n-methylnaloxone and norbinaltorphimine

In this study, we aimed to study the effects of ICI204,448, naloxone methiodide and levocetirizine on the scratching behavior induced by intradermal injection of a ?-opioid antagonist, nor-binaltorphimine (nor-BNI), into the rostral back of ICR mice were investigated.. Male ICR mice weighing 30?35 g were used. The number of scratching episodes were counted for 60 min after i.d. injection of nor-BNI.. nor-BNI dose dependently increased in the number of scratching episodes in ICR mice. nor-BNI-induced scratching behavior was inhibited by not only nalfurafine but also ICI204,448, a peripherally selective ?-opioid agonist. Naloxone and naloxone methiodide, a peripherally restricted ?-opioid antagonist, also inhibited nor-BNI-induced scratching behavior. Scratching behavior induced by nor-BNI was inhibited by chlorpheniramine as well as levocetirizine, a third-generation H. These results suggest that scratching behavior induced by this ?-opioid antagonist, nor-BNI, is related to not only central but also peripheral opioid and H

Topics: Animals; Behavior, Animal; Cetirizine; Male; Mice; Mice, Inbred ICR; Naloxone; Naltrexone; Narcotic Antagonists; Pyrrolidines; Quaternary Ammonium Compounds

It was found that pretreatment of rats with selective agonist of kappa1-opioid receptors (OR) (-)--U--50.488 decreased the incidence of ischemic (10 min) and reperfusion (10 min) ventricular arrhythmias. The selective kappa2-OR agonist GR-89696 had no effect on the incidence of ventricular arrhythmias during a 10-min coronary artery occlusion and following reperfusion in anesthetized rats. The effect of (-)--U-50.488 was abolished by the selective kappa1-OR antagonist of non-binaltorphimine and the non-selective peripheral OR antagonist naloxone methiodide. Perfusion of isolated rat heart with (-)--U-50.488 did not affect arrhythmias during ischemia and reperfusion. The authors suggest that stimulation of kappa1-opioid receptors located outside the central nervous system increases heart resistance against arrhythmogenic action of ischemia/reperfusion, antiarrhythmic action of (-)--U-50.488 being mediated through extracardiac opioid receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Myocardial Reperfusion Injury; Myocardium; Naloxone; Naltrexone; Piperazines; Pyrrolidines; Quaternary Ammonium Compounds; Rats; Rats, Wistar; Receptors, Opioid, kappa

The aim of our study was to investigate the effect of intracerebroventricular (i.c.v.) administration of very low doses of opioid antagonists on the pain threshold, arterial blood pressure and body temperature of spontaneously hypertensive rats (SHR) with chronic pain. We found that low doses of i.c.v. administered naloxone hydrochloride (0.3 microg) or naloxone methiodide (0.4 microg) produce paradoxical hypoalgesia. Similar results were not observed following i.c.v. administration of nor-binaltorphimine (0.6 microg). A paradoxical increase in the severity of hypertension followed i.c.v. opioid antagonist administration. This suggests an involvement of the opioid system in the mechanisms of blood pressure control. The paradoxical results obtained both for pain threshold and blood pressure after low doses of some opioid antagonists seem to confirm the role played by opioid autoreceptors in these effects. Existence of autoreceptors is suggested. Results obtained following i.c.v. administration of nor-binaltorphimine also suggest a role for the kappa autoreceptor (OP2) in the regulatory mechanisms of thermoregulation.

Topics: Analgesia; Animals; Arteries; Blood Pressure; Body Temperature; Body Weight; Brain; Chronic Disease; Hypertension; Injections, Intraventricular; Male; Naloxone; Naltrexone; Narcotic Antagonists; Pain; Pain Threshold; Quaternary Ammonium Compounds; Rats; Rats, Inbred SHR; Rats, Inbred WKY