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Effect of [Hyp6]-dermorphin on spontaneous behaviour and thermoregulation in rats
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almost plateaued thereafter. The ratio of specific to non-specific binding was about 3:1 at 120 rain p.i. Treatment of a schizophrenic patient with a high dose of another substituted benzamide, amisulpride, resulted in a markedly reduced specific tracer uptake in striatal regions. Our results indicate that DMFP is a highly selective PET ligand for quantitative assessment of D2-1ike dopamine receptors, which can be used independently of an on-site cyclotron.
References [1] Muldaerjee J, Yang ZY, Brown T, Roemer J, Cooper M, 1996. 18Fdesmethoxyfallypride: a ttuorine-18 labeled radiotracer with properties similar to carbon-I 1 raclopride for PET imaging studies of dopamine D2 receptors. Life Sci 59: 669-78.
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Positron emission tornography of benzodlazeplne receptors In the human brain with [18F]fluoroethylflumazenll
G. Griinder I , W. H a m k e n s 2, M. Piel2, R. Schirrmacher 2, U. Schmitt I , R. Kleinz I , P. Benz 3, H. Liiddens I , F. R6sch 2. ]DepartmentsofPsychiatry;
2Nuclear Chemistry; 3PET Center, University of Mainz, Germany 5-(2'-[lSF]fluoroethyl)flumazenil (FEF) is a ]8F labeled PET tracer for the central benzodiazepine receptor (1). Compared to the established [HC]flnmazenil, it has the advantage of the longer half-time of the fluorine-18 label. We further optimized its synthesis and evaluated its in vitro receptor affinities and ex vivo biodistribution in mice. Finally, we performed first experiments in humans. FEF was synthesized by fluoroethyltosylation of the desmethyl precursor (Re 15-5528). Radiocbemical yields of about 90% were achieved using DMSO and Nail at 90*(2 already after 10 min. In vitro binding studies were performed with [H-3]Ro 15-4513 in beterologously expressed GABAA receptors of the subunit combinations c(113172 and ct613172. PET studies in two healthy volunteers were performed on a Siemens ECAT EXACT whole-body scanner after injection of 100-208 MBq FEE A second PET scan was conducted in each subject after pretreatment with cold flumazenil (1 mg or 2.5 mg I.V., respectively, 3 min before tracer injection). Brain radioactivity was measured for 60 min p.i. Plasma radioactivity was determined from arterialized venous blood samples. In vitro studies revealed Ki values for the stable ligand of 5.2 + 1.5 nM and 428 + 55 riM, respectively, which indicates the same GABAA receptor subtype selectivity for FEF as for flumazenil. In human brain, maximum accumulation was observed 4 -4- 2 min p.i. with a fast clearance kinetics resulting in 50% and 20% of max. activities at about 10 and 30 min, respectively. FEF uptake followed the known central benzodiazepine receptor distribution in the human brain (occipital cortex > temporal cortex > cerebellum > pens). Pre-treatment with cold flumazenil resulted in significantly reduced specific tracer uptake in all brain areas. Blood clearance peaked at 3 + 1 rain, followed by a second increase of plasma activity at 15 -4- 5 min, the latter probably correlated with the developmant of polar metabolites representing about 5% of the total activity at 5 min and about 75% at 30 min p.i. Our results indicate that FEF is a suitable PET ligand for quantitative assessment of central benzodiazepine receptors, which can be used independently of an on-site cyclotron.
References [1] Moerlein SM, Perlmutter JS, 1992. Binding of 5-(2C[18F]fluorocthyl)flumazenil to central benzodiazepine receptors measured in living baboon by positron emission tomography. Eur J Pharmacol 218, 109-115.
II-'.U.UUUI Effect of [Hyp6]-dermorphin on spontaneous behavlour and thermoregulatlon in rata A.P. Bonartsev 2, M.G. Uranova 2, T.G. Emel'yanova 1, A.B. Usenko 1, A.A. Kamensky 2, L.A. Andreeva3, L.Y. Alfeeva3. IN.N. Semenoo Institute of Chemical Physics RAS, Departument of Matter Structure, Moscow," 2Lomonoso~ Moscow State University, Departument of Human and Animal Phisiology, Moscow; ~Institute of Molecular Genetics RAS, Moscow, Russia Natural opioid peptide dermorphin (DM) possessing a wide spectrum of physiological activity produces changes in animals nociception, heart rate, blood pressure, respiration, thermoregnlation, behaviour ets. The effect of natural dermorphin analogue [Hyp6]-dermorphin (Tyr-D-AlaPbe-Gly-Tyr-Hyp-Ser) (HDM) on different forms of rat behaviour and on rat thermoregulatury responses were studied by using the next methods. Spontaneous behaviour was estimated in "Hole-board" and "OptoVarimex" tests [1]. The core temperature and tail skin temperature responses were measured in the cold environment (4-7 grad. C) and in the thermoneutral environment (27-28 grad. C) by using copper-nickel thermocouples [2]. All values were compared to the control values. The statistical significance of differences between the control and HDMtreated groups was verified by means of a nonpammetric Mann-Whitney U-test and t-test [1, 2]. Data obtained demonstrate that HDM when injected i.p. at a dose of 500 micrograms/kg body weight caused a significant (p = 0.05) decrease in rats vertical and horizontal locomotor activities in "Opto-Varimex" test. This effect was continuous during the period of 30 min after i.p. injection. When injected 20 min prior the testing in "Hole-board" HDM induced a significant (p < 0.01) decrease in horizontal locomotion and in orientative-trying reaction, inhibiting both hole-poking and rearing in rats. At the same dose in the cold environment HDM caused a significant (p < 0.05), long-term (80 min) decrease in core temperature with the maximum (1.4 grad. C) at 20 min after i.p. injection without any effects on tail skin temperature. In the thermoneutral environment HDM also evoked a significant (p < 0.05), but weak (0.4 grad. C) and short-term (20 min) hypothermic response that was accompanied by short-term (10 min) peripheral vasodilatation. Data obtained allow to assume that natural dermorphin analogue HDM has an inhibitory effect on rat spontaneous behaviour (locomotion and orientative-trying reaction) that is accompanied by autonomic responses (hypotbermia and peripheral vasodilatation). These physiological effects of HDM are similar but less pronounced than the effects of dermorphin [1, 2].
References [I] Makanjuola R., Hill G., D e w C., Campbell G. and Asshcrofl G. The effectsof psyehotropic drugs on exploratory and stereotyped behaviour of rats studied on a Hole-Board//Psychopharmacology. 1977. v.55. p.67-74. [2] T. G. Emel'yanova, A. B. Usenko, V. I. Deigin, E. P. Yarova, A. A. Kamcnsky. Effect of dermorphin on thermorcgulation in rats at selected ambient temperatures. Peptidas,Vol. 17, No. 2, pp. 241-245, 1996.
t?.6 Other topics
almost plateaued thereafter. The ratio of specific to non-specific binding was about 3:1 at 120 rain p.i. Treatment of a schizophrenic patient with a high dose of another substituted benzamide, amisulpride, resulted in a markedly reduced specific tracer uptake in striatal regions. Our results indicate that DMFP is a highly selective PET ligand for quantitative assessment of D2-1ike dopamine receptors, which can be used independently of an on-site cyclotron.
References [1] Muldaerjee J, Yang ZY, Brown T, Roemer J, Cooper M, 1996. 18Fdesmethoxyfallypride: a ttuorine-18 labeled radiotracer with properties similar to carbon-I 1 raclopride for PET imaging studies of dopamine D2 receptors. Life Sci 59: 669-78.
•
Positron emission tornography of benzodlazeplne receptors In the human brain with [18F]fluoroethylflumazenll
G. Griinder I , W. H a m k e n s 2, M. Piel2, R. Schirrmacher 2, U. Schmitt I , R. Kleinz I , P. Benz 3, H. Liiddens I , F. R6sch 2. ]DepartmentsofPsychiatry;
2Nuclear Chemistry; 3PET Center, University of Mainz, Germany 5-(2'-[lSF]fluoroethyl)flumazenil (FEF) is a ]8F labeled PET tracer for the central benzodiazepine receptor (1). Compared to the established [HC]flnmazenil, it has the advantage of the longer half-time of the fluorine-18 label. We further optimized its synthesis and evaluated its in vitro receptor affinities and ex vivo biodistribution in mice. Finally, we performed first experiments in humans. FEF was synthesized by fluoroethyltosylation of the desmethyl precursor (Re 15-5528). Radiocbemical yields of about 90% were achieved using DMSO and Nail at 90*(2 already after 10 min. In vitro binding studies were performed with [H-3]Ro 15-4513 in beterologously expressed GABAA receptors of the subunit combinations c(113172 and ct613172. PET studies in two healthy volunteers were performed on a Siemens ECAT EXACT whole-body scanner after injection of 100-208 MBq FEE A second PET scan was conducted in each subject after pretreatment with cold flumazenil (1 mg or 2.5 mg I.V., respectively, 3 min before tracer injection). Brain radioactivity was measured for 60 min p.i. Plasma radioactivity was determined from arterialized venous blood samples. In vitro studies revealed Ki values for the stable ligand of 5.2 + 1.5 nM and 428 + 55 riM, respectively, which indicates the same GABAA receptor subtype selectivity for FEF as for flumazenil. In human brain, maximum accumulation was observed 4 -4- 2 min p.i. with a fast clearance kinetics resulting in 50% and 20% of max. activities at about 10 and 30 min, respectively. FEF uptake followed the known central benzodiazepine receptor distribution in the human brain (occipital cortex > temporal cortex > cerebellum > pens). Pre-treatment with cold flumazenil resulted in significantly reduced specific tracer uptake in all brain areas. Blood clearance peaked at 3 + 1 rain, followed by a second increase of plasma activity at 15 -4- 5 min, the latter probably correlated with the developmant of polar metabolites representing about 5% of the total activity at 5 min and about 75% at 30 min p.i. Our results indicate that FEF is a suitable PET ligand for quantitative assessment of central benzodiazepine receptors, which can be used independently of an on-site cyclotron.
References [1] Moerlein SM, Perlmutter JS, 1992. Binding of 5-(2C[18F]fluorocthyl)flumazenil to central benzodiazepine receptors measured in living baboon by positron emission tomography. Eur J Pharmacol 218, 109-115.
II-'.U.UUUI Effect of [Hyp6]-dermorphin on spontaneous behavlour and thermoregulatlon in rata A.P. Bonartsev 2, M.G. Uranova 2, T.G. Emel'yanova 1, A.B. Usenko 1, A.A. Kamensky 2, L.A. Andreeva3, L.Y. Alfeeva3. IN.N. Semenoo Institute of Chemical Physics RAS, Departument of Matter Structure, Moscow," 2Lomonoso~ Moscow State University, Departument of Human and Animal Phisiology, Moscow; ~Institute of Molecular Genetics RAS, Moscow, Russia Natural opioid peptide dermorphin (DM) possessing a wide spectrum of physiological activity produces changes in animals nociception, heart rate, blood pressure, respiration, thermoregnlation, behaviour ets. The effect of natural dermorphin analogue [Hyp6]-dermorphin (Tyr-D-AlaPbe-Gly-Tyr-Hyp-Ser) (HDM) on different forms of rat behaviour and on rat thermoregulatury responses were studied by using the next methods. Spontaneous behaviour was estimated in "Hole-board" and "OptoVarimex" tests [1]. The core temperature and tail skin temperature responses were measured in the cold environment (4-7 grad. C) and in the thermoneutral environment (27-28 grad. C) by using copper-nickel thermocouples [2]. All values were compared to the control values. The statistical significance of differences between the control and HDMtreated groups was verified by means of a nonpammetric Mann-Whitney U-test and t-test [1, 2]. Data obtained demonstrate that HDM when injected i.p. at a dose of 500 micrograms/kg body weight caused a significant (p = 0.05) decrease in rats vertical and horizontal locomotor activities in "Opto-Varimex" test. This effect was continuous during the period of 30 min after i.p. injection. When injected 20 min prior the testing in "Hole-board" HDM induced a significant (p < 0.01) decrease in horizontal locomotion and in orientative-trying reaction, inhibiting both hole-poking and rearing in rats. At the same dose in the cold environment HDM caused a significant (p < 0.05), long-term (80 min) decrease in core temperature with the maximum (1.4 grad. C) at 20 min after i.p. injection without any effects on tail skin temperature. In the thermoneutral environment HDM also evoked a significant (p < 0.05), but weak (0.4 grad. C) and short-term (20 min) hypothermic response that was accompanied by short-term (10 min) peripheral vasodilatation. Data obtained allow to assume that natural dermorphin analogue HDM has an inhibitory effect on rat spontaneous behaviour (locomotion and orientative-trying reaction) that is accompanied by autonomic responses (hypotbermia and peripheral vasodilatation). These physiological effects of HDM are similar but less pronounced than the effects of dermorphin [1, 2].
References [I] Makanjuola R., Hill G., D e w C., Campbell G. and Asshcrofl G. The effectsof psyehotropic drugs on exploratory and stereotyped behaviour of rats studied on a Hole-Board//Psychopharmacology. 1977. v.55. p.67-74. [2] T. G. Emel'yanova, A. B. Usenko, V. I. Deigin, E. P. Yarova, A. A. Kamcnsky. Effect of dermorphin on thermorcgulation in rats at selected ambient temperatures. Peptidas,Vol. 17, No. 2, pp. 241-245, 1996.