In vitro selectivity of lisuride and other ergot derivatives for alpha 1- and alpha 2-adrenoceptors.

The alpha-adrenoceptor agonist and antagonist actions of lisuride and other ergot derivatives were assessed in spleen strips (alpha 1-adrenoceptor) and transmurally stimulated ileal preparations (alpha 2-adrenoceptor) from the guinea-pig. The compounds tested were devoid of alpha-adrenoceptor agonistic activity, however many were selective alpha-adrenoceptor antagonists. Lisuride was alpha 2-selective, having a pA2 value of 9.70 in guinea-pig ileal and 7.47 in splenic preparations. Conversely, bromocriptine was alpha 1-selective with a pA2 of 7.46 in spleen strips; it had no measurable effect in the ileum.