Effect Of Naloxone And Anisodamine On Vascular Response To NE During The Period Of Vascular Hyposensitivity In HS Rabbit

OBJECTIVE The purpose of the study is to investigate whether naloxone (NAL)and anisodamine (654-2) effects at the vascular hyporesponsiveness to norepinephrine (NE) and the change of nitric oxide (NO) and superoxide dismutase (SOD) in hemorrhagic shock (HS). METHODS Part 1: Six rabbits were anesthetized with pentobarbital (25mg/kg) and subjected to withdrawing blood from the femoral artery. Maintain the mean arterial pressure (MAP) at 40-50mmHg for 3 hours. NE(5ug/kg)was injected interval 30 min. The vascular responsibility of constriction was measured by monitoring the changes of the MAP. Part 2: Eigtheen rabbits were divided in 3 groups: group A (n=6), served as control; group B (n=6), as naloxone treatmeat; group C (n=6), as anisodamine treatmeat. The modle of vascular hyposensitivity in HS rabbits was prepared by withdrawing blood from the femoral artery. Saline, NAL(1mg/kg), 654-2(2mg/kg) intravenous was given at 50 min after HS (before vascular hyposensitivity). NE(5ug/kg)was injected interval 30 min and monitor the changes of the MAP. At the same time, the activity of plasma NO and SOD were detected at 1 hour, 2 hour, 3 hour after HS . RESULTS The vascular reponse to NE was hyperresponsive at 30 min after HS and hyporesponsive after the long period of HS(longer than 1h).10min and 40min after treatment with NAL, the MAP was markedly increased compared with controls and 654-2 treatmeats (P<0.05). Meanwhile, plasma NO was declined compared with controls and 654-2 treatmeats(P<0.05), and it was closely related to the significant elevation of MAP. But no significant changes in plasma SOD activity(P>0.05). In addition, there was no significant difference in MAP, plasma NO and SOD level between control and 654-2 treatmeats(P>0.05). CONCLUSION NAL improve the vascular response to NE during the period of vascular hyposensitivity in HS rabbits and NO plays an important role in vascular hyposensitivity. 654-2 can't improve the vascular response to NE during the period of vascular hyposensitivity in HS rabbits.