EVIDENCE THAT ERGOVALINE ACTS ON SEROTONIN RECEPTORS

Ergovaline is a potent vasoconstrictor of isolated bovine uterine and umbilical arteries. Contractions to ergovaline were slow to develop an d required 120 min or more to reach their maximum effect. Tissues cont racted to ergovaline did not relax over a 3 hr period despite repeated changing of the bath fluid with fresh Krebs solution. This indicates a high affinity of ergovaline for its tissue receptor. Contractions to ergovaline were antagonized by ketanserin and phenoxybenzamine but no t by prazosin or phentolamine. This indicates that 5-HT2 receptors but not adrenergic receptors are involved in the vasoconstriction. The re sults suggest that drugs effective in blocking 5-HT2 receptors may be useful in preventing or reducing the toxic symptoms due to ergovaline in animals consuming Acremonium coenophialum infected tall fescue.