Abstract: Two sets of hormonal peptides are synthesized which are super agonists of the lutenizing hormone releasing hormone (LHRH). Chronic administration results in the inhibition of LHRH which is responsible for stimulating cell growth in the testes. One peptide has the D(dextro)-form of a mono-heterocyclic amino acid in position six (D-3-pyridyl-alanine) while the other peptide has a bi-heterocyclic amino acid in that same position (.beta.-(3-quinolyl)-D-.alpha.-alanine. Both peptides are less metabolically reactive than those in the prior art and yet both peptides are significantly more potent than LHRH itself.

Abstract: Two sets of hormonal peptides are synthesized which are super agonists of the luteinizing hormone releasing hormone (LHRH). Chronic administration results in the inhibition of LHRH which is responsible for stimulating cell growth in the testes. One peptide has the D(dextro)-form of a monoheterocyclic amino acid in position six (D-3-pyridyl-alanine) while the other peptide has a bi-heterocyclic amino acid in that same position (.beta.-(3-quinolyl)-D-.alpha.-alanine. Both peptides are less metabolically reactive than those in the prior art and yet both peptides are significantly more potent than LHRH itself.

Abstract: Undecapeptides retaining the amino acids in positions 2, 3, 4, 5, 6, 8 and 10 of substance P (Arg.sup.1 -Pro.sup.2 -Lys.sup.3 -Pro.sup.4 -Gln.sup.5 -Gln.sup.6 -Phe.sup.7 -Phe.sup.8 -Gly.sup.9 -Leu.sup.10 -Met.sup.11 -NH.sub.2), but having substitutions in positions 1, 7, 9 and 11 of substance P have been discovered to have high antagonistic activity to block substance P in biological systems. Exemplifying these potent antagonists is D-Arg.sup.1,D-Trp.sup.7,D-Trp.sup.9 -Leu.sup.11 -Substance P, which is an effective inhibitor and has high potency. These antagonists of substance P are useful to elucidate some biological mechanisms of substance P, and to treat inflammatory responses in the eye for medical practice in ophthalmology, and to be novel analgesic agents for medical applications.