title: A characterization of kyotorphin (Tyr-Arg)-induced antinociception.
abstract: Intracerebroventricular administration of kyotorphin (Tyr-Arg) or Tyr-D-Arg to mice or intrathecal administration of kyotorphin to rats resulted in a dose-dependent, long-lasting, naloxone-reversible analgesia as measured by the 48 degrees C hot plate assay. The potency of kyotorphin was equal to that of Met-enkephalin although its duration of action was substantially longer. Cross-tolerance to kyotorphin could be demonstrated in animals made tolerant to morphine by chronic morphine pellet implantation. Kyotorphin was found to be inactive against column purified enkephalinase A, B and aminopeptidase and indirect evidence would suggest a lack of Met-enkephalin-releasing effect. Thus, kyotorphin represents a unique, naturally occurring peptide with in vivo narcotic-like characteristics and an unknown mechanism of action quite distinct from other opioid peptides.
mesh_terms: D000700:Analgesics; D000818:Animals; D004151:Dipeptides / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D010450:Endopeptidases / Q000378:metabolism; D004723:Endorphins; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D008297:Male; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D015260:Neprilysin; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D000700:Analgesics; D004151:Dipeptides; D004723:Endorphins; C019448:kyotorphin; D009270:Naloxone; D010450:Endopeptidases; D015260:Neprilysin