Figure 2. Changes in skin blood flow during the venoarteriolar (VA) response and during local administration of clonidine at the vehicle treated (open bars) and yohimbine treated (grey bars) sites.

Inhibition of α₂-adrenoceptors with yohimbine did not significantly affect the decrease in skin blood flow during the venoarteriolar response. The lack of change in skin blood flow at the yohimbine treated site during administration of the α₂-adrenoceptors agonist clonidine demonstrates the efficacy of the dose of yohimbine at blocking α₂-adrenoceptors. Numbers in parentheses show skin blood flow prior to arm dependency and local administration of clonidine.