Long-term inhibition of ovulation by a GnRH-antagonist at low dose level

Ac-D-Trp1,3, D-Cpa2, D-Lys6, D-Ala10-GnRH has been prepared by solid phase synthesis. The peptide was found to completely inhibit ovulation when administered on proestrus day in a dose of 1.5 microgram/rat, s.c. The peptide completely inhibited ovulation for a period corresponding to three to four cycles when administered daily in a dose of 5 micrograms/rat, s.c. and caused 70% inhibition of ovulation in a dose of 3 micrograms/rat.