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.
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