Fig. 3.

RT-PCR analysis of connexins expressed by normal adult and axotomized motor neurons. Using primers for each of the 13 known rodent connexins, PCR analysis was performed on cDNA from rat positive control tissues, such as heart (for Cx37, Cx40, Cx43, and Cx45), liver (for Cx26 and Cx32), eye (for Cx36, Cx46, and Cx50), skin (for Cx31.1, Cx30.3, and Cx31), and testis (for Cx33), normal spinal cord and spinal cord ipsilateral and contralateral to sciatic nerve cut 2 weeks previously. Corresponding RNAs were used as a negative controls. In each case, PCR products were eluted from gels, cloned, and sequenced to verify their identity. RNA was not pooled across animals, and the results shown here from one animal are representative of the other animals evaluated. A, B, Primers specific for Cx26, Cx32, and Cx36 amplified 364, 385, and 979 bp bands, respectively, from normal spinal cord, spinal cord contralateral and ipsilateral to sciatic nerve cut, and positive control tissue cDNA (Condorelli et al., 1998). Primers specific for Cx37, Cx40 (Haefliger et al., 1992), Cx43 (Beyer et al., 1987), and Cx45 (Schwarz et al., 1992) amplified 422, 308, 292, and 1217 bp bands, respectively, from normal spinal cord and spinal cord contralateral and ipsilateral to sciatic nerve cut and positive control tissue cDNA. Although Cx32 and Cx26 are detected by RT-PCR from spinal cord cDNA (B), in situ hybridization showed that these are not expressed by motor neurons (see Fig. 4).C, In contrast, primers against the other known rodent connexins amplified the predicted size band from positive control tissue but failed to amplify the same sized band in spinal cord. These results suggest that the repertoire of connexins expressed in lumbar spinal cord is unchanged after axotomy.