Dopamine receptor antagonists block the effect of Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) on the opiate form of footshock-induced analgesia.
Previous studies have shown that some of CNS actions of an endogenous peptide Tyr-MIF-1, are mediated by dopamine (DA) receptors. To study the effect of DA receptor blockade on the antiopiate properties of Tyr-MIF-1, the opiate form of footshock-induced analgesia was elicited in the rat. The nociceptive responses were determined using the hot-plate test (52.5 degrees C). Intraperitoneal pre-treatment with haloperidol (500 micrograms/kg), SCH 23390 (150 micrograms/kg), or spiroperidol (150 micrograms/kg) potentiated the antinociceptive effect of the footshock and blocked the antagonistic action of Tyr-MIF-1 (200 micrograms/kg and 2.0 mg/kg). A dose of haloperidol too small to potentiate the antinociceptive effect of the footshock (100 micrograms/kg) was still able to block the action of Tyr-MIF-1 (200 micrograms/kg). The results suggest that activation of DA receptors mediates the antagonizing effect of Tyr-MIF-1 on the opiate form of footshock-induced analgesia in the rat.
Department of Medicine, Tulane University School of Medicine, New Orleans, LA 70146.
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Krowicki
D000595:Amino Acid Sequence; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D018492:Dopamine Antagonists; D004357:Drug Synergism; D005528:Foot; D006220:Haloperidol / Q000494:pharmacology; D006358:Hot Temperature; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D009270:Naloxone / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000502:physiology*; D013134:Spiperone / Q000494:pharmacology; D004561:Transcutaneous Electric Nerve Stimulation
D001552:Benzazepines; D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; D009270:Naloxone; D013134:Spiperone; C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone; D006220:Haloperidol