Dorsal root ganglion (DRG) cells can be a source of abnormal neuronal activity transmitted to the spinal cord after nerve injury. We will use whole-cell patch-clamp recordings to study differences in the membrane properties of dissociated DRG cells from adult rats that are normal or that have had a nerve injury consisting of a tight or a loose ligation. We will study the effects of nerve ligation on (1) the distribution and proportion of the macroscopic tetrodotoxin (TTX) sensitive and/or TTX resistant sodium currents to test whether """"""""ligated cells"""""""" have a decrease in TTX resistant Na-currents, and (2) the proton and capsaicin evoked currents, in relation to TTX sensitivity, to test whether there is a more pronounced proton activated inward current, and whether protons are less effective in reducing the peak amplitude of the TTX-sensitive current in, ligated cells and (3) the norepinephrine-gated current to determine whether the norepinephrine evoked membrane depolarization is more pronounced in ligated cells and to determine whether alpha 1 or 2 receptors mediate the norepinephrine response. The results obtained are expected to provide new information on the origins of abnormal electrophysiological activity, in traumatized DRG cells, that might contribute to pain, dysesthesias and, in general, long term changes in the functional properties of certain spinal cord neurons.
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