title: Alanine analogues of [D-Trp]CJ-15,208: novel opioid activity profiles and prevention of drug- and stress-induced reinstatement of cocaine-seeking behaviour.
abstract: OBJECTIVE
  The novel macrocyclic peptide cyclo[Phe-D-Pro-Phe-D-Trp] ([D-Trp]CJ-15,208) exhibits κ opioid (KOP) receptor antagonist activity in both in vitro and in vivo assays. The four alanine analogues of this peptide were synthesized and characterized both in vitro and in vivo to assess the contribution of different amino acid residues to the activity of [D-Trp]CJ-15,208.
  
  
  METHODS
  The peptides were synthesized by a combination of solid phase peptide synthesis and cyclization in solution. The analogues were evaluated in vitro in receptor binding and functional assays, and in vivo with mice using a tail-withdrawal assay for antinociceptive and opioid antagonist activity. Mice demonstrating extinction of cocaine conditioned-place preference (CPP) were pretreated with selected analogues to evaluate prevention of stress or cocaine-induced reinstatement of CPP.
  
  
  RESULTS
  The alanine analogues displayed pharmacological profiles in vivo distinctly different from [D-Trp]CJ-15,208. While the analogues exhibited varying opioid receptor affinities and κ and μ opioid receptor antagonist activity in vitro, they produced potent opioid receptor-mediated antinociception (ED50 = 0.28-4.19 nmol, i.c.v.) in vivo. Three of the analogues also displayed KOP receptor antagonist activity in vivo. Pretreatment with an analogue exhibiting both KOP receptor agonist and antagonist activity in vivo prevented both cocaine- and stress-induced reinstatement of cocaine-seeking behaviour in the CPP assay in a time-dependent manner.
  
  
  CONCLUSIONS
  These unusual macrocyclic peptides exhibit in vivo opioid activity profiles different from the parent compound and represent novel compounds for potential development as therapeutics for drug abuse and possibly as analgesics.
authors.affiliation: Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS, USA.
authors.forename: J V
authors.initials: JV
authors.lastname: Aldrich
authors.forename: S N
authors.initials: SN
authors.lastname: Senadheera
authors.forename: N C
authors.initials: NC
authors.lastname: Ross
authors.forename: K A
authors.initials: KA
authors.lastname: Reilley
authors.forename: M L
authors.initials: ML
authors.lastname: Ganno
authors.forename: S E
authors.initials: SE
authors.lastname: Eans
authors.forename: T F
authors.initials: TF
authors.lastname: Murray
authors.forename: J P
authors.initials: JP
authors.lastname: McLaughlin
mesh_terms: D000409:Alanine / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry; D000701:Analgesics, Opioid / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D016466:CHO Cells; D003042:Cocaine / Q000008:administration & dosage*; D003213:Conditioning, Psychological / Q000187:drug effects; D003412:Cricetulus; D058999:Drug-Seeking Behavior / Q000187:drug effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009292:Narcotic Antagonists / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000037:antagonists & inhibitors; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors; D013315:Stress, Psychological / Q000517:prevention & control; D013997:Time Factors
chemical_list: D000596:Amino Acids; D000701:Analgesics, Opioid; C540936:CJ 15,208; D009292:Narcotic Antagonists; D010456:Peptides, Cyclic; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D003042:Cocaine; D000409:Alanine
keywords: CJ-15,208; analgesic; cocaine reinstatement; macrocyclic peptide; κ opioid receptor antagonist