To explore the vascular reactivity of abdominal aorta to agonists of alpha-adrenergic receptors in rat with high level transection of the spinal cord, and to quantify the expression of alpha-AR mRNA subtypes, in order to investigate relationship between alpha-AR and hyperreactivity of abdominal aorta.Four weeks after transection of the spinal cord at the level of 4th thoracic vertebra, the rats were sacrificed, and abdominal aorta rings were adopted to assay sensitivity to phenylephrine and clonidine with isolated organ perfusion system. Alpha(1A)-AR, alpha(1B)-AR, alpha(1D)-AR, alpha(2A)-AR, alpha(2B)-AR, alpha(2C)-AR mRNA expressions were quantified by real time polymerase chain reaction (PCR).Compared with abdominal aorta, of rat with sham operation, reactivity of aorta of rat after transection of spinal cord to clonidine was significantly higher (P0.05). Expressions of alpha(1A)-AR mRNA, alpha(1D)-AR mRNA, alpha(2A)-AR mRNA, alpha(2B)-AR mRNA, alpha(2C)-AR mRNA were significantly higher (P<0.05 or P<0.01), while the expression of alpha(1B)-AR mRNA did not vary significantly.Vascular hyperreactivity to agonist of alpha(2)-AR may be the mechanism of hyperreactivity of abdominal aorta in rat after transection of spinal cord. Although alpha(1)-AR mRNA expression is higher in aorta of rat with spinal cord injury, vascular hyperreactivity is not the result of upregulation of alpha(1)-AR sensitivity.