INVESTIGATIONS ON THE MODE OF ACTION OF ERGOTAMINE IN THE ISOLATED FEMORAL VEIN OF THE DOG

Abstract

1 Experiments on spiral strips cut from the femoral vein of dogs suspended in Krebs-Henseleit solution were carried out. 2 Ergotamine caused stimulation in concentrations about 350 times lower than noradrenaline (ED₅₀ of ergotamine = 2.2 × 10⁻⁹ m; ED₅₀ of noradrenaline = 7.6 × 10⁻⁷ M), but the maximal responses to ergotamine were only about one third those to noradrenaline. 3 The pA₂ value of ergotamine against noradrenaline was 8.8. 4 The effects of ergotamine can be blocked by prior administration of phentolamine. The pA₂ value for phentolamine against ergotamine was 6.8 and the pA₂ value for phentolamine against noradrenaline was 7.5. 5 It is concluded that the stimulant action of ergotamine on smooth vascular muscle probably is mediated mainly via α-adrenoceptors.