PULSATILE SECRETION OF NEUROPEPTIDE FF INTO HUMAN BLOOD

Neuropeptide FF (NPFF) is a peptide with opioid modulating and cardioe xcitatory effects, it is present in the central nervous system and in the periphery of several mammalian species. Using a sensitive and spec ific radioimmunoassay for NPFF-like immunoreactivity (NPFFir) we obser ved that the peptide concentration fluctuated in a pattern compatible with pulsatile secretion of the peptide in human blood. When NPFF samp les were collected every 2 or 5 min for a 95 min period in healthy vol unteers the basal NPFF concentration in human blood was 2.2 +/- 0.5 pg /ml and the NPFF pulses (14.6 +/- 10.6 pg/ml) represented a 526 +/- 28 0% increase over baseline. The NPFF pulses where short, suggesting a r apid degradation of NPFF in the circulation. We observed no twenty-fou r hour rhythm of NPFF in human blood when NPFF samples were taken duri ng one day every four hours. Fluctuations in NPFF levels found in the 95 min and the 24 h studies did not correlate with plasma vasopressin levels. Our study did not support the concept that vasopressin and NPF F may be co-released from the pituitary. However, the pulsatile charac ter of NPFF secretion in itself suggests a biologic role for neuropept ide FF in humans. (C) 1998 Elsevier Science Inc.