title: Systemic analgesic activity and delta-opioid selectivity in [2,6-dimethyl-Tyr1,D-Pen2,D-Pen5]enkephalin.
abstract: The cyclic peptide [2,6-dimethyl-Tyr1,D-Pen2,D-Pen5]enkephalin (2) was synthesized by solid-phase techniques and contains the optically pure unnatural amino acid 2,6-dimethyltyrosine (DMT) as a replacement for the Tyr1 residue of [D-Pen2,D-Pen5]enkephalin (DPDPE, 1). This structural modification resulted in a 10-fold increase in the potency of 2 at the delta opioid receptor and a 35-fold increase in potency at the mu receptor while substantial delta receptor selectivity was maintained. In addition, 2 was 86-fold more effective than 1 at inhibiting electrically stimulated contractions of the mouse vas deferens. In the hot plate test, 2 was 7-fold more potent than 1 after intracerebroventricular administration in the mouse. While 1 was inactive following systemic administration of doses as high as 30 mg/kg, subcutaneous administration of 2 significantly inhibited writhing with an ED50 of 2.6 mg/kg. These results demonstrate that the potency and systemic activity of DPDPE are significantly increased by replacement of Tyr1 with DMT.
authors.affiliation: Searle Research and Development, CNS Diseases Research Department, G.D. Searle & Co., Skokie, Illinois 60077.
authors.forename: D W
authors.initials: DW
authors.lastname: Hansen
authors.forename: A
authors.initials: A
authors.lastname: Stapelfeld
authors.forename: M A
authors.initials: MA
authors.lastname: Savage
authors.forename: M
authors.initials: M
authors.lastname: Reichman
authors.forename: D L
authors.initials: DL
authors.lastname: Hammond
authors.forename: R C
authors.initials: RC
authors.lastname: Haaseth
authors.forename: H I
authors.initials: HI
authors.lastname: Mosberg
mesh_terms: D000698:Analgesia; D000700:Analgesics / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004558:Electric Stimulation; D004745:Enkephalins / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009119:Muscle Contraction / Q000187:drug effects; D010147:Pain Measurement; D011957:Receptors, Opioid / Q000502:physiology*; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D013329:Structure-Activity Relationship; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology
chemical_list: D000700:Analgesics; D004745:Enkephalins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; C073188:enkephalin, 2,6-dimethyl-Tyr(1)-Pen(2,5)-