Figure 5.

Contractile response of lateral saphenous veins (expressed as percentage of the maximal response induced by 1 × 10⁻⁴ M norepinephrine) to increasing concentrations of TCB2, an 5-hydroxytryptamine_2A receptor agonist in: (a) Experiment 1 on Days 0, 7, 14, and 28 (−logEC₅₀ = 4.71, 4.92, 4.76, and 4.65, respectively) after steers were removed from a tall fescue pasture and placed on a non-toxic diet (day × TCB2 concentration interaction was not significant (p = 0.39)); and (b) Experiment 2 on Days 0, 21, 42, and 63 (−logEC₅₀ = 4.67, 4.64, 4.75, and 5.02, respectively) after steers were removed from a tall fescue pasture and placed on a non-toxic diet (day × TCB2 concentration interaction was significant (p < 0.01)). Comparison of contractile responses of lateral saphenous veins biopsied from steers that had grazed toxic tall fescue (red lines) and non-toxic bermudagrass (black lines) pastures at (c) 0 and (d) 63 days after removal from pasture in Experiment 2.