Figure 3. The effects of (A) 10 sup -6 M prazosin, a selective alpha1-antagonist (diameter 262+/-14 micro meter, n = 6 middle cerebral arteries); (B) 10 sup -6 M phentolamine, a nonselective alpha-antagonist (diameter 251+/-13 micro meter, n = 8 middle cerebral arteries); (C) 10 sup -6 M idazoxan, a selective alpha2-antagonist (241+/-7 micro meter, n = 7 middle cerebral arteries); and (D) 10 sup -5 M rauwolscine, a selective alpha2-antagonist (diameter 240+/-4 micro meter, n = 5 middle cerebral arteries), on the dilations of rat middle cerebral arteries produced by UK14,304 *P < 0.05 compared to control.