Regional study of spinal alpha 2-adrenoceptor densities after intraspinal noradrenergic-rich implants on adult rats bearing complete spinal cord transection or selective chemical noradrenergic denervation.

One of the challenges of restorative neuronal transplantation in the CNS of mammals is the appropriate integration of grafted cells in the host circuitry. One key parameter is the specific influence of grafted cells upon corresponding receptors. In order to test this issue on the lesioned spinal cord of adult rats, two models of spinal cord denervation were used: the first one consisted of a complete transection 1 week prior to an intraspinal transplantation of embryonic locus coeruleus (LC) primordia cell suspension; the second one was a chemical destruction of the spinal noradrenergic (NA) system 1 month prior to a similar transplantation. Five weeks after transplantation, spinal sections were processed for autoradiographic quantification of alpha 2-adrenoceptor binding sites densities. In most regions, alpha 2-adrenoceptor densities remained comparable or higher than before graft; interestingly, in lumbar dorsal horn, lumbar intermediate zone and sacral distal dorsal horn of transected-grafted rats, they returned to control level. Results are discussed in relation to the parallel study performed concerning alpha 1-adrenoceptors.