title: [D-Ala2]-methionine enkephalinamide reflexively induces antinociception by activating vagal afferents.
abstract: Experiment 1 showed that intravenous administration of [D-Ala2]-methionine enkephalinamide resulted in dose-dependent inhibition of the tail-flick reflex, mild hypotension, and bradycardia. The enkephalinamide-induced inhibition of the tail-flick reflex and cardiovascular effects were eliminated in the bilateral cervical vagotomized anesthetized rat preparation, but were unaffected by either a unilateral right vagotomy or bilateral sinoaortic deafferentation in the conscious rat preparation. Experiment 2 demonstrated that the antinociceptive and cardiovascular actions of enkephalinamide were eliminated by pretreatment with intravenous administration of the opioid-receptor antagonist naloxone. These experiments strongly suggest that peripherally circulating enkephalins could reflexively induce analgesia by activating cardiopulmonary receptors whose afferents travel in the vagi.
mesh_terms: D000344:Afferent Pathways / Q000187:drug effects; D000698:Analgesia; D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000187:drug effects*; D014630:Vagus Nerve / Q000187:drug effects* / Q000502:physiology
chemical_list: D004744:Enkephalin, Methionine; C022118:enkephalinamide-Met, Ala(2)-