, 1997). The resulting reorganization has been reported

using electrophysiological mapping of receptive fields (Rhoades et al., 1993), transganglionic labeling (Maslany et al., 1990 and Maslany et al., 1991), receptor expression mapping (Foschini et al., 1994), and metabolic uptake measurement (Crockett et al., 1993). There is also evidence that CN reorganization plays some role in cortical reorganization (Bowlus et al., 2003, Killackey and Dawson, 1989, Lane et al., 1995 and Lane et al., 2008). The forepaw barrel subfield (FBS) in primary somatosensory cortex in rat contains CO-stained clusters (called GDC-0068 solubility dmso barrels) that are associated with the representation of the glabrous forepaw digits, digit pads, and palmar pads (Waters et al., 1995); this cluster arrangement of CO labeling in rat SI is similar to that reported in rat CN (Li et al., 2012). The representation of the wrist lies within a nebulously stained field immediately posterior to the FBS and is bordered successively by the representations of the forearm, upper arm, and shoulder, hereby described as the “original shoulder”. Following forelimb amputation in juvenile rats, new input from the shoulder moves in to occupy the deafferented cortical space left vacant in the FBS (Pearson et al., 1999). The new input first appears 4 weeks after

amputation, and by 6 weeks post-amputation, the shoulder representation occupies large regions of the FBS (Pearson et al., 2003). The new

shoulder representation Androgen Receptor Antagonist chemical structure does not derive from the original shoulder representation or from Elongation factor 2 kinase the shoulder representation in second somatosensory cortex (SII) (Pearson et al., 2001). This finding led us to speculate that subcortical loci in the ventral posterior lateral thalamus (VPL) and/or cuneate nucleus (CN) are likely responsible for the expression of delayed large-scale cortical reorganization in the FBS. In the present study, we used extracellular recording techniques in rat to examine the input to CN during the first 12 weeks following forelimb amputation and at 26 and 30 weeks post-amputation in order to compare the temporal pattern of reorganization with that previously reported in the FBS (Pearson et al., 2003). We hypothesized that CN would display a pattern of reorganization similar to that previously reported in the FBS, but the time of first appearance of the new input from the shoulder in CN would occur prior to or simultaneously with its expression in the cortex. Our data show that CN reorganization begins within one week after amputation. New input from the body/chest and/or head/neck appears in the medial and lateral zones. In contrast, significant new input from the shoulder and reorganization within the central zone are absent. These results run counter to our prediction that CN forms a substrate for delayed large-scale cortical reorganization. A total of 39 juvenile Sprague-Dawley rats was used in this study.