Endomorphin 1 and 2 have vasodepressor activity in the anesthetized mouse.
ABSTRACT The endogenous peptides endomorphin 1 and 2 are newly discovered, potent, selective mu-opioid receptor agonists. In the present study, we investigated responses to the endomorphin peptides in the systemic vascular bed of the anesthetized mouse. Endomorphin 1 and 2 induced dose-related decreases in mean arterial pressure when injected in doses of 3-100 nmol/kg i.v. Mean arterial pressure decreased 14 +/- 4, 23 +/- 4, and 42 +/- 5 mm Hg at the 10, 30, and 100 nmol/kg doses, respectively, of endomorphin 1 (n = 5-7; p < 0.05), and similar changes were observed in response to endomorphin 2. In terms of relative vasodepressor activity, endomorphin 1 and 2 were about equipotent and about threefold more potent than the mu-opioid selective agonist PL017 in decreasing mean arterial pressure; all three peptides decreased heart rate. The time-course of the vasodepressor responses to endomorphin 1 and 2 were similar in rate of onset and decay. Vasodepressor responses to endomorphin 1 and 2 and PL017 but not to nociceptin were inhibited by the opioid receptor antagonist naloxone in a dose of 2 mg/kg i.v. When compared in the mouse and rat, the relative decreases in systemic arterial pressure in response to i.v. injections of endomorphin 1 and 2 did not differ greatly. However, the duration of the vasodepressor response was significantly longer in the rat. These results demonstrate that endomorphin 1 and 2 have significant, naloxone-sensitive, vasodepressor activity in the mouse.
Article: Endogenous opiates: 1998.[show abstract] [hide abstract]
ABSTRACT: This paper is the twenty-first installment of our annual review of research concerning the opiate system. It summarizes papers published during 1998 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; eating and drinking; alcohol; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurologic disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunologic responses; and other behaviors.Peptides 01/2000; 20(12):1527-74. · 2.43 Impact Factor