title: Similar antagonism of morphine analgesia by MIF-1 and naloxone in Carassius auratus.
abstract: Prolyl-leucyl-glycinamide (MIF-1), the C-terminal tripeptide of oxytocin, and naloxone were administered intracranially (IC) to goldfish (Carassius auratus) in doses of 0.001, 0.01, 0.1, 1.0 and 10.0 mg/kg and compared to a diluent control group for their ability to reduce the effects of morphine (30 mg/kg IC) in an assay measuring analgesia to electric shock. Threshold levels of pain were determined by the voltage necessary to produce an agitated swimming response (ASR). Both MIF-1 and naloxone were found to significantly reduce the analgesic effects of morphine when compared to the diluent control group. Similar dose-response curves in an apparent sine-wave pattern were noted with both MIF-1 and naloxone when comparisons were made both at 20 minutes after administration of morphine and over the entire 150 minutes of the experiment. The results support the evidence that MIF-1 can act as an opiate antagonist.
mesh_terms: D000698:Analgesia; D000818:Animals; D004336:Drug Antagonism; D004597:Electroshock; D006054:Goldfish; D007700:Kinetics; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology
chemical_list: D009270:Naloxone; D009020:Morphine; D009075:MSH Release-Inhibiting Hormone