The antitussive effects of endomorphin-1 and endomorphin-2 in mice

• Published in: European journal of pharmacology Vol. 467; no. 1; pp. 219 - 222
• Main Authors: Kamei, Junzo, Morita, Kayo, Saitoh, Akiyoshi, Nagase, Hiroshi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 25.04.2003; Elsevier
• Subjects: Animals; Antitussive Agents - pharmacology; Antitussive effect; Biological and medical sciences; Capsaicin; Cough - chemically induced; Cough - drug therapy; Cough reflex; Dose-Response Relationship, Drug; Endomorphin-1; Endomorphin-2; Injections, Intraventricular; Male; Medical sciences; Mice; Mice, Inbred ICR; Naloxone - analogs & derivatives; Naloxone - pharmacology; Naltrexone - analogs & derivatives; Naltrexone - pharmacology; Oligopeptides - administration & dosage; Oligopeptides - pharmacology; Oligopeptides - physiology; Receptors, Opioid, kappa - antagonists & inhibitors; Receptors, Opioid, kappa - physiology; Receptors, Opioid, mu - agonists; Receptors, Opioid, mu - antagonists & inhibitors; Receptors, Opioid, mu - physiology; κ-Opioid receptor; μ-Opioid receptor; μ-Opioid receptor; Cough reflex; κ-Opioid receptor; Endomorphin-1; Antitussive effect; Endomorphin-2; K-Opioid receptor
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/S0014-2999(03)01634-0

The antitussive effects of endomorphin-1 and endomorphin-2, endogenous μ-opioid receptor agonists, on capsaicin-induced coughs were examined in mice. Endomorphin-2, at doses of 3, 10 and 30 μg, i.c.v., dose-dependently inhibited the number of capsaicin-induced coughs. However, the same doses (3, 10 and 30 μg) of endomorphin-1 injected with i.c.v. had no significant effects on the number of capsaicin-induced coughs. The antitussive effect of endomorphin-2 was significantly reduced by β-funaltrexamine, a μ 1/μ 2-opioid receptor antagonist, but not naloxonazine, a selective μ 1-opioid receptor antagonist. Furthermore, the antitussive effect of endomorphin-2 was also partially but significantly reduced by nor-binaltorphimine, a selective κ-opioid receptor antagonist. These results indicate that the administration of the endogenous μ-opioid ligand endomorphin-2, but not endomorphin-1, into the brain produces an antitussive effect via mainly naloxonazine-insensitive μ-opioid receptors, namely μ 2-opioid receptors and partially κ-opioid receptors.