nitroarginine and phenylalanyl-leucyl-phenylalanyl-glutaminyl-prolyl-glutaminyl-arginyl-phenylalaninamide

Neuropeptide FF (NPFF) and NPVF, two closely NPFF related peptides, have different affinities for the two NPFF receptors (NPFF1 and NPFF2). To assess the peripheral effects of NPFF receptors in the gastrointestinal tract motility, NPFF and NPVF were tested in the mouse isolated distal colon. Both NPFF (1-15 microM) and NPVF (1-15 microM) dose-dependently caused significant colonic contractions. Pre-treatment with the putative NPFF antagonist, BIBP3226 (30 microM) abolished the contractile responses to the two neuropeptides (3 microM). They had no additional contractile activities in colonic preparations contracted by Nomega-nitro-L-arginine (30 microM). Moreover, the contractions of these two neuropeptides were weakened by L-arginine (2 mM). The responses to NPFF (5 microM) and NPVF (5 microM) were not modified by atropine or naloxone (1 microM). Furthermore, NPFF (1 microM) and NPVF (1 microM) did not influence the contractive responses to acetylcholine (0.1-10 microM), morphine (1 microM) or nociceptin (0.1 microM). These data suggest that NPFF and NPVF cause contractions of the mouse distal colon via their NPFF receptors and this effect is mediated by NO but not by cholinergic pathways, independently from opioid system. In addition, the isolated bioassay may be applied as a simple parameter to characterize the potential NPFF agonists and antagonists.

Topics: Acetylcholine; Animals; Arginine; Biological Assay; Colon, Sigmoid; Enzyme Inhibitors; In Vitro Techniques; Mice; Muscle Contraction; Neuropeptides; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oligopeptides; Receptors, Neuropeptide

Neuropeptide FF (NPFF) has certain antiopiate actions and may play a role in opiate tolerance and dependence. Third ventricle injection of 10 micrograms NPFF induces a quasimorphine abstinence syndrome in opiate-naive rats. Nitric oxide synthesis may also contribute to opiate tolerance and dependence. The present study tests the hypothesis that NPFF acts through stimulation of nitric oxide synthase (NOS). Third ventricular injection of 10 micrograms NPFF precipitated an average of 46 abstinence-like signs during a 20-min observation. Pretreatment (30 min earlier) with 7.5 or 15 mg/kg s.c. of the NOS inhibitor nitro-L-arginine (L-NNA) resulted in a significant and dose-dependent alleviation of NPFF-induced abstinence-like signs. The anti-NPFF activity of 15 mg/kg L-NNA was blocked by 750 mg/kg L-arginine, but not by the same amount of D-arginine, indicating that L-NNA attenuates NPFF activity through a stereospecific inhibition of NOS.

Topics: Animals; Arginine; Cerebral Ventricles; Enzyme Inhibitors; Injections, Intraventricular; Male; Narcotic Antagonists; Nitric Oxide Synthase; Nitroarginine; Oligopeptides; Rats; Rats, Sprague-Dawley; Stereoisomerism; Stereotyped Behavior; Substance Withdrawal Syndrome