Tadayoshi Takeuchi1,*, Akikazu Fujita1,2, Michel Roumy3, Jean-Marie Zajac3 and Fumiaki Hata1,2
1Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Science and 2Department of Molecular Physiology and Biochemistry, Research Institute for Advanced Science and Technology, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
3Institut de Pharmacologie et de Biologie Structurale, C.N.R.S., 205 Route de Narbonne, 31077 Toulouse cedex, France
*Corresponding author. FAX: +81-722-54-9480, E-mail: email@example.com
Abstract: Since neuropeptide FF (NPFF) is a putative neurotransmitter to exert anti-opioid activity, we examined the effects of [D-Tyr1, (NMe)Phe3]neuropeptide FF (1DMe), a stable NPFF analog, on acetylcholine (ACh) release from a longitudinal muscle-myenteric plexus (LMMP) preparation of guinea pig ileum in which opioids were known to inhibit ACh release when muscarinic autoinhibition was not fully activated. In the presence of atropine, 1DMe increased spontaneous and electrical field stimulation (EFS)-evoked ACh release in a concentration-dependent manner. Naloxone also increased ACh release. The stimulatory effects of 1DMe and naloxone were not additive. In the absence of atropine, 1DMe did not affect ACh release. Morphine decreased spontaneous and EFS-evoked ACh release in the presence of 1 mM atropine. 1DMe as well as naloxone counteracted the inhibitory effects of morphine on EFS-evoked ACh release. The combination of 1DMe and naloxone was not more inhibitory than either drug alone. 1DMe had no appreciable effect on norepinephrine-induced inhibition of spontaneous and EFS-evoked ACh release. These results first demonstrated the effects of a NPFF analog on neurotransmitter release: 1DMe had a stimulatory effect on spontaneous and EFS-induced ACh release from the LMMP preparation of guinea pig ileum, probably by counteracting the inhibitory effect of endogenous opioids on ACh release.
Keywords: Neuropeptide FF, Acetylcholine release, Morphine, Muscarinic autoinhibition, Myenteric plexus
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