Actions of intracerebroventricular administration of kyotorphin and an analog on thermoregulation in the mouse.
Intracerebroventricular (ICV) administration of kyotorphin (L-Tyr-L-Arg) and cyclo (N-methyl-L-Tyr-L-Arg), its analog, produced significant dose-dependent hypothermic responses in mice at an ambient temperature of 24 degrees C. The hypothermic action of kyotorphin was much greater than that of Met-enkephalin (Met-ENK) but less than that of cyclo NMTA. This action was slightly but not significantly reversed by intraperitoneally administered naloxone (8 mg/kg), an opioid receptor antagonist. Met-ENK utilized as a control peptide in this study also produced a dose-dependent hypothermia which was slightly antagonized by naloxone (8 mg/kg, IP). Thyrotropin releasing hormone (TRH) injected ICV produced hyperthermia dose-dependently. The hypothermia induced by kyotorphin, its cyclic analog and Met-ENK was prevented by a small dose of TRH (0.18 microgram = 0.5 nmol/animal) which by itself had little effect on body temperature. A TRH neuronal system in the brain may explain the mechanism of kyotorphin-induced hypothermia. However, there was little evidence of involvement of opioid receptors. The present study demonstrates a potent action of kyotorphin and its analog on thermoregulation.
D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D004723:Endorphins / Q000008:administration & dosage / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009270:Naloxone / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000008:administration & dosage / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D000700:Analgesics; D004723:Endorphins; D010456:Peptides, Cyclic; D010879:Piperazines; C019448:kyotorphin; D009270:Naloxone; D004744:Enkephalin, Methionine; D013973:Thyrotropin-Releasing Hormone; C039517:cyclo(N-methyltyrosylarginyl); C015924:histidyl-proline diketopiperazine