 dorsal root ganglion (DRG) on pain behavior in the mouse and on the electrophysiological properties of the small-diameter neuronal cell bodies in the intact ganglion. CCD is a model of human radicular pain produced by intraforaminal stenosis and other disorders affecting the DRG, spinal nerve, or root. On days 1, 3, 5, and 7 after the onset of compression, there was a significant decrease from preoperative values in the threshold mechanical force required to elicit a withdrawal of the foot ipsilateral to the CCD (tactile allodynia). Whole cell patch-clamp recordings were obtained, in vitro, from small-sized somata and, for the first time, in the intact DRG. Under current clamp, CCD neurons exhibited a significantly lower rheobase compared with controls. A few CCD but no control neurons exhibited spontaneous action potentials. CCD neurons showed an increase in the density of TTX-resistant and TTX-sensitive Na(+) current. CCD neurons also exhibited an enhanced density of voltage-dependent K(+) current, due to an increase in delayed rectifier K(+) current, without a change in the transient or "A" current. We conclude that CCD in the mouse produces a model of radicular pain, as we have previously demonstrated in the rat. While the role of enhanced K(+) current remains to be elucidated, we speculate that it represents a compensatory neuronal response to reduce ectopic or aberrant levels of neuronal activity produced by the injury.
authors.affiliation: Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
authors.forename: Ni
authors.initials: N
authors.lastname: Fan
authors.forename: Parul
authors.initials: P
authors.lastname: Sikand
authors.forename: David F
authors.initials: DF
authors.lastname: Donnelly
authors.forename: Chao
authors.initials: C
authors.lastname: Ma
authors.forename: Robert H
authors.initials: RH
authors.lastname: Lamotte
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D005727:Ganglia, Spinal / Q000187:drug effects / Q000503:physiopathology*; D006930:Hyperalgesia / Q000188:drug therapy / Q000503:physiopathology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D010146:Pain / Q000188:drug therapy / Q000503:physiopathology; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000502:physiology; D011843:Radiculopathy / Q000188:drug therapy / Q000503:physiopathology*; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D024642:Potassium Channels, Voltage-Gated; D015222:Sodium Channels; D013779:Tetrodotoxin