THE EFFECT OF FMRF-AMIDE-LIKE PEPTIDES ON ELECTRICAL-ACTIVITY IN ISOLATED MAMMALIAN SPINAL-CORD

FMRFamide and seven FMRFamide-like peptides were manually synthesized on solid phase and their effects tested upon the amplitude of the dors al root-ventral root monosynaptic reflex (MSR) and dorsal horn field p otentials (FP) in an isolated preparation of rat spinal cord. FLFQPQRF amide (NPFF) and AGEGLSSPFWSLAAPQRFamide (NPAF) both depressed a fast component of the FP with similar potencies. FMRFamide also inhibited t he FP but its potency was much lower. NPFF and NPAF potentiated the am plitude of the MSR while FMRFamide had no effect. PQRFamide, PFRFamide , FFRFamide, DPQRFamide and Fmoc-FLFQPQRFamide were also examined on t he MSR. PQRFamide and PFRFamide potentiated the MSR whereas FFRFamide and DPQRFamide caused a small depression at high concentrations. The i ncrease in amplitude of the MSR induced by NPFF was completely abolish ed when the N-terminal was left protected with an Fmoc-group. The resu lts suggest that PFRFamide and PQRFamide may act as agonists of NPFF a nd NPAF whereas the other peptides did not show such activity. (C) 199 8 Elsevier Science Ireland Ltd. All rights reserved.