Oxytocic activity of two dihydrogenated ergot peptide alkaloids on the rabbit uterus in situ.

The effect of two recently synthetized dihydrogenated ergot peptide alkaloids has been investigated on the rabbit uterus in situ. The method is described in detail. 6-Nor-6-isopropyl-9,10-dihydro-2'beta-methyl-5'alpha-benzyl-ergopeptine (DZ 26-474) and 6-nor-6-idopropyl-9,10-dihydro2'8-methyl-5'alpha-isopropyl-ergopeptine (28-377) possess 33% and 59%, respectively, of the oxytocic activity of methylergometrine (Methergine). The uterotonic effect of DZ 26-474 and 28-377 can be completely abolished by pretreatment with alpha-adrenoceptor blocking drugs, indicating involvement of alpha-adrenoceptors. Results obtained are discussed in relation to the concept that dihydrogenated ergot peptide alkaloids usually inhibit spontaneous contractions of the uterus and contractions induced by methylergometrine.