Effect of STZ-induced diabetes on responses to vasoconstrictor agonists. Concentration response curves for vasoconstriction evoked by phenylephrine (A), serotonin (B) and PGF2α (C) in conduit (upper panels) and resistance (lower panels) arteries. Responses were measured as a percentage of the constriction induced by 50 mM KCl and are shown for STZ-treated, diabetic (solid circles) and age-matched control rats. Data plotted are mean ± s.e.m. with n = 12–13 (phenylephrine), n = 12 (serotonin) or n = 3–10 (PGF2α). *P < 0.05, ***P < 0.001 versus control.