Association of serotonin and ergot alkaloids on tissue partitioning and contractile response of bovine blood vessels

Ergot alkaloids can bind serotonin (5-HT) receptors interfering with many physiological functions. However, the mechanism has not been completely established. The objective was to evaluate whether the association of 5-HT and the ergot alkaloid, ergovaline, in a 24-h pre-incubation can affect vascular tissue partitioning and contractile responses. Cross-sections of saphenous veins from five steers were used. In the tissue partitioning experiment, the treatments were the combination of three levels of ergovaline (2.01 × 10⁻⁸ M, 2.01 × 10⁻⁷ M and 2.01 × 10⁻⁶ M) with three levels of 5-HT and a control (5 × 10⁻⁸ M, 5 × 10⁻⁷ M, 5 × 10⁻⁶ M and 0 M). After 24-h exposure to the treatments, the blood vessels were washed. Afterward, the tissues were analyzed for ergovaline and 5-HT concentrations. For the contractility experiment, a parallel set of blood vessels was evaluated in the myograph after 24-h pre-incubation with the respective treatments: 1) no additional compound; 2) tall fescue seed extract (2.01 × 10⁻⁷ M of ergovaline); 3) serotonin (5 × 10⁻⁷ M); or 4) ERV plus 5-HT. The tissue ergovaline increased (P < 0.001) about 27.5-fold when the concentration in the media increased 100-fold (2.01 × 10⁻⁸ M to 2.01 × 10⁻⁶ M). However, the presence of 5-HT did not affect (P = 0.368) tissue ergovaline partitioning. When 5-HT was not added, ergovaline reduced (P < 0.05) the 5-HT concentration in the blood vessel. Pre-incubation with ergovaline reduced contractile response by about 95 % (P < 0.05) and 5-HT did not change its effect. Ergot alkaloid partitioning is associated with reduced tissue 5-HT levels and blood vessel contractility.