title: MIF-1 and Tyr-MIF-1 antagonize morphine and opioid but not non-opioid stress-induced analgesia in the snail, Cepaea nemoralis.
abstract: The effects of prolyl-leucyl-glycinamide (MIF-1, PLG), tyrosine-prolyl-leucyl-glycinamide (Tyr-MIF-1, YPLG) and naloxone on morphine and warm and cold stress-induced increases in the latency of the thermal (40 degrees C hot plate) avoidance behaviors of the terrestrial snail, Cepaea nemoralis, were examined. All three substances blocked the morphine- and warm stress-induced opioid analgesia, while having no effects on non-opioid cold stress-induced analgesia. Tyr-MIF-1 had a significantly greater inhibitory effect than MIF-1. These results indicate that MIF-1 and Tyr-MIF-1 antagonize the antinociceptive effects of exogenous opiates and opioid-mediated analgesia in snails in a manner analogous to that described for mammals. This raises the possibility of an evolutionary conservation of functional opioid antagonists.
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D003080:Cold Temperature; D006358:Hot Temperature; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D011930:Reaction Time; D012908:Snails / Q000502:physiology*; D013312:Stress, Physiological / Q000503:physiopathology*
chemical_list: D009270:Naloxone; D009020:Morphine; C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone