Figure 2. Effects of prazosin, yohimbine, or propranolol on 10 sup -3 M ropivacaine-induced vasoconstriction or bupivacaine-induced vasodilation for spinal pial arterioles (n = 18 each) in 18 dogs. With pretreatment of these blockers, alteration of spinal pial arterioles after subsequent 10 sup -3 M ropivacaine or bupivacaine were not inhibited. Values are expressed as mean +/- SEM.