PRESENCE OF NEUROPEPTIDE FF RECEPTORS ON PRIMARY AFFERENT-FIBERS OF THE RAT SPINAL-CORD

A radioiodinated analogue of neuropeptide FF, [I-125][D.Tyr(1), (NMe)P he(3)]neuropeptide FF, was used as a selective probe to label neuropep tide FF receptors in the rat spinal cord. Following neonatal capsaicin treatment, dorsal rhizotomy or sciatic nerve section, the distributio n and possible alterations of spinal cord specific [I-125][D.Tyr(1), ( NMe)Phe(3)]neuropeptide FF binding sites were evaluat ed using in vitr o quantitative receptor autoradiography. In normal rats, the highest d ensities of sites were observed in the superficial layers of the dorsa l horn (laminae I-II) whereas moderate to low amounts of labelling wer e seen in the deeper (III-VI) laminae, around the central canal, and i n the ventral horn. Capsaicin-treated rats showed a bilateral decrease (47%) in [I-125][D.Tyr(1), (NMe)Phe(3)]neuroeptide FF binding in all spinal areas. Unilateral sciatic nerve section and unilateral dorsal r hizotomy induced significant depletions (15-27%) in [I-125][D.Tyr(1), (NMe)Phe(3)]neuropeptide FF labelling in the ipsilateral dorsal horn. These results suggest that a proportion of neuropeptide FF receptors i s located on primary afferent terminals of the dorsal horn and could t hus play a role in the modulation of nociceptive transmission. Copyrig ht (C) 1996 IBRO.