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Normal distribution of alpha 2‐adrenoceptors in the rat spinal cord and its modification after noradrenergic denervation: A quantitative autoradiographic study

1994; Wiley; Volume: 39; Issue: 3 Linguagem: Inglês

10.1002/jnr.490390309

1097-4547

C. Roudet, Patrick Mouchet, Claude Feuerstein, Marc Savasta,

Neuroscience and Neuropharmacology Research

Abstract The distribution of alpha 2 (α 2 )‐adrenoceptors along cervical, thoracic, lumbar, and sacral segments of the spinal cord of normal rats has been studied by quantitative autoradiography using the specific α 2 ‐antagonist [ 3 H]rauwolscine as a ligand. In addition, the influence of noradrenergic (NA) denervation [obtained either by complete transection of the spinal cord at vertebrae level T8–T9 or by selective lesion of NA spinal cord system carried out by intracisternal injection of 6‐hydroxydopamine (6‐OHDA)] on eventual variations of α 2 ‐adrenoceptor density at spinal cord target cells was studied in parallel. In control rats, the quantitative analysis of α 2 ‐adrenoceptor densities revealed the presence of these receptors throughout the whole gray matter with a preferential location in the superficial dorsal horn. This pattern was the same at all rostro‐caudal levels of the cord and appeared very well correlated with the distribution of NA terminals revealed by immunohistochemistry, particularly in the supeficial layers of the dorsal horn. After total transection of the spinal cord (caudally to the section) and 6‐OHDA‐induced lesion, an increase of α 2 ‐adrenoceptor density was mainly observed within the distal dorsal horn thus evidencing supersensitivity in this area, while modifications were not detectable in other regions of the spinal gray matter, except at the lumbar level where other dorsal, central, and intermediate zones were significantly enriched. © 1994 Wiley‐Liss, Inc.