INTRASPINAL NORADRENERGIC-RICH IMPLANTS REVERSE THE INCREASE OF ALPHA(1) ADRENOCEPTORS DENSITIES CAUSED BY COMPLETE SPINAL-CORD TRANSECTIONOR SELECTIVE CHEMICAL DENERVATION - A QUANTITATIVE AUTORADIOGRAPHIC STUDY

This study examined, in the adult rat, whether the intraspinal transpl antation of a cell suspension of embryonic day (ED)13 rat locus coerul eus primordia was able to normalize the lesion-induced increase of spi nal alpha(1)-adrenoceptors. Two experimental models of spinal denervat ion were studied. The first model consisted of a complete spinal cord transection (thoracic vertebrae level T8-T9) and 1 week later, the cel l suspension was transplanted below the section; the second one was ob tained by a selective chemical lesion of the noradrenergic (NA) system and one month later, the cell suspension was implanted at the same le vel as in transected rats. Five weeks after grafting, all animals were sacrificed and spinal cord tissue sections were processed for immunoh istochemical detection of noradrenaline or for quantification of alpha (1)-adrenoceptors binding sites densities using [H-3]prazosin as a lig and. After 6-OHDA lesion, as well as caudally to the transection, a si gnificant increase by 21% (P < 0.01) to 68% (P < 0.001) of alpha(1)-ad renoceptors densities was detected. The implantation of embryonic NA n eurons into the denervated spinal cord led to a reversal of the lesion -induced increase of spinal alpha(1)-adrenoceptors, five weeks later. Moreover, this reversal seems to be more effective after mechanical th an after chemical denervation.