Hypothermic effects of neuropeptide FF analogues in mice

The effects of neuropeptide FF (NPFF) and its analogues on mouse body temperature were examined. In a thermoneutral environment, administration of NPFF (Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2), 1DMe ([D.Tyr(1), (N.Me)Phe(3)] NPFF), and 3D ([D.Tyr(1), D.Leu(2), D.Phe(3)] NPFF) in the third ventricle produced marked hypothermia. The effect of 1DMe was dose-dependent, and 45 nmol decreased body temperature by 5.6 degrees C. This effect was more pronounced when mice were placed at 4 degrees C. Hypothermia was not reversed by naloxone, an opioid antagonist, and was not modified by morphine. After 5 days of chronic treatment with 1DMe, mice did not became tolerant to the hypothermic effect. These results indicate that central NPFF receptors may control body temperature independently from opioid functions. (C) 1997 Elsevier Science Inc.