@article{oai:nagasaki-u.repo.nii.ac.jp:00001581,
 author = {WATANABE, Joe and TOKUYAMA, Shogo and TAKAHASHI, Masakatsu and KANETO, Hiroshi and MAEDA, Mitsuko and KAWASAKI, Koichi and TAGUCHI, Takeo and KOBAYASHI, Yoshiro and YAMAMOTO, Yoshihiro and SHIMOKAWA, Kazuhiro},
 issue = {2},
 journal = {Journal of Pharmacobio-Dynamics},
 month = {},
 note = {The opioid activity and the selectivity for opioid receptor (subtypes) of newly synthesized fluorinated enkephalin (Enk) analogues, [2R, 4R], [2R, 4S], [2S, 4S] and [2S, 4R] trifluoro-Leu5-Enk (KKF-31, 32, 33 and 34) were investigated. The inhibitory effect of KKF-compounds on the electrically induced contractions of guinea-pig ileum (GPI) and mouse vas deferens (MVD) were dosedependent but relatively lower than that of L-Leu5-Enk, except that KKF-34 was rather slightly more potent than L-Leu5-Enk in MVD preparations. In GPI preparations, the pA2 values of naloxone for these compounds were higher than those of naltrindole while the values of naltrindole for KKF-compound were higher than those of naloxone in MVD preparations. Intracerebroventricular KKF-31 and KKF-32 at doses of 20 and 10 nmol/mouse, respectively, produced analgesia comparable to 0.1 nmol Tyr-D-Arg-Phe-Lys-NH2 and 100 nmol Tyr-D-Thr-Gly-Phe-Leu-Thr; however, neither KKF-33 nor 34 produced analgesia up to the doses of 100 nmol/mouse. Both naloxone, 1 mg/kg, i.p., and naltrindole, 10 mg/kg, i.p., antagonized KKF-31- and KKF-32-induced analgesia. The results suggest that the introduction of trifluoromethyl group in Leu5 results in the alternation of the opioid activity and receptor selectivity. Although KKF-33 and KKF-34 possessed a more potent in vitro inhibitory effect than KKF-31 and KKF-32, mediated through μ- and δ-opioid receptors in both preparations, they did not show any appreciable analgesic effect. KKF-31 and KKF-32 produce naloxone-and naltrindole-reversible analgesia irrespective of in vitro μ- and δ-opioid activity., Journal of Pharmacobio-Dynamics, 14(2), pp.101-105; 1991},
 pages = {101--105},
 title = {The opioid activity and receptor selectivity of fluorinated Leu5 Enkephalin analogues in vitro and in vivo.},
 volume = {14},
 year = {1991}
}