Fig. 6. Isometric forces of femoral artery vascular rings obtained from MHS (black columns, n = 15 rings) and normal swine (white columns, n = 32 rings). At baseline, no significant differences in forces were detected between the groups. The addition of 0.2 μm phenylephrine (PHE) increased force development significantly in all preparations. The addition of succinylcholine 0.06 mm, the equivalent dose to 2 mg/kg intravenously, did not lead to a significant relaxation in rings from either group. Finally, 0.1 μm acetylcholine increased relaxation in both groups but more significantly in preparations from normal animals.