Spinal cord stimulation-induced analgesia: electrical stimulation of dorsal column and dorsal roots attenuates dorsal horn neuronal excitability in neuropathic rats.
BACKGROUND
The sites of action and cellular mechanisms by which spinal cord stimulation reduces neuropathic pain remain unclear.


METHODS
We examined the effect of bipolar electrical-conditioning stimulation (50 Hz, 0.2 ms, 5 min) of the dorsal column and lumbar dorsal roots on the response properties of spinal wide dynamic range (WDR) neurons in rats after L5 spinal nerve injury. The conditioning stimulation intensity was set at the lowest current that evoked a peak antidromic sciatic Aα/β-compound action potential without inducing an Aδ- or C-compound action potential.


RESULTS
Within 15 min of the dorsal column or root conditioning stimulation, the spontaneous activity rate of WDR neurons was significantly reduced in nerve-injured rats. Conditioning stimulation also significantly attenuated WDR neuronal responses to mechanical stimuli in nerve-injured rats and inhibited the C-component of the neuronal response to graded intracutaneous electrical stimuli applied to the receptive field in nerve-injured and sham-operated rats. It is noteworthy that dorsal column stimulation blocked windup of WDR neuronal response to repetitive intracutaneous electrical stimulation (0.5 Hz) in nerve-injured and sham-operated rats, whereas dorsal root stimulation inhibited windup only in sham-operated rats. Therefore, stimulation of putative spinal substrates at A-fiber intensities with parameters similar to those used by patients with spinal cord stimulators attenuated established WDR neuronal hyperexcitability in the neuropathic condition and counteracted activity-dependent increase in neuronal excitability (i.e., windup).


CONCLUSIONS
These results suggest a potential cellular mechanism underlying spinal cord stimulation-induced pain relief. This in vivo model allows the neurophysiologic basis for spinal cord stimulation-induced analgesia to be studied.
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA. yguan1@jhmi.edu
Yun
Y
Guan
Paul W
PW
Wacnik
Fei
F
Yang
Alene F
AF
Carteret
Chih-Yang
CY
Chung
Richard A
RA
Meyer
Srinivasa N
SN
Raja
D000200:Action Potentials / Q000502:physiology; D000698:Analgesia; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D004599:Electric Stimulation Therapy / Q000379:methods*; D007839:Functional Laterality / Q000502:physiology; D008297:Male; D009437:Neuralgia / Q000523:psychology / Q000628:therapy*; D020671:Posterior Horn Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial; D012584:Sciatic Nerve / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000502:physiology*; D013127:Spinal Nerves / Q000293:injuries; D014140:Tracheotomy