title: Pharmacological characterization of EN-9, a novel chimeric peptide of endomorphin-2 and neuropeptide FF that produces potent antinociceptive activity and limited tolerance.
abstract: Mounting evidences indicate the functional interactions between neuropeptide FF (NPFF) and opioids, including the endogenous opioids. In the present work, EN-9, a chimeric peptide containing the functional domains of the endogenous opioid endomorphin-2 (EM-2) and NPFF, was synthesized and pharmacologically characterized. In vitro cAMP assay demonstrated that EN-9 was a multifunctional agonist of κ-opioid, NPFF1 and NPFF2 receptors. In the mouse tail-flick test, intracerebroventricularly (i.c.v.) administration of EN-9 produced significant antinociception with an ED50 value of 13.44 nmol, which lasted longer than that of EM-2. In addition, EN-9 induced potent antinociception after both intravenous (i.v.) and subcutaneous (s.c.) injection. Furthermore, the experiments using the antagonists of opioid and NPFF receptors indicated that the central antinociception of EN-9 was mainly mediated by κ-opioid receptor, independently on NPFF receptors. Notably, the central antinociception of EN-9 was not reduced over a period of 6 days repeated i.c.v. injection. Repeated i.c.v. administration of EN-9 with the NPFF1 and NPFF2 receptors antagonist RF9 resulted in a progressive loss of analgesic potency, consistent with the development of tolerance. Moreover, central administration of EN-9 induced the place conditioning aversion only at a high dose of 60 nmol, but not at low doses. At supraspinal level, only high dose of EN-9 (60 nmol, i.c.v.) inhibited gastrointestinal transit via NPFF receptors. Similarly, systemic administration of EN-9 also inhibited gastrointestinal transit at high doses (10 and 30 mg/kg, i.v.). Taken together, the multifunctional agonist of κ-opioid and NPFF receptors EN-9 produced a potent, non-tolerance forming antinociception with limited side effects.
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Zi-Long
authors.initials: ZL
authors.lastname: Wang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Pei
authors.initials: P
authors.lastname: Wang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Hong-Hai
authors.initials: HH
authors.lastname: Tang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Zheng-Lan
authors.initials: ZL
authors.lastname: Han
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Jing-Jing
authors.initials: JJ
authors.lastname: Song
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Xu-Hui
authors.initials: XH
authors.lastname: Li
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Hong-Ping
authors.initials: HP
authors.lastname: Yu
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Run
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Biao
authors.initials: B
authors.lastname: Xu
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China.
authors.forename: Meng-Na
authors.initials: MN
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China. Electronic address: fangq@lzu.edu.cn.
authors.forename: Quan
authors.initials: Q
authors.lastname: Fang
authors.affiliation: Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, 199 Donggang West Road, Lanzhou, 730000, PR China. Electronic address: wangrui@lzu.edu.cn.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
mesh_terms: D000700:Analgesics / Q000008:administration & dosage / Q000737:chemistry; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000737:chemistry; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D009842:Oligopeptides / Q000008:administration & dosage* / Q000737:chemistry; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D010446:Peptide Fragments / Q000008:administration & dosage* / Q000737:chemistry; D010455:Peptides / Q000008:administration & dosage* / Q000737:chemistry; D018013:Receptors, Neuropeptide / Q000819:agonists / Q000502:physiology; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000502:physiology
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; C000621225:EN-9 chimeric peptide; D009842:Oligopeptides; D010446:Peptide Fragments; D010455:Peptides; D018013:Receptors, Neuropeptide; D017473:Receptors, Opioid, kappa; C083929:neuropeptide FF receptor; C105294:endomorphin 2; C053651:phenylalanyl-leucyl-phenylalanyl-glutaminyl-prolyl-glutaminyl-arginyl-phenylalaninamide
keywords: Antinociception; Chimeric peptide; Endomorphin-2; IBMX (PubChem CID: 3758); NPFF (PubChem CID: 123797); Neuropeptide FF; Non-tolerance; Opioid; RF9 (PubChem CID: 53320361); beta-Funaltrexamine (PubChem CID: 5311018); endomorphin-2 (PubChem CID: 5311081); forskolin (PubChem CID: 47936); morphine (PubChem CID: 5288826); naloxone (PubChem CID: 5464092); naltrindole (PubChem CID: 5497186); nor-binaltorphimine (PubChem CID: 5480230)