[Changes in systemic and local vascular reactivity in hemorrhagic shock and the therapeutic effect of delta opioid receptor antagonist ICI174,864].

OBJECTIVE

To investigate the changes in systemic and local vascular reactivity following hemorrhagic shock of different severity and the therapeutic effect of alpha opioid receptor antagonist ICI174,864.

METHODS

Fifty-six Wistar rats were used in two experiments. In experiment I, 32 rats were equally divided into sham operation group, 1 hour, 2 hours and 3 hours hypotension groups. In the latter groups, rats were bled to a mean arterial blood pressure (MAP) of 40 mm Hg (1 mm Hg=0.133 kPa) and maintained at this level for 1, 2, 3 hours, respectively. The pressor response of blood pressure and the contractile response of superior mesenteric artery (SMA) to norepinephrine(NE, 3 ug/kg) were observed after shed blood was reinfused. In experiment II, 24 rats were divided into shock control, ICI174,864 0.5 mg/kg and 1.0 mg/kg groups. The response of blood pressure and SMA contractility to NE (3 microg/kg) were observed at 1, 2, and 4 hours after ICI174,864 administration.

RESULTS

Following hemorrhagic shock, the systemic and local (SMA) vascular responsiveness was significantly decreased significantly and it was time dependent. Shed blood reinfusion alone did not restore the decreased vascular reactivity. ICI174,864 improved the decreased vascular reactivity in dose-dependent manner.

CONCLUSION

Hemorrhagic shock can induce systemic and local vascular hyporeactivity. The decreased vascular reactivity is closely associated with the severity and duration of shock. Loss of systemic vascular reactivity parallels to that of the regional vessel. delta opioid receptor antagonist ICI174,864 has some beneficial effect in improving vascular hyporeactivity.