The deafferented ipsilateral CN and adjacent brainstem, in the vicinity of the obex, were physiologically mapped between 1 and 12 weeks and at 26 weeks and 30 click here weeks post-amputation. In these forelimb amputee rats, 631 electrode penetrations were made and receptive fields were examined at 4675 sites. An additional 5 juvenile Sprague-Dawley rats that did not undergo forelimb amputation served as controls and were similarly mapped by making 58 penetrations and examining receptive fields at 829 sites. The total number of electrode penetrations and total number of recording sites examined for intact and forelimb amputees are shown in Table 1. A relationship exists between the physiological
and morphological organization of the glabrous forepaw representation in CN. In the
present study, we focused on the region approximately +300 μm anterior to the obex that contained CO-labeled clusters, called barrelettes, that were associated with the representation of the glabrous digits and digit and palmar pads (Li et al., 2012). While these CO-stained clusters are found throughout an 800-to900-μm rostrocaudal segment of CN, cross sections taken around +300 μm generally contained a complete complement of forepaw barrelettes AZD9291 nmr that could be directly compared to barrel-like structures in the forepaw barrel subfield (FBS) in SI cortex (Waters et al., 1995). Examples of 4 intact animals with well-defined barrelettes in CN lying approximately +300 μm anterior to the obex are illustrated in photomicrographs and corresponding line drawings in Fig. 1. The locations of the barrelettes within CN, the general shape of CN,
and the location of CN in relationship to the surrounding gracilis nucleus (GN) and spinal trigeminal nucleus (STN) are shown. In each example, the barrelettes are well formed and occupy the central region of CN. On the dorsomedial corner, beginning at the dashed line in the line drawings, CN extends toward and appears to abut or blend into the neighboring GN. The dorsolateral side of CN forms a tail-like most structure that can be seen extending toward the brainstem surface and the neighboring STN. These are common features of coronal sections at this level of CN. For each of the forelimb-intact control rats, a detailed physiological map of the forelimb and surrounding body representation(s) was generated by making rows of closely spaced electrode penetrations and sampling at depths of 50 or 100 μm throughout the penetration down to a depth of 700 μm. Penetrations were then reconstructed in relationship to the underlying morphological map to produce a standardized map for subsequent comparison with forelimb amputees. An example from one intact rat is illustrated in Fig. 2. The photomicrograph in Fig. 2A shows a view of the brainstem surface with the locations of the surface point of entry of 7 electrode penetrations used to generate the physiological map.