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Figure 3 Effect of alpha-receptor blockade on the flow-mediated dilation (FMD)/nitroglycerin (NTG) response with and without lower body negative pressure (LBNP). (A) During phentolamine (PE) (solid squares), the LBNP-induced impairment in FMD (solid circles) could no longer be demonstrated (two-way repeated measures analysis of variance: *p = 0.046 control vs. PE). (B) Phentolamine (solid squares) did not change the NTG response compared with baseline (solid circles) (p = NS).