Expression and transport of Angiotensin II AT 1 receptors in spinal cord, dorsal root ganglia and sciatic nerve of the rat

Abstract

To clarify the role of Angiotensin II in the regulation of peripheral sensory and motor systems, we initiated a study of the expression, localization and transport of Angiotensin II receptor types in the rat sciatic nerve pathway, including L 4–L 5 spinal cord segments, the corresponding dorsal root ganglia (DRGs) and the sciatic nerve. We used quantitative autoradiography for AT 1 and AT 2 receptors, and in situ hybridization to detect AT 1A, AT 1B and AT 2 mRNAs. We found substantial expression and discrete localization of Angiotensin II AT 1 receptors, with much higher numbers in the grey than in the white matter. A very high AT 1 receptor expression was detected in the superficial dorsal horns and in neuronal clusters of the DRGs. Expression of AT 1A mRNA was significantly higher than that of AT 1B. AT 1 receptor binding and AT 1A and AT 1B mRNAs were especially prominent in ventral horn motor neurons, and in the DRG neuronal cells. Unilateral dorsal rhizotomy significantly reduced AT 1 receptor binding in the ipsilateral side of the superficial dorsal horn, indicating that a substantial number of dorsal horn AT 1 receptors have their origin in the DRGs. After ligation of the sciatic nerve, there was a high accumulation of AT 1 receptors proximal to the ligature, a demonstration of anterograde receptor transport. We found inconsistent levels of AT 2 receptor binding and mRNA. Our results suggest multiple roles of Angiotensin II AT 1 receptors in the regulation of sensory and motor functions.