New central projections of neuropeptide FF: colateral branching pathways in the brainstem and hypothalamus in the rat

Neuropeptide FF (NPFF), a morphine modulatory peptide, has been identified within discrete autonomic regions in the brainstem and hypothalamus. Triple fluorescence labelling was employed to identify collateral branching proje ctions of NPFF neurons located within the nucleus tractus solitarius (NTS) and in the region of the hypothalamus between the dorsomedial and ventromed ial hypothalamus. Injections of two retrograde tracers, rhodamine- and fluo rescein-labelled latex microspheres into the pontine parabrachial nucleus ( PBN) and the ventrolateral medulla resulted in labelling of NPFF neurons in the NTS that contained one (double-labelled) or both (triple-labelled) tra cers. Within the NTS, most double- and triple-labelled NPFF neurons were lo calized at the level of the area postrema or just rostral to it and within the medial and dorsomedial subdivisions of the nucleus. Injections of trace rs into the PEN and hypothalamic paraventricular nucleus revealed double- a nd triple-labelled NPFF neurons, a majority of which were located in a zone between the dorsomedial acid ventromedial hypothalamus. These results indi cate that NPFF neurons in the brainstem and hypothalamus may simultaneously transmit signals to their target nuclei in the brainstem and forebrain. Th is coordinated signalling may lead to synchronized responses of NPFF target sites and provide insights into the role of this peptide in cardiovascular and nociceptive responses. (C) 2001 Elsevier Science B.V. All rights reser ved.